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Habitat, population and leaf characteristics of Zostera marina L. on Roberts Bank, British Columbia Moody, Robert 1978

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HABITAT, POPULATION AND LEAF. CHARACTERISTICS OF  Zostera  marina  L . ON  ROBERTS BANK, BRITISH COLUMBIA by  ROBERT MOODY B.Sc,  U n i v e r s i t y o f B r i t i s h C o l u m b i a , 1975  A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE FACULTY OF GRADUATE Department o f P l a n t  We a c c e p t  this  STUDIES  Science  t h e s i s as conforming  to the required  standard  THE UNIVERSITY OF BRITISH COLUMBIA May, 19 78  © R O B E R T MOODY, 1978  In p r e s e n t i n g t h i s  thesis  in p a r t i a l  f u l f i l m e n t o f the requirements f o r  an advanced degree at the U n i v e r s i t y of B r i t i s h Columbia, the I  Library shall  f u r t h e r agree  for  that permission  r e f e r e n c e and study.  f o r e x t e n s i v e copying o f t h i s  this  representatives. thesis  It  thesis  i s understood that copying o r p u b l i c a t i o n  f o r f i n a n c i a l gain shall  written permission.  Department of The  Plant  Date  Science  U n i v e r s i t y of B r i t i s h  2075 Wesbrook Place Vancouver, Canada V6T 1W5  5  for  that  s c h o l a r l y purposes may be granted by the Head of my Department or  by h i s of  make i t f r e e l y a v a i l a b l e  I agree  May 1. 1978  Columbia  not be allowed without my  ii ABSTRACT  The  s a n d and mud  shore support marina  L.  (eelgrass).  recreational areas. and on  extensive  o f the F r a s e r River  meadows o f t h e s e a g r a s s Industrial,  developments t h r e a t e n  A study  population southern  flats  was  undertaken  Zostera  residential these  and  valuable  i n t o the h a b i t a t  and m o r p h o l o g i c a l  R o b e r t s Bank, B r i t i s h  fore-  characteristics  foreshore  requirements of eelgrass  Columbia t o p r o v i d e  i n f o r m a t i o n which would h e l p minimize the p o t e n t i a l l y d e l e t e r i o u s e f f e c t s o f s u c h d e v e l o p m e n t s on t h e e e l g r a s s resource. Wate r t e m p e r a t u r e s and s a l i n i t i e s c  on  southern  R o b e r t s Bank a l l a p p r o a c h t h e w o r l d - w i d e  for eelgrass.  The u p p e r d i s t r i b u t i o n a l  lower than those  of other  The  o f the substrate  sandy n a t u r e  Pacific  limit  tional the  Light availability limit  of eelgrass  sandy s u b s t r a t e  turbid  southern  Roberts  and r e d u c e d l i g h t  of eelgrass distribu-  T h e s e two f a c t o r s ,  availability River  i n the  foreshore,  appear on  Bank.  determine seasonal and l e a f  populations.  f o r the narrow depth range o f e e l g r a s s  A stratified  density  limit  areas.  e s t u a r i n e waters o f the F r a s e r  t o be r e s p o n s i b l e  was  influences "desiccation"  determines the lower  i n other  optima  of eelgrass  Coast eelgrass  which, i n t u r n , c o n t r o l s the i n t e r t i d a l growth.  and wave m o t i o n  random s a m p l i n g  changes i n e e l g r a s s  dimensions a t f i v e  technique  was  standing  crop,  used t o turion  elevations, located at  0.5 m d e p t h i n t e r v a l s , f r o m t h e u p p e r t o t h e l o w e r l i m i t s o f eelgrass  growth.  A pronounced d e c l i n e  i n both t u r i o n  density  and  l e a f standing  crop occurred  i n l a t e summer.  Throughout  the  study p e r i o d ,  l e a f standing  c r o p s and t u r i o n  densities  were g r e a t e s t ' a t  the three  Reduced l e a f s t a n d i n g  intermediate  c r o p s was f o u n d  d e n s i t i e s were a l s o limits  of eelgrass  elevations.  c r o p s were f o u n d n e a r t h e u p p e r and  lower edges o f t h e e e l g r a s s standing  study  b e d ; no s i g n i f i c a n t d i f f e r e n c e i n  f o r these  two e l e v a t i o n s .  l o w e r n e a r t h e u p p e r and l o w e r and a s i g n i f i c a n t d i f f e r e n c e  lowest t u r i o n d e n s i t y  depth  i n turion  d e n s i t i e s was f o u n d between t h e s e two e l e v a t i o n s ,  grass.  Turion  with the  r e c o r d e d near the lower l i m i t  N e a r t h e u p p e r edge o f t h e e e l g r a s s  w e i g h t s and mean l e a f l e n g t h s  were o n e - h a l f  of eel-  bed, t u r i o n those o f t h e lower  elevations. " A that  synthesis  depth-related  morphological  of the a v a i l a b l e information  factors  strongly  and p o p u l a t i o n  southern Roberts  Bank.  influence  indicates  certain  c h a r a c t e r i s t i c s of eelgrass  on  iv TABLE OF CONTENTS Page 1.  INTRODUCTION  1  1.1.  Purpose o f the Study  1  1.2.  Previous  2  1.3.  Objectives  Research o f the Study  9  2.  THE STUDY AREA  10  3.  ENVIRONMENTAL FACTORS IN RELATION EELGRASS HABITAT 3.1.  Materials  3.2.  Habitat 3.2.1.  and Methods  17  Factors  21  Salinity  21  S e a s o n a l Changes  21  3.2.1.2.  D i u r n a l Changes  24  Temperature  24  3.2.2.1.  S e a s o n a l Changes  24  3.2.2.2.  D i u r n a l Changes  27  3.2.3.  Light  27  3.2.3.1.  S e a s o n a l Changes  27  3.2.3.2.  D i u r n a l Changes  27  3.2.4. 3.2.5.  Tidal  3.2.6.  Range and P e r c e n t a g e  Exposure  32  Substrate  33  3.2.5.1. 3.2.5.2.  4.  17  3.2.1.1. 3.2.2.  3.3.  TO  S u r f a c e L e v e l Changes P h y s i c a l and C h e m i c a l Characteristics  33 33  Waves and C u r r e n t s  39  Discussion  39  STANDING CROP, TURION DENSITY, LEAF MEASUREMENT STUDIES 4.1.  Materials  4.2.  Standing  and M e t h o d s Crop  BIOMASS  AND 45 45 48  4.2.1.  T e m p o r a l Changes  50  4.2.2.  Influence  52  o f Depth  V  Page 4.3.  Turion 4.3.1. 4.3.2.  5.  Density  56  I n f l u e n c e o f Time and E l e v a t i o n on T o t a l T u r i o n D e n s i t y  56  I n f l u e n c e o f Time and E l e v a t i o n on R e p r o d u c t i v e T u r i o n D e n s i t y ...  64  4.4.  The I n f l u e n c e o f D e p t h on Weight p e r T u r i o n  4.5.  Biomass  70  4.6.  L e a f Measurements  70  4.7.  Discussion  75  SUMMARY AND CONCLUSIONS  Organic  64  7  9  GLOSSARY  83  BIBLIOGRAPHY  86  APPENDICES ..  91  vi L I S T OF TABLES Table  Page  1.  Particle  2.  O r g a n i c and c a r b o n a t e c a r b o n sediments  3.  4.  5.  6.  7.  8.  9.  10.  11.  12.  size  composition  Comparisons o f h a b i t a t grass growth ( m o d i f i e d P h i l l i p s 1972)  o f sediments contents  36 of 40  factors affecting eelf r o m S t o u t 1976, and 41  A n a l y s i s o f v a r i a n c e summary t a b l e f o r mean l e a f standing crop (organic dry weight i n grams p e r 0.25 s q u a r e m e t e r q u a d r a t )  51  Newman-Keuls M u l t i p l e Range T e s t f o r mean l e a f s t a n d i n g s t o c k s ( o r g a n i c d r y w e i g h t i n grams p e r 0.2 5 s q u a r e m e t e r q u a d r a t ) a t f i v e elevations  55  Analysis of variance total turion density meter quadrat  58  summary t a b l e f o r mean ( t u r i o n s p e r 0.25 s q u a r e  Newman-Keuls M u l t i p l e Range T e s t f o r t o t a l t u r i o n d e n s i t y ( t u r i o n s p e r 0.25 s q u a r e m e t e r q u a d r a t ) means a t f i v e e l e v a t i o n s  59  T o t a l t u r i o n d e n s i t i e s ( t u r i o n s p e r 0.25 square meter quadrat) f o r f o u r t e e n sampling s e s s i o n s , May t o December 1976  61  A n a l y s i s o f v a r i a n c e summary t a b l e f o r mean reproductive turion density (turions per square meter)  65  Linear regression equations of organic dry w e i g h t (g) on t u r i o n numbers p e r q u a d r a t f o r five elevations  66  A n a l y s i s o f c o v a r i a n c e summary t e s t i n g f o r s i g n i f i c a n t d i f f e r e n c e s between s l o p e s o f l i n e a r r e g r e s s i o n l i n e s o f organic dry weight on t u r i o n numbers f o r f i v e e l e v a t i o n s  68  Newman-Keuls M u l t i p l e Range T e s t f o r d i f f e r e n c e s between s l o p e s o f l i n e a r r e g r e s s i o n s o f o r g a n i c d r y w e i g h t on t u r i o n numbers f o r f i v e elevations  69  vii Table 13.  14. 15.  Page Percentages of above-substrate (leaf) b e l o w - s u b s t r a t e ( r o o t s and r h i z o m e s ) s t a n d i n g c r o p s , A p r i l 1976 t o J a n u a r y  and 1977  ...  71  L e a f measurements f o r f i v e e l e v a t i o n s , A u g u s t 1976 t o J a n u a r y 1977  72  L e a f and r h i z o m e measurements f o r s a m p l e s c o l l e c t e d a t 0.8 m e t e r s ( i n r e l a t i o n t o C h a r t Datum), A u g u s t 19 76 t o J a n u a r y 19 77. Number of observations i n brackets  74  viii LIST  OF  FIGURES  Figure 1. 2.  3.  4.  5.  6.  7.  8.  9.  10.  Page  A e r i a l photo mosaic o f the F r a s e r R i v e r D e l t a showing l o c a t i o n o f t h e s t u d y a r e a  11,12  Diagram o f the study s i t e locations  13,14  showing  transect  Schematic p r o f i l e o f t h e s t u d y s i t e showing transect elevations i n r e l a t i o n to Chart Datum  18,19  S u r f a c e and 1.5 m s a l i n i t i e s and t e m p e r a t u r e s a t t h e s t u d y s i t e and mean m o n t h l y a i r t e m p e r ature a t Vancouver I n t e r n a t i o n a l A i r p o r t (Monthly Record, M e t e o r o l o g i c a l O b s e r v a t i o n s i n Canada, A t m o s p h e r i c Environment, F i s h e r i e s and E n v i r o n m e n t C a n a d a , A p r i l 19 76 t o ^ J a n u a r y 19 7 7 ) . Mean m o n t h l y a i r t e m p e r a t u r e p l o t t e d a t t h e m i d p o i n t o f e a c h month  22,23  D i u r n a l s u r f a c e and 1.5 m s a l i n i t i e s . J u l y 2 8 a n d O c t o b e r 4, 19 76. January 1977 :  25,26  May 18,  2,  D i u r n a l a i r t e m p e r a t u r e s and s u r f a c e and 1.5 m water temperatures. May 2, J u l y 2 8 and O c t o b e r 4, 1976. J a n u a r y 18, 1977  28,29  S e c c h i d e p t h (meters) a t t h e s t u d y s i t e and maximum d a i l y d i s c h a r g e ( t h o u s a n d s o f c u b i c m e t e r s p e r second) o f t h e F r a s e r R i v e r a t Hope, B.C. f o r e a c h month f r o m M a r c h 19 76 t o J a n u a r y 1977  30,31  Net o s c i l l a t i o n s o f sediment s u r f a c e l e v e l s , J u l y 1976 t o J a n u a r y 1977. Mean + S t a n d a r d Error  34,35  S e d i m e n t samples t a k e n a t 10-meter i n t e r v a l s from t h e upper t o t h e lower l i m i t s o f e e l g r a s s growth: a. Percentage of f i n e s b. P e r c e n t a g e s o f o r g a n i c and c a r b o n a t e carbon  37,38  Mean l e a f s t a n d i n g c r o p (grams p e r s q u a r e meter) f o r f i v e e l e v a t i o n s ( i n r e l a t i o n t o C h a r t Datum), A p r i l 1976 t o J a n u a r y 1977  53,54  ix Figure 11.  Mean t o t a l t u r i o n numbers p e r s q u a r e m e t e r for f i v e elevations ( i n r e l a t i o n to Chart Datum), A p r i l 1976 t o J a n u a r y 1977  Page  62,63  X  L I S T OF  APPENDICES  Appendix 1.  2.  3.  4.  5.  6.  7.  8.  9.  10.  11.  12.  Page  S e c c h i d e p t h and s u r f a c e and subsurface (1.5 m) s a l i n i t y and t e m p e r a t u r e m e a s u r e ments. M a r c h 1976 t o J a n u a r y 1977  92  D i u r n a l s u r f a c e and s u b s u r f a c e (1.5 m) s a l i n i t y ( p a r t s p e r thousand) measurements. May 2, J u l y 2 8 and O c t o b e r 4, 19 76. J a n u a r y 18, 1977  93  D i u r n a l a i r , s u r f a c e and s u b s u r f a c e (1.5 m) t e m p e r a t u r e (°C) m e a s u r e m e n t s . May 2, J u l y 28 and O c t o b e r 4, 1976. J a n u a r y 18, 1977 ....  94  D i u r n a l S e c c h i d e p t h and p h o t o s y n t h e t i c a l l y a c t i v e r a d i a t i o n (PAR) m e a s u r e m e n t s . May 2, J u l y 28 and O c t o b e r 4, 19 76. J a n u a r y 18, 1977  95  Net o s c i l l a t i o n s o f sediment s u r f a c e l e v e l s measurements and s t a t i s t i c s . J u n e 19 76 t o J a n u a r y 1977  96  S t a t i s t i c s of standing crop information ( o r g a n i c dry weight per quadrat) used f o r optimum q u a d r a t s i z e d e t e r m i n a t i o n  97  O r g a n i c d r y w e i g h t i n grams p e r s q u a r e m e t e r f o r f i v e e l e v a t i o n s ( C h a r t Datum). April 1976 t o J a n u a r y 1977  98  A n a l y s i s o f v a r i a n c e summary t a b l e f o r mean l e a f standing crop (organic dry weight i n grams p e r 0.25 s q u a r e m e t e r q u a d r a t )  99  D e n s i t y i n t u r i o n s per square meter f o r f i v e e l e v a t i o n s ( C h a r t Datum). A p r i l 19 76 t o J a n u a r y 1977  100  A n a l y s i s o f v a r i a n c e summary t a b l e f o r mean t u r i o n d e n s i t y ( t u r i o n s p e r 0.25 s q u a r e m e t e r quadrat)  101  Reproductive t u r i o n density meter) f o r f i v e e l e v a t i o n s . 1976  102  (per square June t o A u g u s t ,  A n a l y s i s o f v a r i a n c e summary f o r s l o p e s o f t h e r e g r e s s i o n s o f t u r i o n numbers on o r g a n i c d r y w e i g h t f o r f i v e e l e v a t i o n s ( C h a r t Datum)  103  xi Appendix 13.  Mean b i o m a s s o f i n t e r t i d a l (0.8 m) e e l g r a s s i n grams p e r s q u a r e m e t e r ( o r g a n i c d r y w e i g h t ) . A p r i l 1976 t o J a n u a r y 1977  Page  104  xii ACKNOWLEDGEMENTS  F i n a n c i a l a s s i s t a n c e f o r t h i s study was p r o v i d e d by the B r i t i s h Columbia Hydro and Power A u t h o r i t y . e s p e c i a l l y indebted  I am  t o Mr. R. Dundas and Dr. R. Ferguson o f  the Environmental Group o f t h i s agency. r e c e i v e d from t h i s agency and these  The a s s i s t a n c e  individuals i s gratefully  acknowledged. My committee members, Dr. R. E. Foreman, Dr. P. G. H a r r i s o n and Dr. C. D. L e v i n g s , p r o v i d e d encouragement, advice and c o n s t r u c t i v e c r i t i c i s m d u r i n g the study. a l s o indebted  I am  t o my committee chairman, Dr. Runeckles.  I am s i n c e r e l y g r a t e f u l t o my f e l l o w  students,  Herb K l a s s e n , Ed Medley and Dave Swinbanks, f o r t h e i r f i e l d assistance. Rapatz, Regional  valuable  T i d a l i n f o r m a t i o n was p r o v i d e d by Mr. W. J . Tide Superintendent.  Mr. B i l l Tupper o f the  B r i t i s h Columbia I n s t i t u t e o f Technology gave valued t i o n on a e r i a l photography.  Dr. J . Luternauer  informa-  o f the  G e o l o g i c a l Survey o f Canada was most h e l p f u l i n p r o v i d i n g i n f o r m a t i o n concerning River foreshore.  the g e o l o g i c a l s e t t i n g o f the F r a s e r  I a p p r e c i a t e the a s s i s t a n c e o f these  individuals. I am p a r t i c u l a r l y indebted  t o my s u p e r v i s o r ,  P r o f e s s o r V. C. B r i n k , f o r h i s h e l p , p a t i e n c e and guidance throughout the course  o f t h i s work.  F i n a l l y , I am deeply moved by the support, and extreme p a t i e n c e r e c e i v e d from my w i f e , c o n f i d a n t e and c o l l e a g u e , Anne.  friend,  assistance  1.  INTRODUCTION  1.1.  Purpose o f t h e Study Most o f t h e B r i t i s h  precipitous;  the shallow  successful  establishment  rare  our coast.  along  Fraser River Delta seagrass  Zostera  Columbia c o a s t l i n e i s t y p i c a l l y  protected  areas  o f seagrass  marina  s a n d and mud f l a t s  l a r g e meadows o f t h e n o r t h  L. ( e e l g r a s s ) .  