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Distribution and taxonomy of planktonic marine diatoms in the Strait of Georgia, B.C. Shim, Jae Hyung

Abstract

The primary objectives of this study were the identification and measurement of diatom genera and species making up the diatom communities in the plankton of the Strait of Georgia/Juan de Fuca Strait system, and factors