A n g i o s p e r m , i s a member o f t h e f a m i l y subfamily (den  Zosteroideae,  Hartog  ebrates,  19 7 0 ) .  fish  tidal  genus Z o s t e r a ,  flats  forresidential,  p u r p o s e s have b e e n i n c r e a s i n g . of e e l g r a s s h a b i t a t , these mental e f f e c t s alteration increased shore.  and  i s well-documented i n  proposals  industrial  and r e c r e a t i o n a l  eelgrass habitat  resource  of eelgrass  i s to provide  along  the fore-  of various  of the Fraser  i s r e q u i r e d on t h e h a b i t a t  study  through  and water q u a l i t y , and  and r e c r e a t i o n a l t r a f f i c  growth c h a r a c t e r i s t i c s  t o develop  detri-  To m i n i m i z e t h e d e l e t e r i o u s e f f e c t s  purpose o f t h i s  ( P h i l l i p s 1975,  d e v e l o p m e n t s may a l s o have  of current patterns  information  to invert-  losses  on t h e r e m a i n i n g  industrial  Zostera  In a d d i t i o n t o d i r e c t  d e v e l o p m e n t s on t h e e e l g r a s s Delta,  years,  temperate  a marine  and subgenus  and European l i t e r a t u r e In recent  of the  Potamogetonaceae,  The i m p o r t a n c e o f e e l g r a s s  Thayer e t a l 1975). the  Z. marina,  and w a t e r f o w l p o p u l a t i o n s  the North American  f o r the  meadows a r e r e l a t i v e l y  The e x t e n s i v e  support  necessary  River  requirements  i n the area.  some o f t h a t  The  information.  2  1.2.  Previous Research In  a comprehensive  study of the seasonal growth of  some seventy taxa of b e n t h i c marine p l a n t s i n Great Pond e s t u a r y , Massachusetts, Conover ( 1 9 58) found t h a t the r e l a t i o n s of environmental f a c t o r s t o the growth and b u t i o n of Z. marina  were not w e l l - d e f i n e d .  distri-  High s t a n d i n g crop  values of e e l g r a s s were found i n those s e c t i o n s of the e s t u a r y where s a l i n i t i e s ranged from 1 2 to 3 2 % o , lower values were o b t a i n e d i n areas where the s a l i n i t y range was  not p r e s e n t i n areas having l e s s than l % o  and e e l g r a s s was salinity.  1 to 3 0 % o ,  Standing crop maxima and minima f o r e e l g r a s s were  a s s o c i a t e d w i t h the annual maxima and minima of i n s o l a t i o n and water temperature. f a c t o r s , temperature  Conover suggests t h a t these  two  and l i g h t , p l a y l e a d i n g r o l e s i n the  seasonal growth o f e e l g r a s s i n Great Pond. S e t c h e l l ' s scheme developmental  ( 1 9 2 9 )  d e s c r i b i n g v a r i o u s growth,  and p h e n o l o g i c a l a c t i v i t i e s of e e l g r a s s based  on 5°C water temperature  increments has not been borne out i n  the r e c e n t works of Burkholder and Doheny and P h i l l i p s  (  1  9  7  2  )  ( 1 9 6  ( 1 9 7 4 )  ( 1 9 6 9 )  .  Based on i n f o r m a t i o n from t r a n s p l a n t Phillips  8), McRoy  experiments,  suggests t h a t the lower depth l i m i t of e e l -  grass growth i n Puget Sound, Washington i s determined by availability.  C o n t r o l l e d f i e l d experiments  C a l i f o r n i a by Backman and B a r i l o t t i  ( 1 9 7 6 )  i n southern confirmed t h a t  e e l g r a s s t u r i o n d e n s i t y i s a f u n c t i o n of i r r a d i a n c e by the p l a n t s .  light  received  A t u r i o n i s a l e a f y branch a r i s i n g from the  3 horizontal  rhizome. In Chesapeake  (19 73)  found that  of eelgrass fractions  Bay on t h e A t l a n t i c  t h e sediments  a r e more p o o r l y  Coast, Orth  a s s o c i a t e d w i t h dense  sorted  and c o n t a i n h i g h e r f i n e  than t h e sediments from areas o f l e s s  g r a s s growth.  Similarly,  Stout  (19 76)  dense  describes  s h i p between t h e o c c u r r e n c e o f v e r y f i n e - g r a i n e d silts  and t h e presence o f e e l g r a s s beds.  characteristics  stands  These  a  eel-  relation-  s a n d s and sediment  a r e a t t r i b u t e d by b o t h a u t h o r s t o a t r a p p i n g  a c t i o n by e e l g r a s s .  E e l g r a s s has n o t been  observed  growing  on s a n d i n p r e v i o u s s t u d i e s o f e e l g r a s s p o p u l a t i o n s on t h e Pacific  Coast. Phillips  habitat  factors  Washington  (1972) and S t o u t  associated with eelgrass  and N e t a r t s Bay, Oregon Taxonomic c l a s s i f i c a t i o n  genus Zostera  has been,  measurement i n f o r m a t i o n plants.  (1976) d e s c r i b e t h e  to a large  o f t h e members o f t h e e x t e n t , b a s e d on  marina  A t l a n t i c Coast o f North America  Sound,  respectively.  and t h e v e r t i c a l  Two f o r m s o f Zostera  f o r Puget  leaf  distribution  of the  a r e r e c o g n i z e d on t h e  (Setchell  1920, H a r r i s o n a n d  Mann 1975) a n d A l a s k a (McRoy 1972) .  A short, narrow-leafed  form i n h a b i t s  and u p p e r  the shallow i n t e r t i d a l  of these areas. deeper s u b t i d a l  The t a l l e r ,  water  Columbia  forms  occurred.  zones  form i s found i n t h e  waters.  Along the P a c i f i c British  broad-leafed  subtidal  Coast o f North America,  to California,  t h e s h a l l o w - w a t e r and d e e p e r -  are present but a size The n a r r o w ,  short  from  shift  a p p e a r s t o have  f o r m o f t h e i n t e r t i d a l and  4 shallow subtidal broad-leafed  reaches of t h i s  form o f t h e A t l a n t i c C o a s t  Alaska . (Phillips central  Pacific  latifolia typical  1972).  for  The t a l l ,  Coast, often  (Scagel  1961) and  w i d e - l e a f e d form o f t h e  referred  t o as Z. marina  var.  M o r o n g , h a s much w i d e r a n d l o n g e r l e a v e s t h a n t h e  form  (Setchell  fusion exists within larger  area corresponds t o the t a l l ,  form  1927).  geographical areas; leaf  Z. marina  f. l a t i f o l i a  southern B r i t i s h  Columbia  s h o r t , n a r r o w - l e a f e d form d e s c r i b e d by S c a g e l  C o n s i d e r a b l e taxonomic  con-  length of the  d e s c r i b e d b y Outram  i s t h e same as t h a t  Z. marina  v a r . typioa  (1961) f o r B r i t i s h  (1957)  f o r the {marina)  Columbia  coastal  waters. Setchell temperature latifolia for  (1927) f e l t  that  resulted,in  the f u l l  a l o n g e r growing  v e g e t a t i v e development  of the p l a n t .  Setchell  the A t l a n t i c Coast described a n d makes no m e n t i o n  the A t l a n t i c  (19 70) upper  felt size  form  limit  an u n d e r d e v e l o p e d  (var.  Coast.  (Setchell form  Den H a r t o g  t h e r e was c o n s i d e r a b l e o v e r l a p o f t h e of the t y p i c a l  f o r m and t h e l o w e r  var. l a t i f o l i a  and r e g a r d e d t h e two forms  of  t h e t a x o n , Z.  marina.  as  Humboldt Bay, n o r t h e r n C a l i f o r n i a  f o u n d an i n c r e a s e  angustifolia)  o f the presence o f the t y p i c a l  of  In  allowed The t y p i c a l  i n an e a r l i e r work  Coast along the P a c i f i c  that  var.  (1927) d i d n o t a t t e m p t t o  a c c o u n t f o r t h e s h o r t , narrow growth  of  season which  C o a s t was t h u s m e r e l y  form o f v a r . l a t i f o l i a .  19 20)  i n water  o b s e r v e d f o r a r e a s i n h a b i t e d by Z. marina  form o f t h e A t l a n t i c  of  the slow r i s e  i n mean t u r i o n  size  limit  phenotypes  Keller  length of i n t e r t i d a l  (196 3) Z.  marina  5 with  increased  of t h i s and  depth but  failed  relationship in this  H a r r i s 1966) .  dimensions with  A  and  across  two  Phillips  mean low plane  o f d e p t h on water  tidal  (MLW), t h e  mean l o w e r low  of the Coast  two  low  zones  (intertidal  variation butable  water  (MLLW), t h e  distinctions  An  zones  Z.  marina  by  York but  leaf  seagrasses  Pacific  that  validity information  length  (Strawn  depth  Doheny  the  attri-  the  in leaf  and  lower  f o r the  l e a f measurement  Burkholder i s not  the  discounted  the  Coast  z o n e s was  l e n g t h and  States,  waters, i s  plane  tidal  increase  f o r other  inverse r e l a t i o n s h i p of  L o n g I s l a n d , New  subtidal)  United  average of  and  b a s e d on  An  i s reported  In the  (1972) c o n c l u d e d  plasticity  been r e p o r t e d  and  the A t l a n t i c  i s the  Phillips  f o r P u g e t Sound e e l g r a s s . d e p t h has  Datum on  dimensions across  to phenotypic  in  broad t i d a l  a v e r a g e o f a l l low  w a t e r s e a c h day,  in leaf  of v a r i e t a l  dimensions.  Chart  (Chapman 1 9 6 0 ) .  (19 72)  leaf  b e l o w LLLW) t o i n v e s t i g a t e t h e  leaf  which r e p r e s e n t s  (Keller  used r e c i p r o c a l t u r i o n  l e a f measurements o f t u r i o n s f r o m t h r e e  influence  the  paper  r e l a t i o n s h i p of increased  He  (MLLW, MLLW t o LLLW, and  and  the s i g n i f i c a n c e  in a later  o b s e r v e d by  P u g e t Sound, W a s h i n g t o n . transplants  and  similar  d e p t h was  t o remark on  with 1961).  for (1968) f o r  s u b s t a n t i a t e d elsewhere  in  literature. Tidal  other  characteristics  reproductive crop,  elevation exerts  and  b i o m a s s and  d e n s i t y on  the  considerable  influence  of eelgrass populations.  vegetative phenology.  turion density, Studies  These  leaf  of eelgrass  P a c i f i c Coast of North America  on  include  standing turion  report  6 conflicting  results.  Keller  the h i g h e s t e l e v a t i o n  and H a r r i s  they considered  (1966)  (0.3 m e t e r s  MLLW) h a d t h e l o w e s t t u r i o n d e n s i t y ; more however, t h e i r above  data reveal  that  (Phillips  reported  decreased This  e e l g r a s s d e n s i t y was l e s s Reproductive t u r i o n  than i n t e r t i d a l  zone o f P u g e t Sound  f r o m MLLW  (McRoy 19 72) where  d e n s i t y was a l s o  turion  subtidal density.  greater i n the interConversely,  Stout  (1976), w o r k i n g i n N e t a r t s Bay, Oregon,  f o u n d t h a t deep  water  eelgrass  and r e p r o d u c t i v e  turion  (Phillips  relation-  Washington  19 72) where t u r i o n d e n s i t y d e c r e a s e d  w i t h g r e a t e r depth and A l a s k a  tidal  (MLLW).  f r o m P u g e t Sound,  above  significantly,  turion density  and b e l o w mean l o w e r low w a t e r  s h i p was a l s o  found t h a t  had s i g n i f i c a n t l y  higher  1972).  total  d e n s i t i e s than shallow water e e l g r a s s .  s h a l l o w and deep w a t e r e e l g r a s s to provide  as d i s t i n c t  any e l e v a t i o n a l o r m o r p h o l o g i c a l  She c o n s i d e r e d  groups b u t f a i l e d information for  t h e two t y p e s . I n t h e same s t u d y S t o u t  f o u n d t h a t t h e deep  water  e e l g r a s s h a d a much h i g h e r b i o m a s s p e r s q u a r e m e t e r t h a n t h e shallow water e e l g r a s s . those o f other P a c i f i c reported  that  These r e s u l t s Coast eelgrass  intertidal  do n o t a g r e e w i t h studies.  biomass always exceeded  b i o m a s s a t h i s Bush P o i n t , W a s h i n g t o n  study  site  P o i n t , Washington  s u b t i d a l biomass o n l y exceeded  biomass  t o September  tidal  from J u l y  leaf  creased  standing  when a l a r g e  crop occurred.  from t h e upper l i m i t  Phillips  (1972)  subtidal and a t A l k i intertidal  increase  i n sub-  E e l g r a s s biomass i n -  of eelgrass  growth  (0.5 m e t e r s  above MLLW) t o -0.5 m e t e r s a n d d e c r e a s e d g r a d u a l l y  thereafter  7 to i t s lower l i m i t (Backman and  -2.75  Barilotti  (1966) d e s c r i b e tidal  of  eelgrass  an  1976).  increase  m e t e r s and  vation  meters) they  The z o n e s , on leaf  and  density  rhizome standing  marina  0.3  tidal  meters  e v e n t s as  crops,  lowest  ele-  seasonal  Phillips  (1972).  to the  of  biomass,  influenced  f a c t o r s w h i c h change w i t h d e p t h . as  turion  ecological studies  are  true  tidal  changes i n  c e r t a i n morphological,  literature  broad  t o t a l b i o m a s s and  review of previous  which e x i s t s i n the  inter-  above  e l e v a t i o n , across  c h a r a c t e r i s t i c s of eelgrass  environmental  crop of  decrease a t the  f o r P u g e t Sound by  indicates that  population  of  Harris  studied.  such p h e n o l o g i c a l  This Z.  i n l e a f standing  a slight  influence of  i s described  California  S i m i l a r l y , K e l l e r and  from i t s upper l i m i t  MLLW t o -0.3 (-0.5  meters i n southern  The  by confusion  nature of  change i n t h e s e c h a r a c t e r i s t i c s w i t h d e p t h c a n  be  and  the  attributed  to: 1.  studies  conducted over only  of eelgrass 2.  studies only  one  describing or  Phillips 3.  studies tidal  ( K e l l e r 1963,  two  K e l l e r and  i n f l u e n c e of  parameters  the  Harris tidal  ( B u r k h o l d e r and  tidal  range  1966)  elevation  on  Doheny 196 8,  1974) comparing e e l g r a s s  zones, e.g.  s h a l l o w and  deep  Liebig^s d e p e n d e n t on  the  a portion of  the  been g e n e r a l l y  c h a r a c t e r i s t i c s across  intertidal (Stout  law  of  and  subtidal  (McRoy  broad 1972),  1976).  the  minimum, t h a t p l a n t  nutrient present  expanded t o the  yield  i n minimum q u a n t i t y ,  is has  broader e c o l o g i c a l concept  of  8 limiting  factors, i . e . , that  or exceeds the l i m i t s be  a limiting  upper l i m i t  desiccation  tidal The  growth i s d e t e r m i n e d  o f the p l a n t which, i n t u r n , composition  f a c t o r c o n t r o l l i n g the lower l i m i t (Phillips  turbid coastal  fluences  the  (den H a r t o g  of eelgrass  1976).  waters, water c l a r i t y i n -  environment o f e e l g r a s s  ( B u r k h o l d e r and  I t i s reasonable to expect that  limiting  previously  factors, light  described  19 7 0 ) .  i s light  and, c o n s e q u e n t l y , t h e p h o t o s y n t h e t i c  the plant.  different  i s a function of  1972, Backman and B a r i l o t t i  and e s t u a r i n e  the l i g h t  Doheny 196 8) of  o f an o r g a n i s m i s s a i d t o  o f Z. marina  e x p o s u r e and s u b s t r a t e  availability In  of tolerance  approaches  factor.  The by  the c o n d i t i o n which  activity  t h e s e two v e r y  and d e s i c c a t i o n ,  influence  c h a r a c t e r i s t i c s of eelgrass i n  d i f f e r e n t ways as i t s u p p e r and l o w e r d i s t r i b u t i o n a l l i m i t s are  approached. A  tive  study o f s e a s o n a l changes i n t o t a l  turion d e n s i t i e s , l e a f standing  dimensions,  tidal  elevation  of  eelgrass  a means o f d e t e r m i n i n g t h e i n f l u e n c e o f on e e l g r a s s  would a l s o p r o v i d e factors  c r o p and l e a f and r h i z o m e  from t h e upper t o t h e lower l i m i t s  growth, p r o v i d e s  and r e p r o d u c -  influence  near i t s t o l e r a n c e  characteristics.  Such a s t u d y  i n s i g h t i n t o t h e ways i n w h i c h the vegetative limits.  limiting  characteristics of  eelgrass  1.3.  Objectives Considering  previous  of the the  Study-  purpose o f the  autecological research  on  study,  and  e e l g r a s s , the  following  o b j e c t i v e s were e s t a b l i s h e d : 1.  To  assess  the  seasonal  and  d i u r n a l changes i n  m e n t a l f a c t o r s o f e e l g r a s s h a b i t a t on  environ-  southern  Roberts  Bank. 2.  To  determine the  upper to the eelgrass  growing 3.  To  lower l i m i t s  standing  densities,  influence of t i d a l  and  crop,  leaf  and  e l e v a t i o n , from  of eelgrass d i s t r i b u t i o n ,  reproductive  and  total  the on  turion  rhizome dimensions d u r i n g  the  season.  d e s c r i b e biomass changes o f e e l g r a s s  during  a  growing  season. 4.  To  collate  the  above i n f o r m a t i o n  h a b i t a t r e q u i r e m e n t s and grass  on  southern  to b e t t e r understand  growth c h a r a c t e r i s t i c s  R o b e r t s Bank.  of  the  eel-  10  2.  THE  STUDY AREA  The  study  area, shown i n F i g u r e 1, i s  20 k i l o m e t e r s south o f the C i t y o f Vancouverical  l o c a t i o n o f the study  s i t e , adjacent  the Tsawwassen F e r r y Terminal l a t i t u d e , 123° southern  07' W.  approximately  The  to and  south  Causeway, i s 49° 00'  longitude.  geographof  N.  Roberts Bank a d j o i n s  the  S t r a i t o f Georgia between the main d i s t r i b u t a r y  channel of the F r a s e r R i v e r and Boundary.  The  study  the Canada-USA I n t e r n a t i o n a l  s i t e i s approximately  south of the mouth of the south arm F i e l d reconnaissance and topographic  and  6 kilometers  due  of the F r a s e r R i v e r .  i n f o r m a t i o n from a e r i a l photographs  maps were used i n the s e l e c t i o n o f the  s i t e , as shown i n F i g u r e 2.  A uniform  study  cover of e e l g r a s s from  the upper to the lower e l e v a t i o n a l l i m i t s of e e l g r a s s growth, and  a c c e s s i b i l i t y , both on f o o t and by boat, were major con-  s i d e r a t i o n s i n s e l e c t i n g the study The  site.  F r a s e r R i v e r D e l t a i s composed of r e c e n t  sedi-  ments s e v e r a l hundreds of f e e t t h i c k over P l e i s t o c e n e sediments  (Mathews and Shepard 1962).  An e x c e l l e n t summary  of the geology of the F r a s e r R i v e r D e l t a i s given Luternauer  (Hoos and Packman 19 74) .  by  K e l l e r h a l s and Murray  (1969) d e s c r i b e the sedimentary c h a r a c t e r i s t i c s of the f l a t s covered  by e e l g r a s s i n Boundary  Previous  tidal  Bay.  v e g e t a t i o n s t u d i e s o f the F r a s e r R i v e r  e s t u a r y have been l a r g e l y d e s c r i p t i v e and ignored the submerged v a s c u l a r p l a n t s . c r i p t i o n s are p r o v i d e d by Forbes  a l l but two  have  General marsh des-  (1972a,b), McLaren  (1972)  11  Fig.  1.  A e r i a l photo mosaic o f the F r a s e r R i v e r showing l o c a t i o n o f the study a r e a .  Delta  13  Fig.  2.  Diagram o f the study locations.  site  showing  transect  14  CANADA U.S.A.''  15  and H i l l a b y and B a r r e t t (1976).  Forbes (1972c) p r o v i d e s  rough maps and e s t i m a t e s o f e e l g r a s s coverage f o r the F r a s e r R i v e r f o r e s h o r e and Boundary Bay.  H i s t o r i c a l changes i n the  R o b e r t s Bank e e l g r a s s bed and h a b i t a t and p o p u l a t i o n  char-  a c t e r i s t i c s o f Roberts Bank e e l g r a s s are d e s c r i b e d i n an environmental  impact assessment o f Roberts Bank p o r t  e x p a n s i o n prepared  f o r the N a t i o n a l Harbours B o a r d , P o r t o f  Vancouver (1977) by Beak C o n s u l t a n t s L t d .  Yield  estimates  o f the major emergent marsh p l a n t s are g i v e n by Yamanaka (19 75) but i n f o r m a t i o n on the submergent v e g e t a t i o n i s l a c k i n g . S i m i l a r l y , Burgess (1970) d e s c r i b e s the importance o f v a r i o u s emergent s p e c i e s t o s e v e r a l s p e c i e s o f d a b b l i n g ducks on the F r a s e r f o r e s h o r e marshes.  Burgess r e p o r t s t h a t the  p h y s i c a l environment o f the t i d a l marshes e x e r t s s t r o n g i n f l u e n c e s on the c o m p o s i t i o n  and d i s t r i b u t i o n o f the  vegetation. The  e s t u a r i n e w a t e r s a d j a c e n t t o the F r a s e r R i v e r  f o r e s h o r e are h i g h l y s t r a t i f i e d  (Hoos and Packman 19 74) , a  f a c t o r w h i c h i s s t r o n g l y i n f l u e n c e d by wind and t i d e - d r i v e n currents. Georgia  T i d e s i n the s o u t h e r n  p o r t i o n o f the S t r a i t o f  are of the mixed, m a i n l y d i u r n a l t y p e .  s i t e the mean t i d a l range i s 3.05 the range averages 4.69  meters.  A t the  study  meters; f o r l a r g e t i d e s Mean water l e v e l , the average  o f a l l h o u r l y o b s e r v a t i o n s , i s 2.96  meters.  During  the  summer, extreme lower low w a t e r a s s o c i a t e d w i t h 'the s p r i n g t i d e s o c c u r s near midday; i n the w i n t e r , near m i d n i g h t . times are r e v e r s e d f o r extreme h i g h e r h i g h w a t e r H y d r o g r a p h i c S e r v i c e 19 76).  The  (Canadian  In Canada, C h a r t Datum (CD)  is  16 the plane  of  lowest  normal t i d e s  mean l o w e r low w a t e r 1 meter above  (MLLW).  At  The  foreshore  proximity  rapidly  have i n c r e a s e d  of the  developments are  and  of the  e n c r o a c h m e n t on  Harris  and  Taylor  industrial  of the  taken the  way  In  discussed  on  the  proposals  across  multi-fold  vary  the  the  sand  from s l i g h t  to  and  factors  and  adjacent lower  Dorcey  (1976).  d e v e l o p m e n t s have The  facility  R o b e r t s Bank. cables  form of the  resource  of  have b e e n  cause-  laid  Current  R o b e r t s Bank i n c l u d e port  a  facility.  port expansion,  southern  considerable.  and  in  In a d d i t i o n ,  f l a t s o f R o b e r t s Bank. southern  urban  reaches  Causeway were c o n s t r u c t e d port  in  proposed  (1974)  of the  a t l e n g t h by  telecommunication  eelgrass  large  causeway c o n s t r u c t i o n .  southern  ultimate  years.  progressive  i n f l u e n c e o f the  R o b e r t s Bank r e c e n t  and  Fraser  increasing  Packman  the water q u a l i t y  f u r t h e r develop  the  the  t o the  expansion o f the Westshore Terminal  D e p e n d i n g on e f f e c t s on  along  S e v e r a l of the  the Westshore Terminal  intertidal to  s i t e MLLW i s  a l l important  lands.  The  f o r m o f p o r t and  1970  and  i n Hoos and  (1973).  areas  s e v e r a l power and  will  are  foreshore  southern  were b u i l t  across  below  greatly i n recent  populace,  area  Tsawwassen F e r r y T e r m i n a l 1960.  f o r areas  Fraser River i s discussed On  study  o f Vancouver, the  demands o f t h e  industrialization the  the  Fraser River Estuary  growing m e t r o p o l i s  recreational  i s therefore  CD.  Development p r o p o s a l s River  and  the  R o b e r t s Bank  17 3.  ENVIRONMENTAL FACTORS IN RELATION TO  3.1.  M a t e r i a l s and Seasonal  Methods  changes i n s a l i n i t y ,  c l a r i t y were d e t e r m i n e d from A p r i l 1977.  to August  and  the study  19 76  and  monthly t h e r e a f t e r  l i g h t were m o n i t o r e d  taken and,  just  o f the  study  seaward o f the  a t u r e were m e a s u r e d in  b e l o w s u r f a c e , w i t h a YSI Conductivity-Temperature electrical from  conductivity  summer,  boundary o f t h e e e l g r a s s bed  + 0 . 1 ° C a t -2°C  a t the  meter.  t h e s e measurements.  and  manufacturer and  and  1.5  meters  measures  computes lists  +0.7%o  temper-  Salinity-  This instrument  f o r temperature  program,  Salinity  s u r f a c e and  temperature  The  fall  A l l measurements were  M o d e l 14 86 p o r t a b l e  and  January  Figure 3 i s a  14.0 0 h o u r s .  situ,  2 weeks  water  w i t h the e x c e p t i o n o f the d i u r n a l m o n i t o r i n g  were made between 10.0 0 and  at  spring,  area.  site.  lower  water  four occasions during  p e r i o d , corresponding to the  profile  and  to  temperature,  on  and w i n t e r c o n d i t i o n s i n t h e s t u d y schematic  temperature  from measurements made e v e r y  D i u r n a l changes i n s a l i n i t y ,  clarity  EELGRASS HABITAT  salinity  i t s accuracy  a t 20%  o  for  sali-  nity . A  30  cm  (diameter)  the  transmission of v i s i b l e  The  d i s c was  slowly raised  lowered until  w a t e r c l a r i t y , was readings.  into  S e c c h i d i s c was light  through  the water u n t i l  i t reappeared.  used  the water  column.  i t disappeared  Secchi depth,  r e c o r d e d as t h e a v e r a g e  t o measure  a measure o f  of these  D i u r n a l changes i n p h o t o s y n t h e t i c a l l y  and  two  active  18  Fig.  3.  Schematic p r o f i l e o f the study s i t e showing t r a n s e c t e l e v a t i o n s i n r e l a t i o n t o C h a r t Datum.  20 radiation  (PAR)  were m e a s u r e d w i t h  a LI-COR M o d e l L I - 1 8 5  Quantum/Radiometer/Photometer equipped w i t h quantum  upper l i m i t  using predicted t i d a l Tsawwassen c o n t a i n e d  of eelgrass  information i n the  Canadian Hydrographic  lished and  just within  the  other  the  19 76  e e l g r a s s g r o w t h was  f o r the Tide  Service.  and  determined  Secondary P o r t  of  Current  of  Transect  upper boundary o f the  a survey  s t a d i a rod.  determined a t the  o f t r a n s e c t A was  later  confirmed  readings  from the  from the  Institute  Service,  E n v i r o n m e n t Canada, V i c t o r i a .  Tsawwassen T i d a l  Tables  A was  estab-  eelgrass  The  bed  lower l i m i t  same t i m e . using  The  hourly  tidal obtained  F i s h e r i e s and This  Marine  information  exposure of t r a n s e c t s A  and  concerning  t h e r e was  tidal  a need f o r v e r y  accurate  elevations, transects A  f r o m B e n c h Mark "Geod. No.  B  and  information  B were  surveyed  66-C-045" l o c a t e d i n t h e w a l l o f  H u l l M a i n t e n a n c e B u i l d i n g , Tsawwassen F e r r y T e r m i n a l , 12,  1977.  used  A K e u f f e l and  f o r the surveyed  polation  survey.  al  Esser  of hourly  (1974) was  a l i d a d e and  T h e r e was  e l e v a t i o n s and tide  A technique et  was  1976. As  the  of  eleva-  S t a t i o n f o r 19 76  o f Ocean S c i e n c e s ,  a l s o used to determine t i d a l for  g r o w t h was  f o u r t r a n s e c t s were l o c a t e d a t 0.5^ m e t e r  depth i n t e r v a l s with  tion  underwater  sensor. The  the  an  plane  good a g r e e m e n t  those  determined  on  March  t a b l e were  (+3  from  cm)  between  inter-  heights.  similar  to that described  the  by  used t o monitor sediment s u r f a c e  Ranwell level  o s c i l l a t i o n s w i t h i n the e e l g r a s s bed. diameter  and  Twenty 2.5  cm  30  cm  l o n g wooden s t a k e s were p u s h e d i n t o  substrate u n t i l  10  cm  t h e e e l g r a s s bed grass growth. at  intervals  from  The from  a t 10 m e t e r i n t e r v a l s  the upper t o the  July  1976  tubes  to January  10  cm  long  t o remove s e d i m e n t c o r e s  the  stakes  i n October  was  subjected to various physical  Carbonate carbon  was  19 76,  matter  ignition carbon  c o n t e n t by  mended by US  Standard  perform dry  Trask  Sieves  (4.0  Dry  size  3.2.  eel-  measured  4  adjacent  to  of each  chemical  cm)  core  determinations.  f o l l o w i n g the g r a v i m e t r i c  loss  Black  i n weight  converted  a f a c t o r o f 1.8  cm  analysis.  (1965).  on  to organic as  recom-  a set of  nested  o p e n i n g s ) was  s e d i m e n t were p l a c e d i n t h e t o p s h a k e n on  areas  sieving with  t o 0.1  of  diameter  t h e u p p e r 5 cm  and was  d i v i s i o n with  (19 3 9 ) .  (inside  and  across  1977. -  from  f o u n d by  (Wood 1975)  the p a r t i c l e  s i e v e s was  limits  d i o x i d e d e s c r i b e d by  c o n t e n t was  a t 550°C  and  determined  method f o r l o s s o f c a r b o n Organic  lower  l e n g t h o f s t a k e p r o t r u d i n g was  Plexiglas were u s e d  protruded  the  used  Approximately s i e v e and  a ROTAP m a c h i n e f o r 2  the  40  to g  of  set of  minutes.  Habitat Factors 3.2.1.  Salinity  3.2.1.1. The g r e a t e r than  1.5  m  Seasonal salinity  surface s a l i n i t y  Changes  ( F i g u r e 4) was except  f o r one  consistently anomalous s e t  22  Fig.  4.  Surface and 1.5 m s a l i n i t i e s and temperatures a t the study s i t e and mean monthly a i r temperature a t Vancouver I n t e r n a t i o n a l A i r p o r t (Monthly Record, M e t e o r o l o g i c a l O b s e r v a t i o n s i n Canada, Atmospheric Environment, F i s h e r i e s and Environment Canada, A p r i l 1976 t o January 1977). Mean monthly a i r temperature p l o t t e d a t the midpoint o f each month.  23  A  1  M  I  j  I  j  I  A  I  S  I  MONTH  6  I  N  I  fj  I  J  I  \ \  A  I  M  I  J  I  J  I  A  I  S  MONTH  I  0  I  ti  I  fj  I  \  J  I  24 of  measurements i n m i d - w i n t e r .  differences early The  S u r f a c e and 1.5 m  salinity  a r e on t h e o r d e r o f 1 t o 2%o i n t h e s p r i n g and  summer, and i n c r e a s e two- t o t h r e e f o l d b y l a t e  pronounced  salinity  stratification  summer.  i s maintained  until  winter.  3.2.1.2. The  Diurnal  diurnal  Changes  salinity  measurements o f F i g u r e 5  reflect,  to a great extent, the pertinent  seasonal  salinity  January in  changes.  18, 1977 show t h a t  t h e w i n t e r and s p r i n g .  nity  O b s e r v a t i o n s o f May 2, 19 76 and t h e w a t e r column was w e l l On.July  a t 1.5 m e t e r s was m a i n t a i n e d  cycles.  By O c t o b e r  subsurface waters  features of the  the s a l i n i t y  28, 19 76  mixed  the higher  a c r o s s two c o m p l e t e difference  was g r e a t e r t h a n  salitidal  o f s u r f a c e and  that observed  during the  summer.  3.2.2.  Temperature  3.2.2.1. Seasonal salinity  Seasonal  Changes  trends i n water temperature  i n that the thermal  stratification  apparent  summer d i s a p p e a r s d u r i n g t h e r e s t o f t h e y e a r The  s e a s o n a l i n c r e a s e and d e c r e a s e  curve  (Figure 4).  lower  than  fol-  f o r Vancouver  20 k i l o m e t e r s n o r t h , c l o s e l y  when t h e c u r v e s d i v e r g e and t h e mean m o n t h l y becomes i n c r e a s i n g l y  i n the  i n water temperature  lows t h e mean m o n t h l y a i r t e m p e r a t u r e International Airport,  resemble  air  until  fall  temperature  the sea temperature.  25  Fig.  5.  D i u r n a l s u r f a c e and J u l y 2 8 and O c t o b e r  1.5 m s a l i n i t i e s . 4, 19 76. January  May 2, 18, 19 77.  26  3.2.2.2. Figure and  subsurface  Diurnal  Changes  6 indicates that winter  and  spring  w a t e r t e m p e r a t u r e s were v e r y  constant  24-hour s a m p l i n g p e r i o d .  The  w a t e r column i s w e l l  during  the  summer t h e  air  these  seasons.  i s warmer t h a n t h a t o f t h e  t u r n , warmer t h a n t h e information  of the  o f the  a i r and  above t h e first  sun  can  surface  horizon,  subsurface,  The  also  3.2.3.  how  the  waters.  increased  As  the  and  rose  concomitant water  occurred.  Light  discharge  depth of waters a t the 3.2.3.2.  S e a s o n a l Changes obvious  i n v e r s e r e l a t i o n s h i p between  c y c l e of the study  site  Diurnal  Fraser River  (Figure  the  within  t h a n between s a m p l i n g  d i u r n a l monitoring  from the  and  the  Secchi  7).  Changes  d e p t h measurements and  during  discerned  sun  surpassed  then s u r f a c e water temperature; a  T h e r e i s an  Secchi  warming  temperature r e l a t i o n s h i p s  subsurface  a i r temperature  3.2.3.1.  seasonal  the  d i u r n a l temperature  illustrates  i n f l u e n c e the and  the  mixed  temperature of  i n s u r f a c e w a t e r t e m p e r a t u r e above s u b s u r f a c e  temperature  the  1976  over  s u r f a c e water which i s , i n  deeper water.  f o r O c t o b e r 4,  effect  rise  In  surface  sessions sessions.  information  as  light  data  show more No  gathered  trends  collected  variability could  (Appendix  4).  be  D i u r n a l a i r t e m p e r a t u r e s and s u r f a c e and 1.5 m water temperatures. May 2, J u l y 2 8 and O c t o b e r 1976. J a n u a r y 18, 1977.  4,  PACIFIC DAYLIGHT SAVING TIME  30  Fig.  7.  S e c c h i d e p t h (meters) a t t h e s t u d y s i t e and maximum d a i l y d i s c h a r g e ( t h o u s a n d s o f c u b i c m e t e r s p e r second) o f t h e F r a s e r R i v e r a t Hope, B.C. f o r e a c h month f r o m M a r c h 19 76 t o J a n u a r y 19 77.  32 A t m o s p h e r i c c o n d i t i o n s on for  d i u r n a l monitoring  was  overcast with  cleared high  clouds  October  4,  19 7 7 was  by  late  1976  was  cloudy  At g r o w t h was and  the  0.85  showers.  2,  1976  Morning  fog which  d u r i n g midday  afternoon  J u l y 28,  occurred  sunny w i t h a few  Tidal  the  of r a i n  May  noon, b r i g h t s u n s h i n e  with  3.2.4.  f o u r days s e l e c t e d  were h i g h l y v a r i a b l e .  periods  away b e f o r e  the  cloudy  sunny  Range and  study  site  periods  Percentage  Datum  -1.25  and  19 76. January  18,  periods.  Exposure  the upper l i m i t  meters Chart  l o w e r l i m i t was  on  and  of  eelgrass  (-0.15 m MLLW) ( F i g u r e  m CD  (-2.25 m MLLW);  the depth range f o r e e l g r a s s i n t h i s  area  is  2)  thus  approximately  2 meters.  P e r c e n t a g e e x p o s u r e s were c a l c u l a t e d f o r the' two  intertidal  transects  t h e Tsawwassen T i d a l study  site,  (A and  Two  tidal  methods were u s e d .  readings  The  a percentage of the  total  and  this  t o t a l was  expressed  number o f h o u r s i n 19 76.  This  e x p o s e d 1.00%  of the  and  s e c o n d , more  detailed  method e n t a i l e d  0.034% o f direct  1976.  interpolation  between a l l h o u r l y o b s e r v a t i o n s encompass t h e t r a n s e c t A had was  exposed  two  The  elevations.  of t i d a l  0.006% o f t h e y e a r .  did  T h i s method r e v e a l e d  The  0.9 36  first  year  heights  which i n c l u d e d but  a percentage exposure of  the  study  method i n d i c a t e d t h a t t r a n s e c t A was t r a n s e c t B,  at  first  t h e number o f h o u r s d u r i n g w h i c h t h e  e l e v a t i o n s were e x p o s e d i n 1976 as  from h o u r l y  S t a t i o n , l o c a t e d 1 k i l o m e t e r west o f  f o r 19 76.  method t o t a l l e d  B)  and  method  not  that  transect B over-  33 e s t i m a t e d the percentage ( t r a n s e c t B)  by more t h a n  3.2.5.  Figure oscillations  observed  p e r i o d was  fivefold.  S u r f a c e L e v e l Changes  at the study s i t e w i t h i n T h e r e was  The  overall  approximately  3.2.5.2.  2  bed  e r o s i o n observed  at the upper  Physical  and  which  are  more t h a n until  a t 10,  30 m e t e r s f r o m  study  1.  The  sample  taken  i s better  sorted  than  30 m e t e r s i n s i d e  the upper  sediment  a c r o s s the e e l g r a s s  t h e most p o o r l y s o r t e d o f a l l .  the upper  Sorting of  edge i n c r e a s e s w i t h  edge , samples depth  j u s t b e f o r e t h e l o w e r edge o f e e l g r a s s i s r e a c h e d .  moderate decrease distributional exhibits than  and  the  Characteristics  analysis of  a r e shown i n T a b l e  20  d u r i n g the  Chemical  edge o f t h e e e l g r a s s b e d  samples taken  sediments  cm.  a t 10 m e t e r i n t e r v a l s  at the study s i t e  of  boundaries  were t r a n s p o r t e d o u t o f  Results of a mechanical samples c o l l e c t e d  level  the  an a c c u m u l a t i o n  summer when s e d i m e n t s  e e l g r a s s bed.  elevation  8 depicts net substrate surface  o f the e e l g r a s s bed. late  o f the lower  Substrate  3.2.5.1.  until  exposure  the lower  limit  a similar  30 m e t e r s  i n degree  of sorting  of eelgrass.  limit.  Fines content  d e c l i n e w i t h depth  from the upper  occurs near  edge and  the  A  lower  (Figure  9)  at distances greater a slight  i n c r e a s e near  34  \  Fig.  8.  Net o s c i l l a t i o n s o f sediment s u r f a c e l e v e l s , J u l y 19 76 t o J a n u a r y 19 77. Mean + S t a n d a r d E r r o r .  35  -3.0  J  1  A  1  S  1  6  MONTH  1  N  1  D  1  J  36  Table 1.  P a r t i c l e s i z e composition o f sediments  P a r t i c l e Size (%) Distance (m) from Upper Edge of Eelgrass Growth 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 175 180  <0.10 mm  0.10 mm to .0.25 mm  33.86 32.21 21.06 22.29 33.87 26.78 23.87 21.75 18.82 18.68 14.74 11.57 11.89 10.31 9.61 8.05 8.47 14.17 15.34 12.23  57.70 44.03 47.67 43.47 54.22 62.26 66.48 69.22 71.96 69.77 74.25 77.61 76.68 76.98 80.47 79.95 78.80 73.26 70.52 72.36  0.25 mm to 0.50 mm  0.50 mm to 1.0 mm  5.11 21.22 27.66 29.55 6.96 5.47 4.58 4.85 5.30 4.75 6.94 7.66 8.02 8.29 6.88 8.61 9.12 7.73 8.90 12.17  1.44 1.23 1.78 2.42 1.72 1.08 .88 .66 .64 3.35 .86 6.26 .80 1.36 .65 1.27 1.06 1.34 1.70 1.54  > 1.0 mm 1.89 1.31 1.83 2.26 3.23 4.40 4.19 3.51 3.28 3.45 3.06 2.53 2.61 3.06 2.38 2.12 2.56 3.51 3.55 1.69  Fig.  9.  S e d i m e n t samples t a k e n a t 10-meter i n t e r v a l s f r o m the upper t o the lower l i m i t s o f e e l g r a s s growth: a. Percentage of f i n e s b. P e r c e n t a g e s o f o r g a n i c and c a r b o n a t e c a r b o n .  i  38  39 The  a p p a r e n t anomaly t h a t t h e  20  and  30 m e t e r s i n s i d e t h e  of  f i n e s than adjacent  sorted  i s explained  ( g r e a t e r t h a n 0.5  mm  u p p e r edge have l o w e r  s t a t i o n s and  by  the  high  the  carbon  ( F i g u r e 9,  upper l i m i t  noted  f o r both near the  percentages poorly  stations.  2)  decline with  growth.  and  distance  study  period grass  site,  i n d i c a t e only bed.  Excessive  important the  general  adjacent  eelgrass.  3.3.  by  study  studied,  site  as  across  the  study  the  eel-  a p p e a r t o be  i t i s protected  nearby P o i n t Roberts  marina  L.  which i n h a b i t s the  temperature  factors  occur  wave a c t i o n d i d n o t  where s u i t a b l e s u b s t r a t e  Bank a r e  currents  made d u r i n g  at  Causeway and,  an by  to  a  peninsula.  Discussion Zostera  seagrass  observations  Tsawwassen F e r r y T e r m i n a l  l e s s e r extent,  is  Currents  gentle  f a c t o r a t the  from  A moderate i n c r e a s e  A l t h o u g h c u r r e n t v e l o c i t i e s were n o t m e a s u r e d the  10,  l a r g e r sand f r a c t i o n s  l o w e r edge o f  Waves and  a r e more  of carbonate carbon  Table  of eelgrass  3.2.6.  yet  diameter) of these  Percentage contents organic  stations located  and  i s a euryhaline, shallow,  eurythermal  protected  i s a v a i l a b l e (Table  water motion c o n d i t i o n s of  c o a s t a l waters  3).  southern  c l o s e to the world-wide optima f o r these as  i n d i c a t e d by  light,  Table  substrate  and  3.  The  other  The  salinity,  Roberts  habitat  habitat factors  exposure, appear t o  account  Table 2.  Organic and carbonate carbon contents o f sediments  Content  Distance (m) from Upper Edge of Eelgrass Growth 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 175 180  Organic Carbon .96 1.12 .89 .83 1.19 1.03 .86 .97 .88 .84 .96 .64 .69 .62 .71 .62 .62 .79 .70 .59  (%)  Carbonate Carbon 2.45 3.03 2.14 1.90 2.68 2.42 1.96 1.86 2.02 2.09 1.81 1.54 1.93 1.90 1.53 1.26 1.48 1.98 2.17 1.81  4 1  Table 3 .  Comparisons of habitat factors affecting eelgrass growth (modified from Stout 1 9 7 6 , and Phillips 1 9 7 2 )  TEMPERATURE Range World-wide Optimum World-wide Southern Roberts Bank Range  0  -  1 0  4 0 . 5 ° C -  7 . 8  2 0 ° C -  1 7 . 5 ° C  SALINITY Range World-wide Optimum World-wide Southern Roberts Bank Range  Freshwater - 4 2 % o 1 0  -  1 3 . 8  3 0 % o -  3 0 . 0 % o  SUBSTRATE Range World-wide Optimum World-wide Southern Roberts Bank Range  pure firm sand to pure soft mud mixed sand and mud sand to mixed sand and mud  WAVE MOTION Range World-wide Optimum World-wide Southern Roberts Bank  waves to.stagnant water l i t t l e wave action, gentle currents gentle currents, low wave shock  DEPTH Range World-wide Optimum Puget Sound Southern Roberts Bank Range  MLLW to - 3 0 meters - 1 to - 4 meters MLLW to - 2 meters  42  f o r the narrow depth d i s t r i b u t i o n of e e l g r a s s on  southern  Roberts Bank. Den  Hartog  (19 70)  s t a t e s t h a t the depth a t t a i n e d by  e e l g r a s s depends g r e a t l y on l i g h t i n t e n s i t y and hence water clarity,  suspended m a t e r i a l s i n the water column, e t c .  The  a b i l i t y o f e e l g r a s s to extend to g r e a t e r depths i n other areas o f the P a c i f i c Coast having  c l e a r e r waters  1972,  suggests t h a t the t u r b i d  Backman and B a r i l o t t i 1976)  water of the F r a s e r R i v e r d i s c h a r g e e l e v a t e d lower River  i s r e s p o n s i b l e f o r the  l i m i t of e e l g r a s s on the  Fraser  foreshore. In F l o r i d a , Strawn  was  (Phillips  (1961)  found t h a t t i d a l exposure  the major f a c t o r i n f l u e n c i n g the zonation o f  seagrasses.  tropical  Based on a sample of s i x 1-week p e r i o d s over the  year, percentage exposures were c a l c u l a t e d f o r s i x e l e v a t i o n s i n Humboldt Bay,  northern  These determinations  California  above CD,  o f the time. 0.2  In my  study  exposed to the  air.about  area, t r a n s e c t A  (0.8m  m below MLLW), l o c a t e d j u s t i n s i d e the upper  boundary of e e l g r a s s , was the time d u r i n g 1976. ure, does indeed  exposed approximately 1 percent  of  I f d e s i c c a t i o n , and hence t i d a l expos-  c o n t r o l the upper l i m i t o f e e l g r a s s  p o s t u l a t e d by den Hartog how  1966).  i n d i c a t e d t h a t the upper l i m i t o f e e l -  grass growth (0.3 m above MLLW) was 15 percent  ( K e l l e r and H a r r i s  (1970)  and K e l l e r and H a r r i s  as (1966),  then can t h i s g r e a t d i s p a r i t y i n percentage exposure f o r  the upper l i m i t of two accounted f o r ?  P a c i f i c Coast e e l g r a s s p o p u l a t i o n s  be  The determined, as w e l l  answer l i e s  t o a g r e a t e x t e n t , by  as e x p o s u r e  provided  i n the f a c t  periods.  f o r Humboldt Bay  The  that desiccation i s  substrate characteristics o n l y sediment i n f o r m a t i o n  ( K e l l e r and H a r r i s  1966)  are  r e f e r e n c e s t o p a t c h e s o f b a r e mud  within  the e e l g r a s s  the sediment  sand.  The  i n my  holding capacity  s t u d y a r e a was  o f mud  may  account  grass h i g h e r i n the i n t e r t i d a l substrates. limits  On  f l u e n c e s the upper  the  study s i t e  f o r the presence  of  eel-  zone o f a r e a s h a v i n g muddy  tolerance  of eelgrass  distributional  limit  and  are the r e s u l t  thereby i n -  of the  changes i n s u b s t r a t e s u r f a c e  plant.  levels  observed  The  study s i t e  i s i n the l e e  t h e Tsawwassen F e r r y T e r m i n a l Causeway and p r o t e c t e d  the p r e v a i l i n g  northwest  summer w i n d s ;  ment i s t h u s m a i n t a i n e d w i t h i n bed.  During the f a l l  f r o m t h e s o u t h e a s t and action. levels  There at this  diameter)  the boundaries of the  the study s i t e  from  a depositional environeelgrass  and w i n t e r t h e p r e v a i l i n g w i n d s  i s a resultant  at  o f changes i n p r e v a i l i n g  s e a s o n a l w i n d s and wave a c t i o n . of  g r e a t e r water-  s o u t h e r n R o b e r t s Bank t h e sandy s u b s t r a t e  the exposure  Net  bed;  are  r e c e i v e s more wave  net decrease  i n sediment  surface  time of y e a r .  The  high percentage  and  o r g a n i c carbon  of fines and  (less  the p o o r l y  than sorted  0.1  mm  sediments  o b s e r v e d n e a r t h e edges o f e e l g r a s s growth p r o v i d e s t r o n g support  f o r the b a f f l i n g  e e l g r a s s bed proposed and  a c t i o n of the v e r t i c a l  by O r t h  (19 7 3 ) .  t h e p e r c e n t a g e o f f i n e s was  ( r = 0.89)  f o r the samples.  Organic carbon  positively  Carbonate  edge o f  an  content  correlated  carbon  (largely  shell  fragments) limits  infauna  correlation  (r = 0.79)  across  distribution  bed  as  Field  of organic  and  the  observations  lower  indicated that  interpretation carbonate  e e l g r a s s bed food  u p p e r and  o f b i v a l v e s were h i g h e s t My  near the  the  near the  growth.  reflects  concentrated  grass  values  populations  edges o f e e l g r a s s  strong  is  high  of e e l g r a s s growth.  benthic the  a l s o had  u p p e r and  the  carbon  i s t h a t the  abundance  of  near  infaunal  ( o r g a n i c carbon)  which  lower edges o f the  nutrient-laden currents  are  slowed  eel-  by  eelgrass. Various sideration data  as  and  aspects  of the  data  e l a b o r a t i o n to assess  gathered.  The  measurements have t h e observations.  This  salinity, limitation  limitation  the  considered.  to,  among o t h e r  three the  of the  extent  t h e measurements t a k e n general  trends  fluctuated is  during  i s uncertain  reasonable  analyses  may  changes i n a  study  and  reflected  for this  reason  i n October  for this  r e s u l t s of the  have b e e n q u i t e d i f f e r e n t  had  in  only  data.  l e v e l s o f the  p e r i o d and  t o assume t h a t t h e  for  s e s s i o n s were u n s e t t l e d ;  from the  surface  undertaken  weather c o n d i t i o n s  s a m p l e s were c o l l e c t e d  the  depth  environment  v a r i a b l e c o n d i t i o n s are  8 i n d i c a t e s that the  Secchi  p r o g r a m was  seasonal  noted e a r l i e r ,  were e x t r a p o l a t e d  Sediment Figure  the  four d i u r n a l monitoring  to which the  the  "point i n time"  estuarine  diurnal monitoring  As  of  becomes e v e n more a p p a r e n t when  are  better perspective.  validity  of being  h i g h l y v a r i a b l e c o n d i t i o n s of the  things, place  f u r t h e r con-  t e m p e r a t u r e and  the  The  require  the  1976.  substrate  reason  i t  sediment samples  been  c o l l e c t e d at some other  time.  Future s t u d i e s on the  a c t i o n s of sediments and marine angiosperms should  inter-  include  the dynamic nature of the sediments i n experimental  design  considerations.  4.  STANDING CROP, TURION DENSITY, BIOMASS AND MEASUREMENT STUDIES  4.1.  LEAF ,  M a t e r i a l s and Methods A s t r a t i f i e d random sampling technique was  determine seasonal d e n s i t y and  bed  at the upper and  lower edges of  turion  Transect  A was  e e l g r a s s bed.  The  eelgrass  established just within  upper edge o f e e l g r a s s growth and s e c t s were l o c a t e d at 0.5  Anchor  eelgrass  j o i n e d by a rope which thus b i s e c t e d the  (Figure 2).  the  the remaining f o u r t r a n -  meter depth i n t e r v a l s across  lowest t r a n s e c t , t r a n s e c t E, was  the lower l i m i t of e e l g r a s s highest  crop,  l e a f dimensions at f i v e t i d a l e l e v a t i o n s .  b l o c k s were p l a c e d growth and  changes i n e e l g r a s s s t a n d i n g  used to  and was  2.0  the  just inside  meters below  the  transect. Fifty-meter  long nylon  l i n e s , marked a t 1 meter  i n t e r v a l s , were anchored p a r a l l e l to the depth contours at 0.5  meter depth i n t e r v a l s .  such a way  The  t r a n s e c t l i n e s were p l a c e d  t h a t they were b i s e c t e d by the rope j o i n i n g  anchor b l o c k s  at the upper and  dom  number generator was  and  50  lower e e l g r a s s  used to s e l e c t two  f o r each e l e v a t i o n and  limits.  in  the A  ran-  numbers between 1  sampling s i t e s were l o c a t e d  along  t h e study  t r a n s e c t s a t these  meter  (0.5 m x 0.5 m)  steel  numbers.  A 0.25 s q u a r e  q u a d r a t was p l a c e d  on e i t h e r  s i d e o f t h e t r a n s e c t a t e a c h o f t h e two l o c a t i o n s a n d a l l o f t h e t u r i o n s r o o t e d w i t h i n t h e q u a d r a t were c l i p p e d a t sediment l e v e l  and p l a c e d  possible effects areas  i n cotton  of increased  immediately  adjacent  sacks.  insolation  To a v o i d t h e  experienced  t o sampled q u a d r a t s ,  only  by alter-  n a t e p o s s i b l e sample l o c a t i o n s were i n c l u d e d , t h a t i s t o s a y , sample s i t e s were l o c a t e d a t w h o l e m e t e r i n t e r v a l s . was u s e d  f o r underwater sampling o f the v e g e t a t i o n . Samples were t r a n s p o r t e d  and  reproductive  were t h e n washed  The  I n d i v i d u a l samples  f o r 2 minutes i n a p o r t a b l e Hoover washing and spun f o r 1 m i n u t e i n t h e  m a c h i n e t o remove a d h e r e n t w a t e r . effective  t o t h e l a b o r a t o r y and t o t a l  t u r i o n c o u n t s were made.  m a c h i n e t o remove e p i p h y t e s  very  SCUBA  The m a c h i n e p r o v e d t o be  i n removing epiphytes  w e i g h t o f t h e sample a f t e r  from t h e e e l g r a s s  leaves.  s p i n n i n g i s r e f e r r e d t o a s wet  weight. Dry minations  w e i g h t and o r g a n i c  were made f o l l o w i n g t h e t e c h n i q u e s  of Westlake  sampling  session  standing  crop  variability  and  deter-  terminology  E was n o t e s t a b l i s h e d i n t i m e f o r t h e f i r s t  (April  5 and 6, 1976) b u t an a n a l y s i s o f  (organic d r y weight) data  square meter q u a d r a t s c o l l e c t e d elevations  dry weight  (1963).  Transect  this:  (ash-free)  f r o m t h e f o u r 0.25  from each o f t h e o t h e r  i n d i c a t e d t h a t t r a n s e c t A had a h i g h e r than the o t h e r s .  The f o l l o w i n g d a t a  four  relative illustrate  Transect  The to  Coefficient  A  0.46  B  0.17  C  0.18  D  0.29  number o f samples  s i x f o r the remainder  sample v a r i a b i l i t y On A p r i l quadrat size  forthis  o f quadrat relative  size  elevation.  t o determine  t h e optimum  The f o l l o w i n g on r e l a t i v e  different  figures  variability  Coefficient of Variation  1.0  f  13.33  0.33  11.82  0.25  0.22  6.52  0.04  0.56  11.22  0.01  1.90  26.98  „  method o f B o r d e a u information. relative  indicate (sample  Percentage Standard E r r o r  0.27  Percentage  quadrat  t o t h e mean o f t h e s a m p l e ) :  Quadrat A r e a (m2)  0.5  increased  t o reduce  15, 1976 a p r o g r a m u s i n g f i v e  f o r sampling e e l g r a s s .  variability  f o r t r a n s e c t A was  o f the study p e r i o d  s i z e s was c o n d u c t e d  the e f f e c t  of Variation  s t a n d a r d e r r o r s were c a l c u l a t e d by t h e  (1953).  Appendix  6 contains additional  The 0.25 s q u a r e m e t e r q u a d r a t h a d t h e l o w e s t  variability  and i t s u s e was c o n t i n u e d f o r t h e r e m a i n  der o f the study. S e v e r a l a t t e m p t s were made t o sample t h e r o o t and rhizome  components o f t h e v e g e t a t i o n t o complement t h e l e a f  standing crop studies.  The u s e o f a c o r i n g  h o l e a u g e r met w i t h v e r y l i m i t e d  d e v i c e and a p o s t  s u c c e s s due t o t h e sandy  48 nature of the sediments,  and u n d e r w a t e r  digging  reduced  visibility  t o n i l i n a matter of seconds.  underwater  biomass  s a m p l i n g program  intertidal  biomass  sampling i n areas adjacent to t r a n s e c t  was  conducted  low t i d e s .  from A p r i l  1976  F o u r random samples  sediment  excavated and  level  tact  sieved  sorted  t h r o u g h a 0.4  (0.25  January  and  collected  samples  quadrat)  sediment  generally  Dimensions  clipped  20  The  cm  root  was  t o 30  cm,  and  l a t e r hand c l e a n e d  of the l o n g e s t i n -  random r h i z o m e  d i a m e t e r s were  from August  19 76  to  were s e l e c t e d  a t random f r o m t h e  four  a t each e l e v a t i o n d u r i n g the s i x s t a n d i n g crop  sampling s e s s i o n s o f August  l e a f o f each t u r i o n .  Intact  19 76  to January  19 77.  from the l o n g e s t  l e a v e s were i d e n t i f i e d  and  intact by  their  tips.  4.2.  S t a n d i n g Crop Eelgrass  e l e v a t i o n s on to January sampled  , The  t h e s c r e e n was  l e n g t h and w i d t h were m e a s u r e d  rounded  suitably  T u r i o n s were  screen.  sampling sessions  during  A  19 77. Two  density  cm m e t a l  i n the l a b o r a t o r y .  f o r four  date.  level,  1977  the  however,  square meter  enumerated.  r e t a i n e d by  l e a f of each t u r i o n  recorded  Leaf  later  t o the lowest r o o t  rhizome m a t e r i a l and  and  dropped;  to January  were g a t h e r e d on e a c h c o l l e c t i o n at  was  Consequently  16  19 77  during  samples  were c o l l e c t e d  occasions during (Appendix  7).  the study p e r i o d  from each o f  the p e r i o d of A p r i l  A total  five 19 76  o f 36 4 q u a d r a t s were  for leaf  standing crop  49 determinations. (1974).  A l lof the s t a t i s t i c a l  Percentage  ash c o n t e n t  dry weight  (of d r y weight)  analyses follow Zar  ( o f wet w e i g h t )  statistics  are i l l u s t r a t e d :  P e r c e n t Dry Weight  Percent Ash Content  323  Determinations  and p e r c e n t a g e  343  12.45  13.98  SD  1.68  4.79  SE  0.09  0.26  Mean  9.71  Range  A three-factor factors A (sample  (elevation)  location)  t o 18.95  5.58  analysis  and B  (time)  o f v a r i a n c e ( Z a r 19 74) fixed  random was p e r f o r m e d  and f a c t o r C  on t h e q u a d r a t  leaf  crop data.  included  i n t h e a n a l y s i s o f v a r i a n c e due t o m i s s i n g i n f o r m a -  In a d d i t i o n ,  one l o c a t i o n ,  was r a n d o m l y d e l e t e d sampling  session.  f o r each e l e v a t i o n  sampling  with  standing  tion.  The f i r s t  t o 25.72  s e s s i o n was n o t  r e p r e s e n t i n g two  from t h e t r a n s e c t A d a t a f o r each  T h i s was done so t h a t and sampling  t h e number o f s a m p l e s  t i m e were i d e n t i c a l .  a n a l y s i s o f v a r i a n c e c a l c u l a t i o n s were p e r f o r m e d calculator. and  samples,  The f o l l o w i n g n u l l  hypotheses  The  on a h a n d  were f o r m u l a t e d  tested: 1.  Ho:  O r g a n i c d r y w e i g h t p e r q u a d r a t t h e same f o r a l l five elevations  2.  Ho:  O r g a n i c d r y w e i g h t p e r q u a d r a t t h e same f o r a l l 15 s a m p l i n g t i m e s  3.  Ho:  O r g a n i c d r y w e i g h t s p e r q u a d r a t between l o c a t i o n s w i t h i n e l e v a t i o n s and t i m e s a r e t h e same  50  4.  HQ:  Organic dry weight per quadrat d i f f e r e n c e s among e l e v a t i o n s a r e i n d e p e n d e n t o f d i f f e r e n c e s among t i m e s ( i . e . , a b s e n c e o f A x B interaction)  Table leaf  standing  4 summarizes  crop;  the analysis  an e x p a n d e d v e r s i o n  of variance f o r  i s presented i n  A p p e n d i x 8.  4.2.1.  The showed t h a t for  Temporal  analysis  organic  a l l 1 5 sampling  Test  was e m p l o y e d  differences  Changes  of variance  f o r leaf standing  crop  d r y w e i g h t p e r q u a d r a t was n o t t h e same sessions.  A Newman-Keuls M u l t i p l e  t o d e t e r m i n e between which  existed.  Unfortunately,  Range  sampling  dates  the s i g n i f i c a n c e  level  f o r t h i s type o f t e s t i s the p r o b a b i l i t y o f encountering a t least  one Type  means.  I error while  session  means, t r u e  dry weights occurred.  A simpler,  sensitive, sessions  a p p r o a c h was t r i e d .  were d i v i d e d  into three  mean, i n grams o r g a n i c f o r each group. Sessions Period Mean  a l l the p a i r s o f  The t e s t was n o t p o w e r f u l enough t o d i s c e r n  among t h e 1 5 s a m p l i n g organic  comparing  (g)  a l t h o u g h much  less  The means o f t h e 1 5 s a m p l i n g groups o f f i v e  and a g r a n d calculated  The r e s u l t s w e r e :  18-June  7 - 1 1 13  8.73 This  differences i n  d r y w e i g h t p e r q u a d r a t , was  2 - 6 April  where,  information  crop p e r s i s t s a t a f a i r l y  1 2 - 1 6  June 28-Aug. 2 5  Sept.  8.40 suggests  that  28-Jan. 18 3.42  eelgrass  h i g h and c o n s t a n t  level  standing from  late  51  Table 4.  Hypothesis  4.  Analysis o f variance summary table f o r mean l e a f standing crop (organic dry weight i n grams per 0.25 square meter quadrat)  Calculated F  Conclusion  Critical F  Elevation (factor A)  16.55**  Time (factor B)  8.36**  F .01(1),14,70 = 2.35  Reject HQ  Location (factor C)  3.21**  Fo.Ol(l),70,140 = 1-60  Reject HQ  A x B  1.14ns  FO.01(1),4,70  =  3  -  6 0  0  F  0.01(l),50,70 = 1  83  Reject HQ  Accept HQ  s p r i n g u n t i l l a t e summer.  There appears t o be a d r a s t i c  d e c l i n e i n the l a t e summer and e a r l y f a l l p e r i o d d u r i n g which more than 50 percent o f the s t a n d i n g stock i s l o s t . A low and constant standing stock i s maintained of  the w i n t e r .  d u r i n g much  Appendix 7 r e v e a l s the same g e n e r a l t r e n d s .  F i g u r e 10 g r a p h i c a l l y p o r t r a y s t h i s seasonal c y c l e o f midsummer abundance, l a t e summer d e c l i n e , and reduced  standing  crop throughout the w i n t e r .  4.2.2. The  I n f l u e n c e o f Depth a n a l y s i s o f v a r i a n c e conducted f o r l e a f  s t a n d i n g crop r e v e a l e d t h a t o r g a n i c dry weight per quadrat i s not the same f o r a l l f i v e e l e v a t i o n s (F = 1 6 . 5 5 * * ) . of  Results  a Newman-Keuls M u l t i p l e Range Test show t h a t the mean  s t a n d i n g crops o f the h i g h e s t and lowest t r a n s e c t s (0.8 and -1.2  m r e s p e c t i v e l y ) a r e not s i g n i f i c a n t l y d i f f e r e n t  2.10)  from one another.  (q =  S i m i l a r l y the s t a n d i n g stocks o f the  three middle e l e v a t i o n s are not s i g n i f i c a n t l y  different  (q = 2.16) from each other; however, they are s i g n i f i c a n t l y different elevations  (q = 5.11*) from those o f the h i g h e s t and lowest (Table 5 ) . The d i f f e r e n c e s i n l e a f s t a n d i n g crops f o r the f i v e  study e l e v a t i o n s are shown i n F i g u r e 10. and e a r l y f a l l 4.2.1. (0.3,  The l a t e r summer  d e c l i n e i n s t a n d i n g stocks mentioned i n s e c t i o n  i s . very pronounced f o r the three middle e l e v a t i o n s -0.2 and -0.7 m).  Both the magnitude and r a t e o f  d e c l i n e i n l e a f standing stock are n o t i c e a b l y l e s s f o r  53  Fig.  10.  Mean l e a f s t a n d i n g c r o p (grams p e r s q u a r e meter) f o r f i v e e l e v a t i o n s ( i n r e l a t i o n t o C h a r t Datum), A p r i l 19 76 t o J a n u a r y 19 77.  90  0.8  A  r M  I 1 I  J  I  "A I S MONTH  1 6 I  N  I  D  I 7 I  Table 5. Newman-Keuls Multiple Range Test for the mean leaf standing stocks (organic dry weight i n grams per 0.25 square meter quadrat) at five elevations  Elevation (m) Ranks of Sample Means Ranked Sample Means tomparison 5 5 5 5 4 4 4 3 3 2  us 1 us 2 us 3 us 4 us 1 us 2 us 3 us 1 us 2 us 1  0.8 1 3.60  Difference  SE  5.69 4.42 1.31 0.79 4.90 3.63 0.53 4.38 3.10 1.27  .61 .61 .61 .61 .61 .61 .61 .61 .61 .61  Overall Conclusion  -1.2 2 4.88 q 9.37 7.27 2.16 1.30 8.07 5.97 0.87 7.21 5.11 2.10  0.3 3 7.98 P 5 4 3 2 4 3 2 3 2 2  -0.2 4 8.51  ^0.05,120,p  -0.7 5 9.29 Conclusion  Reject HQ* 3.917 3.685 Reject Ho* 3.356 Accept HQ Do not test 3.685 Reject HQ* Reject HQ* 3.356 Do not test 3.356 Reject HQ* 2.800 Reject Ho* 2.800 Accept HQ  0.8 = -1.2 * 0.3 = -0.2 = -0.7  t r a n s e c t s A and E (0.8 and -1.2 m, r e s p e c t i v e l y ) which are n e a r e s t the upper and lower edges o f the e e l g r a s s bed.  4.3.  Turion The  Density  v e g e t a t i v e axes o f e e l g r a s s c o n s i s t o f both  h o r i z o n t a l , indeterminate determinate growth.  rhizomes and e r e c t annual axes with  Clusters of foliage leaves,  t u r i o n s , a r i s e from both v e g e t a t i v e axes. t u r i o n s are t e r m i n a l i n Z. marina  called  Reproductive  (den Hartog 1970) and  d u r i n g the study were d i f f e r e n t i a t e d from v e g e t a t i v e t u r i o n s on the b a s i s o f t h e i r l i g h t yellow-green sympodial branching  habit.  c o l o u r and  T o t a l and r e p r o d u c t i v e t u r i o n  counts from a t o t a l o f 338 quadrats  (0.25 square meter) were  c o l l e c t e d from A p r i l  1976 t o January 1977.  analysis of variance  (Zar 1974) with  and B (time)  A three-factor  factors A (elevation)  f i x e d and f a c t o r C (sample l o c a t i o n s ) random  was conducted on the t o t a l and r e p r o d u c t i v e t u r i o n d e n s i t y data.  4.3.1.  I n f l u e n c e o f Time and E l e v a t i o n on T o t a l T u r i o n Density  T u r i o n counts were not made on a l l o f the samples from the f i r s t and second sampling s e s s i o n s  (April  1976).  To f a c i l i t a t e the t u r i o n d e n s i t y a n a l y s i s o f v a r i a n c e i n f o r m a t i o n from the f i r s t  partial  two sampling s e s s i o n s were ex-  cluded from the c a l c u l a t i o n s .  Thus, only the l a s t 14  sampling s e s s i o n s were i n c l u d e d i n the a n a l y s i s o f v a r i a n c e . To f u r t h e r f a c i l i t a t e the a n a l y s i s o f v a r i a n c e  57  c a l c u l a t i o n s data  f o r two o f the s i x quadrats from t r a n s e c t  A were d e l e t e d a t random from each sampling s e s s i o n .  Thus,  t u r i o n counts of four quadrats from each o f f i v e e l e v a t i o n s sampled on 14 occasions  were used i n the a n a l y s i s o f v a r i -  ance c a l c u l a t i o n s t o t e s t the f o l l o w i n g n u l l hypotheses: 1.  Ho:  T u r i o n d e n s i t y per quadrat i s the same f o r a l l five elevations (Factor A)  2.  Ho:  T u r i o n d e n s i t y per quadrat i s the same f o r a l l 15 sampling s e s s i o n s (Factor B)  3.  Ho:  T u r i o n d e n s i t y per quadrat between l o c a t i o n s w i t h i n e l e v a t i o n s and times i s . the same (Factor C)  4.  Ho:  T u r i o n d e n s i t y per quadrat d i f f e r e n c e s among e l e v a t i o n s are independent o f d i f f e r e n c e s among times (Absence o f A x B i n t e r a c t i o n )  Appendix 9 c o n t a i n s c o l l e c t e d d u r i n g the study. of v a r i a n c e  turion density Table  information  6 summarizes the a n a l y s i s  f o r t u r i o n d e n s i t y and Appendix 10 presents  analysis of variance Highly  information  more  f o r mean t u r i o n d e n s i t y .  significant differences i n total turion  d e n s i t y e x i s t e d between e l e v a t i o n s and times, l o c a t i o n s w i t h i n e l e v a t i o n s and times  and between  (Table 6 ) .  There was  no s i g n i f i c a n t i n t e r a c t i o n o f e l e v a t i o n and time on t o t a l turion  density. Newman-Keuls  M u l t i p l e Range T e s t s were used t o  determine which treatment means (of f i v e e l e v a t i o n s and 1 5 sessions) were d i f f e r e n t .  Table  7 shows the r e s u l t s f o r the  mean t u r i o n d e n s i t i e s o f the f i v e e l e v a t i o n s . d e n s i t i e s o f the h i g h e s t and lowest t r a n s e c t s  Turion ( 0 . 8 and - 1 . 2 m  r e s p e c t i v e l y ) were s i g n i f i c a n t l y d i f f e r e n t from one another  58  Table 6.  Analysis o f variance summary table f o r mean t o t a l turion density (turions per 0.25 square meter quadrat)  Hypothesis 1. 2. 3.  4.  Conclusion  Critical F  Calculated F  Elevation (factor A)  13.52**  Time (factor B)  8.59**  FO.Ol(l),13,70 = 2.40  Location (factor C)  2.345**  F  A x B  1.393ns  F Q . O K I ) ,50,70 = 1-83  F  0.01(l),4,70 =  3  -  6  0  0 . 0 1 ( l ) , 7 0 , 1 4 0 = 1-60  Reject HQ  Reject HQ  Reject HQ  Accept HQ  59  Table 7. Newman-Keuls Multiple Range Test for total turion density (turions per 0.25 square meter quadrat) means at five elevations  Elevation (m) Ranks of Sample Means Ranked Sample Means Comparison 5 5 5 5 4 4 4 3 3 2  vs vs vs vs vs vs vs vs vs vs  1 2 3 4 1 2 3 1 2 1  -1.2 1 9.93  Difference  SE  9.45 6.14 2.48 2.18 7.27 3.96 0.30 6.97 3.66 3.30  1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02 1.02  Overall Conclusion  -1.2  0.8 2 13.23  -0.2 3 16.89  q  p  0.3 -0.7 4 5 17.20 19.38  30.05,120,p  9.29  5  3.917  6.04  4  3.685  2.44  3  3.356  2.14  2  Do not test  7.15  4  3.685  3.90  3  3.356  0.30  2  Do not test  6.85  -3  3.356  3.60  2  2.800  3.25  2  2.800  *  0.8  *  -0.2  =  0.3  =  0.7  Conclusion Reject Ho* Reject H Q Accept H Q Reject H Q * Reject H Q * Reject H Q * Reject H Q * Reject H Q *  60 and  from the  significant (-1.2  m)  three  differences  had  the  square meter). f r o m 67  to  t i o n had  middle e l e v a t i o n s ,  77  an  lowest  existed.  The  lowest  turion density  Densities turions  between w h i c h  f o r the  per  intermediate  (40  elevations  turions  per  middle e l e v a t i o n s  square meter. density  no  (53  The  ranged  highest  turions  per  eleva-  square  meter). The clusive  Newman-Keuls M u l t i p l e  results  sessions.  19 74).  showing a d e c l i n e  by  Figure  turion density  general  timing  of  elevations;  there  in  and  the  rate  elevations. turions time three as  in total  per  f o r the  f r o m summer  transect  the  had  u p p e r and  rate  decline  l o s s per  square meter) o f  i s halved  great  between  (approximately  D u r i n g the  summer  t u r i o n d e n s i t i e s t w i c e as  the  f o r these middle  The  differences  reached a t the  lower e l e v a t i o n s  in  for a l l  i n density  turion density  ( t u r i o n l o s s per  to  elevations.  seems c o n s t a n t  for a l l elevations.  the  trend  seasonal decline  s q u a r e meter) a p p e a r s t o be  both the  much g r e a t e r  five  magnitude o f  middle e l e v a t i o n s  those of  the  ambiguous  treatment  seasonal  however, a p p e a r t o be  Similar winter  (October)  produces  Summer t u r i o n d e n s i t y depicts  incon-  densities  numbers o f  overall  turion losses do,  often  turion density  8. 11  test  large  However, an  i s seen i n T a b l e  mid-winter.  total  This  f o r comparisons w i t h  (Zar  winter  gave  r e s u l t s f o r c o m p a r i s o n s o f mean t u r i o n  between s a m p l i n g  means  Range T e s t  and,  u n i t t i m e ) and  40  same the great  consequently,  extent  (turion  o b s e r v e d d e c l i n e must have b e e n elevations.  Table 8.  T o t a l t u r i o n densities (turions per 0.25 square meter quadrat) f o r fourteen sampling sessions, May t o December 1976  Ranks o f Sample Means 1 2 3 4 5 6 7 8 9 10 11 12 13 14  Ranked Sample Means  Month Sampled  22.95 21.90 21.05 20.05 18.95 16.55 15.30 14.65 13.00 11.60 10.70 10.15 9.20 8.50  May May July June August May June August July September January November October December  62  Fig.  11.  Mean t o t a l t u r i o n numbers p e r s q u a r e m e t e r f o r f i v e e l e v a t i o n s ( i n r e l a t i o n t o C h a r t Datum), A p r i l 1976 t o J a n u a r y 1977.  63  A  f  M  I  ~J  I  3  n  A I S MONTH  I  0  I  N  I  fj  I  J  I  4.3.2.  I n f l u e n c e o f Time and E l e v a t i o n on Reproductive Turion Density  A two-factor c a t i o n was  a n a l y s i s of variance without  p e r f o r m e d on  information  the  ( A p p e n d i x 11)  reproductive  collected  the p e r i o d i n which r e p r o d u c t i v e t o A u g u s t ) no  significant  d e n s i t i e s were f o u n d (Table 9 ) ,  b u t may  reproductive  turion  elevation before  4.4.  The per To  weight per gression  was  had  the  essentially  i t began a t the  are  The  highest  and  completed lowest  a t the  relationship  was  c a l c u l a t e d f o r each o f the  dry weight  The  equations  five  re-  five and  linear  ( d e p e n d e n t v a r i a b l e ) on  v a r i a b l e ) f o r the 10.  The  dry  linear  (per quadrat)  data.  highest  of organic  e l e v a t i o n , a simple  quadrat)  eleva-  Weight  equation  (grams p e r  middle  elevations.  Organic  density  Peak  lowest  tidal  turion  11.  reproductive  and  i n Table  turion  times  three  turion  crop  (May  apparent i n  of Appendix  July.  o f D e p t h on  i n v e s t i g a t e the  (independent  presented  trends  density data  than  Influence Turion  sion of organic number  general  d u r i n g J u n e and  e l e v a t i o n s u s i n g the standing  During  t u r i o n s were p r e s e n t  a longer p e r i o d d u r i n g which  Flowering  study.  between e l e v a t i o n s o r s a m p l i n g  t u r i o n s were p r e s e n t tions.  the  occur.  flowering occurred e l e v a t i o n s had  during  density  differences i n reproductive  However, c e r t a i n the  turion  repli-  regresturion  elevations i s  indicate that  the  65  Table 9.  Analysis o f variance summary table f o r mean reproductive turion density (turions per square meter)  Source o f V a r i a t i o n  Total Elevation Time Remainder  SS  DF  MS  46.97  27  11.13  4  2.78  4.57  5  0.91  31.27  18  1.74  To t e s t H Q :  No difference among elevations. Calculated F = 1.60 Fo.05(1),4,18 = 2.93ns  To t e s t H Q :  N O difference among times. Calculated F = 0.53 FQ.05(1),5,18 = 2.77ns  , Table 10.  Elevation (CD) 0.8 m 0.3 m -0.2 m -0.7 m -1.2 m  Linear regression equations of organic dry weight (g) on turion numbers per quadrat for five elevations  Number of Observations 88 64 62 64 60  Equation Y Y Y Y Y  = = = = =  0.21 0.51 0.56 0.45 0.53  x +0.79 x -0.71 x -1.34 x -0.06 x -0.57  Coefficient of Determination 0.57 0.64 0.80 0.68 0.78 *  67 regression for  coefficient  the highest  other  elevation  of the best  (0.8 m)  line  from those o f t h e  of variance  p r o c e d u r e was u s e d t o t e s t  s i g n i f i c a n c e o f each o f the r e g r e s s i o n s .  h y p o t h e s i s HQ: P highly  = 0 was r e j e c t e d  significant The  differences  next s t a t i s t i c a l  between t h e r e g r e s s i o n s hypothesis that elevations) ficant  c a l c u l a t e d F value  Multiple  Range T e s t  different of.the m)  slopes  were e q u a l was  f i t regression  o f the regressions i s that  much l o w e r  foliage  elevations. lation  taken  for significant  (Table  an  differences  elevations.  rejected  The  regressions  null  (for five  due t o t h e h i g h l y  11).  A  Table  line  signi-  Newman-Keuls  f o r the highest difference  o f the highest  (per turion) t h e same  from the l e a f  that  were  the  slope  elevation from the  f o r the other e l e v a t i o n s .  the turions  Using,  12 r e v e a l s  significant  as  (Appendix 12).  was u s e d t o d e t e r m i n e w h i c h s l o p e s  exhibits a highly  pretation  elevations  f o r each  of a l l five  from which o t h e r s .  best  null  p r o c e d u r e employed was  of the f i v e  the slopes  The  for a l l five  existed  analysis of covariance testing  (0.8  differs  f i t regression  elevations. An a n a l y s i s  the  (slope)  My  inter-  e l e v a t i o n have a  than i s found a t the lower .data  standing  the following c r o p and t u r i o n  calcu-  density  analyses of variance i s recorded. Elevation .Organic D r y W e i g h t Turion Density O r g a n i c Dry Weight per Turion  (g) (g)  0.8  0.3  3.60 13.23 0.27  7.98 17.19 0.46  (m)  -0.2  -0.7  8.51 16.89 0.50  9.29 19.37 0.48  -1.2 4.87 9.93 0.49  68  Table 11. Analysis o f covariance summary t e s t i n g f o r s i g n i f i c a n t differences between slopes o f l i n e a r regression l i n e s o f organic dry weight on turion numbers f o r f i v e elevations  Regression  Number o f Observations  Regression Coefficient  Residual SS  Residual DF  Elevation (m) 0.8 0.3 -0.2 -0.7 -1.2  88 64 62 64 ' 60  Pooled Common  0.21 0.51 0.57 0.45 0.53  96.98 586.75 489.28 524.51 182.83  0.45  1880.35 4669.32  Calculated F = 12.62** Fo.Ol(l),4,300 = 3.38 Conclusion:  Reject %:£().8 = £ 0 . 3 = £ - 0 . 2 = £ - 0 . 7 = £ - 1 . 2  86 62 60 62 58  69  Table 12. Newman-Keuls Multiple Range Test for differences between slopes of linear regressions of organic dry weight on turion numbers for five elevations  Elevation (m) Ranks of Regression Coefficients Ranked Regression Coefficients  0.8 1 0.21  Comparison  q  5 5 5 5 4 4 4 3 3 2  vs vs vs vs vs vs vs vs vs vs  Difference  SE  0.3 3 0.51  -0.2 5 0.57  p  30.01,300,p  -0.7 -1.2 2 4 0.45 0.53  1  .36  .032  11.42  5  4.603  2  .12  .038  3.11  4  4.403  3  .07  .042  1.55  3  4  .05  .041  1.15  2  Do not test Do not test  1  .32  .027  4  4.403  2  .07  .042  1.70  3  3  .02  .046  0.41  2  Do not test Do not test  1  .30  .037  8.12  3  4.120  2  .05  .044  1.21  2  Do not test  1  .25  .033  3.38  2  3.643  11.66  Overall Conclusion of Slopes  Conclusion Reject H Q Accept Ho Reject H Q Reject H Q Reject H Q  0.8 ^ 0.3 = -0.2 = -0.7 = -1.2  70  4.5.  Biomass I n t e r t i d a l e e l g r a s s biomass was sampled d u r i n g low  t i d e s from A p r i l 1976 t o January 19 77.  Sampling  sessions  were undertaken a t approximately 1-month i n t e r v a l s and were conducted d u r i n g very low t i d e s when the i n t e r t i d a l e e l g r a s s was exposed. program are contained  The r e s u l t s o f the biomass sampling i n Appendix 13.  and below s u b s t r a t e p a r t s were constant 1976  (Table 1 3 ) .  Percentages o f above from A p r i l t o J u l y  A drastic decline i n i n t e r t i d a l  leaf  s t a n d i n g crop i n August 19 76 g r e a t l y a l t e r e d the r a t i o i n subsequent samplings.  Rhizome standing  crop d i d not appear  to change d u r i n g the sampling p e r i o d . During the s p r i n g and e a r l y summer the l e a f s t a n d i n g crop was about two-thirds s t a n d i n g crops  about o n e - t h i r d o f the t o t a l biomass.  l a t e summer and f a l l  the above and below s u b s t r a t e  each c o n s t i t u t e d about 50 percent  4.6.  and the r o o t and rhizome By  portions  o f the biomass.  Leaf Measurements Leaf l e n g t h and width were measured on the l o n g e s t  i n t a c t l e a f o f each t u r i o n c o l l e c t e d d u r i n g the r e g u l a r standing  crop and t u r i o n d e n s i t y sampling s e s s i o n s  August 1976 t o January 1977. i n Table  14.  The i n f o r m a t i o n  from  i s summarized  There i s a g e n e r a l d e c l i n e i n l e a f width from  August t o January f o r a l l f i v e e l e v a t i o n s .  A similar decline  i n l e a f l e n g t h i s apparent f o r the same p e r i o d but there i s  Table 13.  Percentages o f above substrate (leaf) and below substrate (roots and rhizomes) standing crops, A p r i l 1976 t o January 1977  Date  Percentage Above Substrate  Percentage Below Substrate  16.4.76 15.5.76 12.6.76 10.7.76 7.8.76 24.8.76 25.10.76 23.11.76 17.1.77  61.9 72.7 67.2. 64.4 42.1 49.8 56.1 47.3 53.0  38.1 27.3 32.8 35.6 57.9 50.2 43.9 52.7 47.0  Mean  59.3  40.7  72  Table 14. Leaf measurements f o r f i v e elevations, August 1976 t o January 1977  E l e v a t i o n (m) 0.8  0.3  -0,2  -0.7  -1.2  102,.8 9,.37 80,.7 9 .65 49 .7 11 .23 54 .7 5,.71 42 .7 5 .72 41 .4 3 .91  99,.9 8,.03 87 .9 7 .90 69 .3 9 .40 40 .5 4 .63 55 .0 6 .90 41 .0 2 .23  94,.5 8,.25 69,.8 9,.56 70,.3 8,.30 60,.7 7,.85 54,.0 11,.37 42 .6 2 .96  Leaf Length (cm) August September October November December January  . Mean SE Mean SE Mean SE Mean SE Mean SE Mean SE  54..9 5.,53 56.,0 4.,09 55.,0 5.,67 39.,3 3..45 39..6 3.;43 31.,6 '3..89  104.,3 20.,0 71.,4 8.,51 59.,3 8..11 42..6 6..79 45..6 4..30 29..6 2..61  Leaf Width (cm) August September October November December January  Mean SE Mean SE Mean SE Mean SE Mean SE Mean SE  0..61 0..022 0..58 0..027 0..51 0,.028 0,.53 0,.021 0,.52 0,.025 0,.50 0,.025  0..69 0,.058 0..62 0,.029 0,.57 0,.028 0,.56 0,.043 0,.54 0 .022 0 .40 0 .017  0 .60 0 .029 0 .65 0 .027 0 .61 0 .040 0 .49 . 0.020 0 .54 0 .033 0 .52 0 .020  0 .66 0 .031 0 .60 0 .026 0 .56 0 .039 0 .46 0 .019 0 .57 0 .025 0 .58 0 .016  0 .66 0 .036 0 .56 0 .041 0 .55 0 .031 0 .56 0 .029 0 .52 0 .037 0 .58 0 .023  a s t r i k i n g d i s s i m i l a r i t y between the h i g h e s t e l e v a t i o n (0.8 m) and the o t h e r s .  In August, mean l e a f l e n g t h f o r  the h i g h e s t e l e v a t i o n i s approximately one-half other e l e v a t i o n s .  t h a t o f the  By January, mean l e a f l e n g t h f o r the  upper e l e v a t i o n has been reduced by 40 p e r c e n t ;  however,  mean l e a f l e n g t h f o r the other e l e v a t i o n s has d e c l i n e d by about 60 p e r c e n t .  Mean w i n t e r  l e a f length  (of the l o n g e s t  i n t a c t l e a f on each t u r i o n ) appears t o be the same f o r a l l f i v e e l e v a t i o n s and thus the lower e l e v a t i o n s experience g r e a t e r and more r a p i d change i n mean l e a f l e n g t h the f a l l .  a  during  There appears t o be a time l a g a s s o c i a t e d  with  i n c r e a s i n g depth f o r the observed changes i n mean l e a f length.  In August the 0.3 and -0.2 m e l e v a t i o n s had the  g r e a t e s t mean l e a f l e n g t h , i n September the -0.2 and -0.7 m e l e v a t i o n s , October the lowest two e l e v a t i o n s , and by November the g r e a t e s t mean l e a f l e n g t h was observed a t the lowest e l e v a t i o n . Table  15 shows the same seasonal  decline i n leaf  l e n g t h and width o f samples c o l l e c t e d adjacent  t o the 0.8 m  e l e v a t i o n f o r the biomass determinations January 1977).  Disregarding  (August 19 76 t o (Vide Table 14) the anomalous r e a d i n g s f o r v  August, which may be l a r g e l y a t t r i b u t e d t o sampling e r r o r , the other values are s i m i l a r t o those obtained r e g u l a r sampling s e s s i o n s  (Table 1 4 ) .  d u r i n g the  The changes i n mean  rhizome diameter are d i f f i c u l t t o i n t e r p r e t because o f the r e l a t i v e l y s h o r t p e r i o d i n which measurements were taken. During e x c a v a t i o n  the rhizomes were o f t e n c u t with the shovel  74  Table 15. Leaf and rhizome measurements f o r samples c o l l e c t e d a t 0.8 meters ( i n r e l a t i o n t o Chart Datum), August 1976 t o January 1977. Number o f observations i n brackets  Aug. 76  Oct. 76  Nov. 76  Jan. 77  Leaf Length (cm)  Mean SE  30 .80 (87)1 .08  55 .48 (27) 4 .76  48 .74 (22) 4 .39  26.89 (43) 1.43  Leaf Width (cm)  Mean SE  0 .45 (87) 0 .01  0 .54 (27) 0 .02  0 .56 (22) 0 .03  0.47 (43) 0.01  Rhizome Diameter (cm)  Mean SE  0 .37 (87) 0 .02  . 0.41 (92) 0 .01  0 .47 (61) 0 .01  0.40 (96) 0.01  blade.  As  d i a m e t e r s were m e a s u r e d on  s e g m e n t s , e a c h r h i z o m e may times i n each  4.7.  ductive  influence of eelgrass  factors associated with  Leaf  indicate that  corresponds to the typiea)  of  latifolia  standing  i n several other  s e c t i o n 1.2.).  Scagel was  not  the  eelgrass  (1961).  The  increased  length with  s u p p o r t e d by On the  three  northern  (Z. marina  seagrasses  the  marina  study.  var. var.  Leaf  dimen-  s i m i l a r to those of  The  greater  this  Puget  r e l a t i o n s h i p s of  depth d e s c r i b e d  for  (Phillips  Keller  1972,  (Strawn 1961)  other  study.  of eelgrass  studied,  g r o w t h and  distribution.  intermediate  the  California.  K e l l e r and  Harris  t u r i o n d e n s i t y was  at  the lower  (1966)  turion density  I n P u g e t Sound, W a s h i n g t o n  intertidal  near  lowest near the  same r e l a t i o n s h i p o f d e p t h and  found t h a t  and  i s further  R o b e r t s Bank, t u r i o n d e n s i t i e s were h i g h e s t  of eelgrass  found the  (19 72)  this  are  populations  other  form  l a r g e r f o r m Z.  19 7 2 ) .  middle e l e v a t i o n s  upper l i m i t limit  and  studies  s o u t h e r n R o b e r t s Bank  encountered during  (Phillips  1966)  of  repro-  have b e e n  Coast eelgrass  short, narrow-leafed  Coast eelgrass  and  measurements t a k e n d u r i n g  Sound e e l g r a s s  Pacific  stocks  Pacific  s i o n s o f R o b e r t s Bank e e l g r a s s  leaf  tidal  l e a f dimensions, vegetative  t u r i o n d e n s i t i e s and  investigated  Harris  several  Discussion  e l e v a t i o n on  study  have b e e n r e p r e s e n t e d  sample.  The  (see  i n d i v i d u a l rhizome  in  Phillips five  times  as great as s u b t i d a l t u r i o n d e n s i t y i n the c l e a r waters i  surrounding  Bush P o i n t and only twice as g r e a t i n the t u r b i d  waters o f f A l k i P o i n t .  Both Puget Sound study s i t e s a l s o  e x h i b i t e d a decrease i n t u r i o n d e n s i t y with i n c r e a s i n g depth.  E e l g r a s s d e n s i t y on Roberts Bank i s low compared t o  other P a c i f i c Coast e e l g r a s s p o p u l a t i o n s K e l l e r 1963, information  Stout  1976)  ( P h i l l i p s 1972,  and a l a c k o f comparable h a b i t a t  (e.g. water c l a r i t y )  from these other  areas  l i m i t s s p e c u l a t i o n as t o the reasons f o r these r e g i o n a l differences i n population The  characteristics.  ,  f i n d i n g s o f t h i s study r e v e a l t h a t the mean l e a f  standing crops o f the h i g h e s t and lowest e l e v a t i o n s were s i g n i f i c a n t l y lower than the mean l e a f standing  crops o f the  three middle e l e v a t i o n s , which, i n t u r n , were not s i g n i f i c a n t l y d i f f e r e n t from each o t h e r . i standing  T h i s r e l a t i o n s h i p o f reduced  crop near the upper and lower l i m i t s o f growth i s  s i m i l a r t o t h a t r e p o r t e d by K e l l e r and H a r r i s California.  (1966) i n  The standing crop values o f e e l g r a s s on Roberts  Bank c l o s e l y resemble the values obtained a t h i s A l k i P o i n t , Washington study s i t e .  by P h i l l i p s  (1972)  The standing  crops  o f e e l g r a s s a t A l k i P o i n t , where the water was t u r b i d , were much lower than a t h i s Bush P o i n t study s i t e , where the water was c l e a r e r .  S i m i l a r l y , t o t a l biomass a t A l k i  was much lower than a t Bush P o i n t .  Both standing  Point  crop and  biomass appear t o be s t r o n g l y i n f l u e n c e d by water c l a r i t y . Sampling d i f f i c u l t i e s d i d not allow me t o c o l l e c t on s u b t i d a l biomass.  information  I n t e r t i d a l biomass o f e e l g r a s s on  southern Roberts Bank i s comparable t o the biomass o f one o f  the i n t e r t i d a l s t a t i o n s a t A l k i P o i n t , Washington  (Phillips  1972). Seasonal changes i n v e g e t a t i v e and  reproductive  t u r i o n d e n s i t i e s , l e a f s t a n d i n g crop, biomass and,  to a  l i m i t e d e x t e n t , l e a f measurements have been s t u d i e d i n Puget Sound, Washington by P h i l l i p s c o l l e c t e d d u r i n g t h i s study  (1972).  The  information  i n d i c a t e s t h a t southern  Roberts  Bank e e l g r a s s undergoes seasonal c y c l e s s i m i l a r to Puget Sound e e l g r a s s .  For both l o c a t i o n s , l e a f s t a n d i n g crop  and  t u r i o n d e n s i t y reach minimum values i n January and maximum values  from May  to J u l y .  However, P h i l l i p s d i d not  record  the g r e a t l o s s e s i n l e a f s t a n d i n g crop and t u r i o n d e n s i t i e s in  the l a t e summer which were observed i n t h i s  Previous  s t u d i e s on e e l g r a s s p r o d u c t i v i t y and  have not c o n s i d e r e d  t h i s reason may  production.  l e a f dynamics  the l o s s of whole t u r i o n s as b e i n g a  s i g n i f i c a n t f a c t o r i n the d e t e r m i n a t i o n for  study.  of net  production.and  have g r o s s l y underestimated a c t u a l net  P h i l l i p s d i d not r e p o r t seasonal  changes i n mean  l e a f dimensions but d i d f i n d t h a t r e p r o d u c t i v e t u r i o n s appeared i n A p r i l i n Puget Sound.  On  southern  first  Roberts Bank,  r e p r o d u c t i v e e e l g r a s s t u r i o n s were f i r s t observed i n mid-May and had  disappeared  shortened  by mid-August.  The  reasons f o r the  r e p r o d u c t i v e season observed d u r i n g t h i s  study  were not i n v e s t i g a t e d ; however, Backman and B a r i l o t t i  (1976)  found t h a t f l o w e r i n g i s a f f e c t e d by reduced i r r a d i a n c e . The  t u r b i d e s t u a r i n e waters of Roberts Bank reduce the  amount of l i g h t a v a i l a b l e to e e l g r a s s and  a similar  inhibition  78 in  f l o w e r i n g may be t h e r e s u l t  this  o f reduced  irradiance i n  area. D u r i n g t h e s t u d y , two p r o b l e m a r e a s a r o s e  warrant of  f u r t h e r comment i n r e g a r d  seagrasses.  of t h e study grass  bed.  within  to future investigations  One o f t h e c r i t e r i a  used i n the s e l e c t i o n  s i t e was t h e a p p a r e n t h o m o g e n e i t y o f t h e e e l No a r e a s o f b a r e  substrate  g r o w t h were o b s e r v e d a t t h e s t u d y collected  indicate that  the eelgrass  meadow.  o r sparse  site;  considerable  between l o c a t i o n s w i t h i n  Highly  standing  eelgrass ated  crop  (Table  plants within  i n t o sampling  patchiness  originate  for  root  5).  (Table  6) a n d  The p a t c h y d i s t r i b u t i o n o f meadow s h o u l d  total  o f sampling  Consistent  t o rhizome t o shoot r a t i o s  be i n c o r p o r -  investigations.  i n t r y i n g t o assess  i n the d i f f i c u l t i e s  weight determinations  differences  study e l e v a t i o n s and s a m p l i n g  an e e l g r a s s  components o f e e l g r a s s .  existed  significant  schemes o f f u t u r e  problems encountered  eelgrass  however, t h e d a t a  s e s s i o n s were f o u n d f o r b o t h t u r i o n d e n s i t y leaf  which  plant  the root  The biomass  and r h i z o m e  r e s u l t s were n o t o b t a i n e d or f o r the organic dry  o f t h e s e components d u r i n g  the study,  e v e n a f t e r l a b o r i o u s hand s o r t i n g a n d c l e a n i n g o f t h e r o o t s and  rhizomes.  A much g r e a t e r  approach and t e c h n i q u e w i l l and  useful  results.  degree o f s o p h i s t i c a t i o n i n  be r e q u i r e d  to obtain  consistent  79 5.  SUMMARY AND  The  CONCLUSIONS  r e s u l t s o f the study  each s e c t i o n .  have b e e n d i s c u s s e d i n  The p u r p o s e o f t h i s  to synthesize the previous  p o r t i o n o f the study i s  d i s c u s s i o n s and f i n d i n g s i n v i e w  of the s t a t e d o b j e c t i v e s o f the study. The southern  Roberts  encountered light.  d i s c u s s i o n o f e e l g r a s s h a b i t a t f a c t o r s on Bank showed t h a t t h e r e s t r i c t e d  t h e r e was t h e r e s u l t  o f d e s i c c a t i o n and  In a d d i t i o n , the d i s c u s s i o n o f t u r i o n  leaf  standing crops  cant  d i f f e r e n c e s e x i s t e d f o r some o f t h e s e  the  different  and l e a f d i m e n s i o n s  study  elevations.  f a c t o r s o f the study morphological, eelgrass  site  relate  a t the study  site?  controlling  the b a s i s o f l e a f  to three  to deal with  i t s u p p e r and l o w e r  tidal  zones.  densities  lower  i n this  Roberts  standing crop,  three d i s t i n c t  growth, c o m p a r a t i v e l y  other  environmental  t o the d i f f e r e n c e s i n  information presented  measurements, i n t o  at  parameters a t  What a r e t h e a d a p t i v e  the eelgrass o f southern  turion  signifi-  the depth distribu-  limits? The  on  reduced  b i o m a s s and p o p u l a t i o n ^ c h a r a c t e r i s t i c s o f  dependent f a c t o r s  that  range  densities,  showed t h a t  How do t h e  s t r a t e g i e s which e e l g r a s s has e v o l v e d  tional  depth  Bank c a n be g r o u p e d ,  turion  d e n s i t y and l e a f  c a t e g o r i e s which  Near t h e upper l i m i t low s t a n d i n g c r o p s  are observed.  study i n d i c a t e s  Mean l e a f  correspond  of eelgrass  and i n t e r m e d i a t e length i s less  e l e v a t i o n s , as i s o r g a n i c d r y w e i g h t p e r t u r i o n .  areas,  than In  t h e upward e x t e n s i o n o f e e l g r a s s d e p e n d s g r e a t l y  80 on the degree o f ' d e s i c c a t i o n " (den Hartog 1970); reduced blade l e n g t h appears t o be the adaptive mechanism employed by e e l g r a s s i n response to i n c r e a s e d e s i c c a t i o n on .Bank.  The  Roberts  three middle e l e v a t i o n s s t u d i e d e x h i b i t e d high  t u r i o n d e n s i t i e s and  l a r g e l e a f standing  crops.  Mean l e a f  l e n g t h and mean o r g a n i c dry weight per t u r i o n were g r e a t e r than a t the h i g h e s t e l e v a t i o n .  I t appears t h a t  c o n d i t i o n s f o r e e l g r a s s growth and the i n t e r m e d i a t e The  optimal  development are found at  p o r t i o n s of the depth range o f e e l g r a s s .  lowest e l e v a t i o n (-1.2  m)  had  the lowest mean t u r i o n  d e n s i t y o f a l l and y e t maintained an i n t e r m e d i a t e standing crop.  Leaf  leaf  l e n g t h and o r g a n i c dry weight per t u r i o n  were the same as those o f the middle e l e v a t i o n s .  Near the  lower d i s t r i b u t i o n a l l i m i t , e e l g r a s s responds to decreased l i g h t i n t e n s i t y by reducing l i m i t i n g s e l f - s h a d i n g may and  turion density.  become an important  Where l i g h t i s consideration  a mechanism which w i l l reduce t u r i o n d e n s i t y , and  thus  shading w i l l be advantageous to the p l a n t . The 1.  The  major c o n c l u s i o n s  of the study are:  s a l i n i t y , temperature and water motion c o n d i t i o n s  of  southern Roberts Bank are c l o s e t o the world-wide optima f o r e e l g r a s s growth. 2.  The  r e s t r i c t e d depth d i s t r i b u t i o n of e e l g r a s s on  Roberts Bank i s due  to the l i g h t environment and  c h a r a c t e r i s t i c s of the 3.  southern substrate  area.,  Reduced l i g h t a v a i l a b i l i t y i n the t u r b i d e s t u a r i n e waters of southern Roberts Bank i s r e s p o n s i b l e f o r the  elevated  81 lower d i s t r i b u t i o n a l l i m i t o f e e l g r a s s found 4.  there.  The sandy nature o f the sediments o f the study  area  c o n t r o l s the upper d i s t r i b u t i o n a l l i m i t o f e e l g r a s s on southern Roberts 5.  Bank.  Sediments w i t h i n an e e l g r a s s bed experience  pronounced  seasonal changes i n s u r f a c e l e v e l s . 6.  F i n e sediment f r a c t i o n s and p a r t i c u l a t e o r g a n i c matter are c o n c e n t r a t e d near the edges o f e e l g r a s s meadows.  7.  E e l g r a s s undergoes pronounced seasonal changes i n l e a f  1  s t a n d i n g crop and t u r i o n d e n s i t y ; a l a r g e d e c l i n e i n both takes p l a c e i n l a t e summer. 8.  F l o w e r i n g o f e e l g r a s s on southern Roberts  Bank occurs  from  mid-May t o mid-August; t h i s r e l a t i v e l y s h o r t r e p r o d u c t i v e season observed  may be the r e s u l t o f reduced  light  availability. 9.  Leaf s t a n d i n g crops are lower near the upper and lower l i m i t s o f e e l g r a s s beds.  Leaf s t a n d i n g crop i s g r e a t e s t  at i n t e r m e d i a t e e l e v a t i o n s . 10.  Turion density i s highest at intermediate e l e v a t i o n s , lower near the upper edge o f the e e l g r a s s bed and lowest near the s u b t i d a l d i s t r i b u t i o n a l l i m i t o f e e l g r a s s growth.  11.  Organic dry weight p e r t u r i o n near the upper edge o f . e e l g r a s s growth i s approximately  one-half o f the value  of lower e l e v a t i o n t u r i o n s . 12.  During the summer the mean l e a f l e n g t h near the upper edge of the e e l g r a s s bed i s approximately  o n e - h a l f o f the mean  l e n g t h o f leaves from lower e l e v a t i o n s ; i n w i n t e r mean  leaf 13.  length  The r a t i o standing  14.  o f above s u b s t r a t e crops  Reduced l e a f desiccation  15.  i s t h e same f o r a l l e l e v a t i o n s .  i s 2:1; d u r i n g  length  winter  substrate the r a t i o  i s 1:1.  a p p e a r s t o be a r e s p o n s e t o  i n eelgrass.  Reduced t u r i o n d e n s i t y reduced  t o below  a p p e a r s t o be a r e s p o n s e t o  light a v a i l a b i l i t y i n eelgrass.  83  GLOSSARY  5  84 Biomass.  The w e i g h t o f a l l p a r t s o f a l l t h e p l a n t s on a u n i t area a t a given time.  Carbonate carbon. C a r b o n a t e c a r b o n was u s e d as an i n d i r e c t measure o f b e n t h i c b i v a l v e p o p u l a t i o n s i n t h i s study. The s o u r c e o f c a r b o n a t e i n m a r i n e sediments i s g e n e r a l l y s h e l l fragments. Chart  Dry  Datum (CD). I n C a n a d a , C h a r t Datum r e p r e s e n t s t h e plane o f lowest normal t i d e s . In the t e x t p o s i t i v e and n e g a t i v e e l e v a t i o n s r e f e r t o e l e v a t i o n s above and b e l o w t h e s p e c i f i e d r e f e r e n c e p l a n e (MLLW o r C D ) .  weight. The w e i g h t o f p l a n t m a t e r i a l a f t e r h e a t i n g i n z an o v e n a t 105OC t o c o n s t a n t w e i g h t .  Fines.  F o r the purpose o f t h i s study the sediments which p a s s e d t h r o u g h t h e f i n e s t (0.1 mm) s i e v e a v a i l a b l e c o n s t i t u t e d the fine f r a c t i o n .  Fresh weight.  The t r u e w e i g h t o f t h e l i v i n g  plant.  Organic  carbon. The o r g a n i c c o n t e n t o f a s e d i m e n t r e f l e c t s t h e amount o f p a r t i c u l a t e p l a n t and a n i m a l r e s i d u e s p r e s e n t and t h u s p r o v i d e s a r o u g h e s t i m a t e o f t h e food a v a i l a b l e f o r f i l t e r feeding infauna f o r the purposes of t h i s study.  Organic  dry weight. The l o s s i n w e i g h t o f p l a n t m a t t e r a f t e r i g n i t i o n a t 550°C. A l s o known as a s h - f r e e d r y weight.  Prostrate. Quadrat.  Horizontal, trailing  along  the ground.  A square o r r e c t a n g u l a r area sample v e g e t a t i o n . A 0.25 m was u s e d i n t h i s s t u d y .  2  Reproductive Rhizome.  turion.  used t o q u a n t i t a t i v e l y (0.5 x 0.5 m) q u a d r a t  An e r e c t stem b e a r i n g i n f l o r e s c e n c e s .  H o r i z o n t a l , elongated,  subterranean  stem.  Secchi disc. A round white d i s c which i s lowered i n t o the w a t e r column t o p r o v i d e an e s t i m a t e o f t h e t r a n s m i s s i o n o f v i s i b l e l i g h t i n w a t e r and h e n c e , water c l a r i t y . Standing  crop. The w e i g h t o f p l a n t m a t e r i a l t h a t c a n be s a m p l e d o r h a r v e s t e d by n o r m a l methods, a t any one time, from a g i v e n a r e a . Does n o t n e c e s s a r i l y include a l l parts of plants or a l l plants.  85 Sympodial Branching. O c c u r s when t h e t e r m i n a l bud l o s e s i t s c a p a c i t y f o r a c t i v e g r o w t h and a l l s u b s e q u e n t growth o c c u r s a t t h e a u x i l i a r y s h o o t s . Total  turion density. T o t a l number o f t u r i o n s and r e p r o d u c t i v e ) per u n i t area.  Turion.  (vegetative  A c l u s t e r o f f o l i a g e l e a v e s a r i s i n g from a v e g e t a t i v e axis. Common u s a g e d o e s n o t a d h e r e t o t h e c o r r e c t b o t a n i c a l d e f i n i t i o n which d e s c r i b e s a t u r i o n as a w i n t e r bud o n some w a t e r p l a n t s t h a t becomes d e t a c h e d , o v e r w i n t e r s , and u n d e r f a v o r a b l e c o n d i t i o n s d e v e l o p s a new p l a n t .  Vegetative  turion. A non-reproductive bearing inflorescences).  turion  Wet w e i g h t . Experimental value obtained a f t e r adherent water from p l a n t m a t e r i a l .  (i.e., not removing  BIBLIOGRAPHY  87 Backman, T. W. and D. C. B a r i l o t t i . 19 76. Irradiance r e d u c t i o n : e f f e c t s on s t a n d i n g c r o p s o f t h e e e l g r a s s Zostera marina i n a c o a s t a l lagoon. Mar. B i o l . 34: 33-40. Black,  C.  A. e t a l . ' ( e d s . ) . 1965. Methods o f s o i l a n a l y s i s . Am. Soc. A g r o n . , Monogr. No. 9. 1,572 pp.  B o r d e a u , P. F. 1953. 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I n c . , New J e r s e y . 620 pp.  Prentice-Hall,  91  APPENDICES  92  APPENDIX 1:  Date  31.3.76 2.4.76 3.4.76 5.4.76 6.4.76 19.4.76 3.5.76 14.5.76 31.5.76 13.6.76 28.6.76 10.7.76 28.7.76 10.8.76 24.8.76 4.10.76 20.10.76 23.11.76 22.12.76 18.1.77  SECCHI DEPTH AND SURFACE AND SUBSURFACE SALINITY AND TEMPERATURE MEASUREMENTS MARCH 1976 TO JANUARY 1977  Secchi Depth (meters)  5.25 6.75 5.40 5.25 3.25 3.30 1.80 1.60 2.30 2.00 2.30 2.30 2.90 2.60 1.80 1.60 2.90 4.10 4.10 5.40  S a l i n i t y (parts per thousand)  (1.5 m)  Tenperature (°C)  Surface  1.5 m  Surface  1.5 m  26.0  10.5  28.5  8.0  27.2  9.0  27.6  9.0  28.0 26.3 24.0 22.7 22.5 22.8 19.9 13.8 20.1 22.9 21.4 22.5 26.5  11.0 11.6 11.8 15.5 15.0 17.5 17.0 16.0 11.2 10.3 8.0 8.2 8.0  28.0 27.0 24.3 23.7 23.5 24.0 21.2 18.2 26.2 23.8 30.0 27.6 26.0  10.5 10.8 11.9 14.3 14.0 16.0 15.0 14.8 10.8 10.4 7.8 8.6 8.0  APPENDIX 2: DIURNAL SURFACE AND SUBSURFACE (1.5 m) SALINITY (PARTS PER THOUSAND) MEASUREMENTS. MAY 2, JULY 28 AND OCTOBER 4, 1976. JANUARY 18, 1977.  Time (PDST)  May 2 1.5 m  Surface  26.3  26.3  21.8  26.3  26.3  Surface  0000 01.00 02.00 03.00 04.00 05.00 06.00 07.00 08.00 09.00 10.00 11.00 12.00 13.00 14.00 15.00 16.00 17.00 18.00 19.00 20.00 21.00 22.00 23.00 24.00  J u l y 28  October 4 1.5 m  23.2  Surface  1.5 m .  15.7  19.3  15.5  22.0  18.0  19.2  24.2  24.2  23.8  25.1  19.5  22.5  24.0  25.0  22.9  26.0  24.0  25.8  23.7  24.2  20.8  25.2  20.1  26.2  24.0  24.7  24.0  24.7  20.4  22.5  24.7  25.0  22.8  24.0  21.2  22.3  23.6  23.5  20.8  22.2  21.8  24.7  23.5  24.6  22.2  23.8  21.75  23.8  24.0  26.0  24.2  27.2  20.5  21.9  24.0  21.5  23.0  21.3  20.4  24.0  23.8  26.5  21.0  20.2  January 18 Surface  1.5 r  24.2  24.3  27.2  27.2  26.5  26.0  27.2  27.2  27.0  27.3  27.2  27.5  27.2  27.3  26.8  26.8  APPENDIX 3: DIURNAL AIR, SURFACE AND SUBSURFACE -(1.5 m) TEMPERATURE (°C) MEASUREMENTS MAY 2, JULY 28 AND OCTOBER 4, 1976. JANUARY 18, 1977.  May 2  Time  oooo 01.00 02.00 03.00 04.00 05.00 06.00 07.00 08.00 09.00 10.00 11.00 12.00 13.00 14.00 15.00 16.00 17.00 18.00 19.00 20.00 21.00 22.00 23.00 24.00  J u l y 28  October 4  January 18  Surface  1.5 m  Surface  1.5 m  Air  Surface  1.5 m  Air  12.5  12.5  14.5  13.8  16.3  10.4  10.8  9.5  12.5  12.5  10.0  11.5  10.4  10.0  10.8  9.0  11.0  11.0  13.4  12.8  14.2  10.1  11.0  9.2  11.0  11.5  14.75  12.25 20.5  10.8  11.0  9.8  11.33  11.5  17.0  14.0  26.25  11.2  10.8  10.8  11.5  11.75  16.0  14.0  23.0  11.8  .10.3  14.1  11.6  12.0  17.5  16.0  20.0  12.6  11.8  14.5  11.75  12.0  15.3  14.8  18.2  12.5  11.2  14.8  11.5  11.25  14.8  13.8  17.2  12.1  11.5  12.5  11.0  10.5  14.8  12.6  15.8  12.5  12.1  11.8  11.5  15.0  14.8  16.0  11.8  12.2  12.9  12.0  15.0  12.5  15.9  11.5  11.8  12.9  Surface  • 1.5 m  Air  7.5  7.5  14.0  8.0  8.0  12.0  7.6  7.6  7.5  8.0  8.0  9.6  8.2  8.1  12.9  8.2  8.0  10.6  8.0  7.9  8.2  7.8  7.8  8.2  7.8  7.8  8.0  95  APPENDIX 4: DIURNAL SECCHI DEPTH AND PHOTOSYNTHETICALLY ACTIVE RADIATION (PAR) MEASUREMENTS MAY 2, JULY 23 AND OCTOBER 4, 1976. JANUARY 18, 1977.  Time (PDST)  Secchi Depth (meters)  PAR Quanta (microeinsteins per square meter per second) 10 cm Above Surface  Surface  1.5 m  May 2 06.00 08.00 10.00 12.00 14.00 16.00 18.00 20.00  2.1 2.1 2.2 2.2 2.2 1.0 1.8 2.2  J u l y 28 06.00 08.00 10.00 12.00 14.00 16.00 18.00 20.00  3.1 3.9 3.5 2.8 2.9 1.5 2.1 2.75  170 1200 1900 2200 2500 310 250 150  45 500 1100 1450 1600 170 150 33  19 200 550 650 800 53 80 17  October 4 08.00 10.00 12.00 14.00 16.00 18.00  2.2 1.6 1.8 2.4 2.4 2.5  114 500 2150 2100 2000 500  64 220 975 1050 850 90  27 44 325 450 275 29  January 18 11.00 13.00 15.00 17.00  5.7 5.4 5.2 5.2  30 49 180 150 195 350 100 12  7 12 42 23.5 52.5 78 35 3  APPENDIX 5: NET OSCILLATIONS OF SEDIMENT SURFACE LEVELS MEASUREMENTS AND STATISTICS. JUNE 1976 TO JANUARY 1977  Date  11.8.76  26.8.76  14  9  15  9.64  9.36  9.29  9.83  10.10  10.90  11.74  -11.87  +0.36  +0.64  +0.71  +0.17  -0.10  -0.90  -1.74  -1.87  Standard Deviation  2.04  1.21  0.65  1.38  1.41  1.71  1.76  1.92  Standard E r r o r  0.59  0.32  0.22  0.36  0.32  0.42  0.51  0.55  Number o f Observations Mean height (cm) of pegs above sediment surface  s  Net change  30.6.76 20  10.00  29.7.76 12  4.10.76  20.10.76  23.11.76  22.12.76  19  17  12  19.1.77 12  vo  APPENDIX 6: STATISTICS OF STANDING CROP INFORMATION (ORGANIC DRY WEIGHT PER QUADRAT) USED FOR OPTIMUM QUADRAT SIZE DETERMINATION  Quadrat Area  Number o f Quadrats  1.0 m2  4  1 m x 1 m  0.5  8  0.71 m x 0.71 m  Quadrat Dimensions  Mean (g)  SD (g)  SE (g)  16.69  4.45  2.22  13.33  0.27  12.21  4.08  1.44  11.82  0.33  Percentage SE  CV.  0.25  12  0.5 m x 0.5 m  5.53  1.25  0.36  0.04  25  0.2 m x 0.2 m  0.81  0.46  0.09  11.22  0.56  0.01  50  0.1 m x 0.1 m  0.20  0.37  0.05  26.98  1.90  6.52  0.22  APPENDIX 7 : ORGANIC DRY WEIGHTS IN GRAMS PER SQUARE METER FOR FIVE ELEVATIONS (CHART DATUM) APRIL 1 9 7 6 to JANUARY 1 9 7 7 . 0.8  Date Apr.  6  m  0.3  Mean SE 9.91  Date Apr.  17  6  16.32  May  14  22.02  May  30  13.68  May  3  42.43  May  14  49.98  May  31  32.01  June 2 7  16.05  July 1 0  16.30  July 28  17.72  2.14  Aug.  25  13.03  25  Nov.  23  14.21  41.22  Aug.  25  20.22  Oct.  4  11.35  20  11.93  18  10.46 1.51  14  50.29  May  31.  49.47  Oct.  20  Nov.  23  11.23  Dec.  20  14.14  16.84  June  12  38.61  July  2  46.91  July  10  88.40  1.54  19  July  29  15.02 49.52  Aug.  26  35.69  Oct.  4  20.48  37.31  May  15  53.41  May  31  61.81  23  17.59  DGC •  22  10.46  13  55.67  July  2  37.07  July  10  59.38  7.00 1.72  3  17.93  May  15  12.43  May  31  38.45  9.82 5.19  July  28  7.38  June 1 3  22.35 6.85  July 3  2.17  26.12  10  53.23  Aug.  25  43.44  Oct.  4  32.23  2.90 31.68  Aug.  25  18.81  Oct.  4  17.10  Oct.  20  12.04  Nov.  23  16.10  Dec.  22  4.79 9.51  2.90 17.46  Nov.  23  14.97  DGC •  22  11.65  1.64  3.41  5.12  2.99  3.32  2.29  Jan.  19  20.52 3.24  8.82  10  8.77  20  38.42  Aug.  8.09  Oct.  12.69  11.22  July 2 8  11.15  Aug.  .  4.43  July 1 0  17.05  1.90 19  6.80  May  9.35  3.38  Jan.  30.30  11.44  June  5 . 2 6 .'  Nov.  19  8.60  3.23 10.62  Apr.  1.77  6.88  20  33.33  3  4.01  Oct.  Mean SE  34.67  May  7.43 10  Date  4.37  23.74  Aug.  m  -1.2  5.08  5.63  2.12 12.23  Apr.  9.14  0.87  18  6  9.32  3.88  Jan.  Apr.  11.86  >  m Mean SE  3.84  3.31  2.46  Jan.  May  3.66  1.80  Dec.  33.60  4.36  1.74 9.57  41.12  10  2.07  Oct.  47.44  Aug.  2.14 14.19  3  4.22  1.40  Sept. 2 8  47.97  36.78  May  17.93  July 2 9  3.58 16.16  57.26  Date  8.82  15.16  July 1 0  2.43  7  19  10.91  July 2  3.05  Aug.  Apr.  ,  4.83  June 1 2  43.37  -0.7  3.82  9.13  1.90 18.67  6  5.43  4.17  m Mean SE  4.41  2.63  June 1 2  Apr.  43.25 33.0  3.31 2  Date  3.77  18.61  May  -0.2  Mean SE  2.27  Apr.  m  3.68 1.25  Jan.  19  11.90 3.73  APPENDIX 8: ANALYSIS OF VARIANCE SUMMARY TABLE FOR MEAN LEAF STANDING CROP (ORGANIC DRY WEIGHT IN GRAMS PER 0.25 SQUARE METER QUADRAT) Source o f V a r i a t i o n Total  SS 8,170.13  DF  MS  Calculated F  Critical F  Conclusion  299  Elevation (A)  1,465.82  4  366.45  16.55**  FO.Ol(l),4,70 =' 3.60  Reject HQ  Time (B)  2,592.68  14  185.19  8.36**  FO.Ol(l),14,70 = 2.34  Reject HQ  . 1,415.65  56  22.14  3.21**  FO.Ol(l),70,140 = 1-60  Reject HQ  A x B  1,660.57  75  25.28  l-14ns  FO.Ol(l),50,70 = 1-83  Accept HQ  Error  1,035.41  150  6.90  Location (C)  VD VD  APPENDIX 9:  DENSITY IN TURIONS PER SQUARE METER FOR FIVE ELEVATIONS (CHART DATUM) APRIL 1976 TO JANUARY 1977  0.8 m  0.3 m  Date  Mean SE  Apr. 6  43 9.84  Date Apr. 6 Apr. 9  May 2 May 14 May 30 June 12 June 27 J u l y 10 J u l y 28 Aug. 7 Aug. 25 Sept. 28 Oct. 25 Nov. 23 Dec. 20 Jan. 18  36 .2.05 63 3.74 53 1.54 61 1.85 67 2.51 66 2.80 79 2.06 79 1.30 51 2.14 53 2.07 51 1.71 43 1.68 42 1.58 42 1.48  May 3 May 14 May 31 June 12 July 2 J u l y 10 J u l y 29 Aug. 10 Aug. 25 Oct. 4 Oct. 20 Nov. 23 Dec. 20 Jan. 18  Mean SE 89 3.77 66 1.56 95 3.30 106 ' 5.39 71 3.35 107 3.64 82 0.96 70 4.74 86 3.57 87 2.28 44 1.78 39 2.56 38 1.85 37 1.03 43 1.75 58 3.86  -0. 2 m Date Mean SE Apr. 6  May 3 May 14 May 31 June 13 July 2 J u l y 10 J u l y 29 Aug. 10 Aug. 26 Oct. 4 Oct. 26 Nov. 23 Dec. 22 Jan. 19  86 0.86  83 2.56 123 5.35 105 5.94 86 2.10 66 1.04 133 6.05 29 1.44 72 0.42 73 3.28 44 2.49 27 3.30 46 1.66 34 0.65 25 1.11  -0. 7 m  Date  Mean SE  -1.2 m Date  Mean SE  Apr. 6  119 4.07 Apr. 19 106 2.47 May 3 81 3.09 May 15 123 2.87 May 31 134 4.52 June 13 110 2.26 July 2 67 1.38 J u l y 10 93 7.19 J u l y 28 49 1.44 Aug. 10 94 3.28 Aug. 25 81 3.09 62 Oct. 4 1.19 Oct. 20 43 2.14 Nov. 23 48 1.36 Doc• 22 _ 42 1.85 Jan. 19 58 1.76  Apr. 19 May 3 May 15 May 31 June 13 July 3 J u l y 10 J u l y 28 Aug. 10 Aug. 25 Oct. 4 Oct. 20 Nov. 23 Dec. 22 Jan. 19  64 2.80 43 5.72 36 3.49 77 3.38 44 2.35 35 3.40 55 3.64 27 2.25 47 1.11 33 3.68 40 2.28 33 2.75 35 0.86 14 1.19 37 0.86  APPENDIX 10:  Source o f V a r i a t i o n  Total  ANALYSIS OF VARIANCE SUMMARY TABLE FOR MEAN TURION DENSITY (TURIONS PER 0.25 SQUARE METER QUADRAT)  SS  DF  MS  Calculated F  Critical F  Conclusion  21,287.43  279  Elevation (A)  3,128.41  4  782.10  13.52**  F  0.01(l),4,70  Time (B)  6,462.38  13  497.11  8.59**  F  0.01(l),13,70 = 2.40  Reject HQ  Location (C)  4,050.25  70  57.86  2.345**  F  0.01(l),70,140 =1-60  Reject HQ  A x B  4,191.89  52  80.61  1.393  F  0.01(l) ,50,70 = L 8 3  Accept HQ  Error  3,454.50  140  24.67  ns  = 3  6 0  Reject HQ  102  APPENDIX 11 : REPrClDUCITVE TURION DENSITY (PER SQUARE METER) FOR FIVE ELEVATIONS. JUNE TO AUGUST, 1976.  E l e v a t i o n (m) Date May 14, 15  0.8  0.3  -0.2  -0.7  -1.2  3 106 2.83  0 123 0  0 123 0  0 36 0  Reproductive Total % Reproductive  0 71 0  May 30,31  Reproductive Total % Reproductive  1 51 1.96  0 71 0  2 105 1.90  1 134 0.75  0 77 0  June 12, 13  Reproductive Total % Reproductive  5 91 5.49  3 107 2.80  0 86 0  1 110 0.91  0 44 0  J u l y 2, 3  Reproductive Total % Reproductive  0 100 0  2 82 2.44  4 66 6.06  0 67 0  3 35 8.57  J u l y 10  Reproductive Total % Reproductive  0 70 0  2 70 2.86  3 133 2.26  0 93 0  0 55 0  J u l y ,28, 29  Reproductive Total % Reproductive  0 69 0  2 86 2.33  0 29 0  2 49 4.08  0 27 0  August 7  Reproductive Total % Reproductive  0 79 0  0 87 0  0 72 0  0 94 0  0 47 0  -  N  APPENDIX 12: ANALYSIS OF VARIANCE SUMMARY FOR SLOPES OF THE REGRESSIONS OF TURION NUMBERS ON ORGANIC DRY WEIGHT FOR FIVE ELEVATIONS (CHART DATUM)  Elevation (meters) 0.8  0.3  -0.2  -0.7 ~  -1.2  Number o f Observations 88  64  62  64  60  Source o f Variation  SS  DF  MS  Calculated F  Total Linear Regression Residual  224.74 127.76 96.98  87 1 86  127.76 1.13  113.30  6.96  Reject B Q - . B = 0  Total Linear Regression Residual  1643.43 1056.68 586.75  63 1 62  1056.68 9.46  111.66  7.08  Reject HQ:P = 0  Total Linear Regression Residual  2481.98 1992.71 489.28  61 1 60  1992.71 8.15  244.36  7.08  Reject HQ: P = 0  Total Linear Regression Residual  1636.33 1111.82 524.51  63 1 62  1111.82 8.46  131.42  7.08  Reject HQ:£ = 0  Total Linear Regression Residual .  841.38 658.55 182.83  59 1 58  658.55 3.15  208.92  7.08  Reject EQ-.P = 0  F  0.01(l),l,n-2  Conclusion  I—  1  o co  104  APPENDIX 13.: MEAN BIOMASS OF INTERTIDAL (0.8 m) EELGRASS IN GRAMS PER SQUARE METER (ORGANIC DRY WEIGHT) . APRIL 1976 TO JANUARY 1977.  Leaves Date 16.4.76 15.5.76 12.6.76 10.7.76 7.8.76 24.8.76 25.10.76 23.11.76 17.1.77  Mean 28.80 16.98 27.45 25.33 7.90 10.68 10.64 10.10 9.29  Roots  Rhizomes  SE  Mean  SE  0.25 1.18 1.64 2.62 1.84 0.68 3.77 1.82 1.58  4.36 1.80 3.70 3.09 1.00 1.76 1.05 0.97 1.30  0.20 0.15 1.18 0.24 0.24 0.29 0.47 0.21 0.23  Mean 13.37 4.58 9.69 10.91 9.85 9.01 7.27 10.29 6.95  SE 0.26 0.34 1.88 1.84 1.85 2.29 2.93 1.76 1.21  

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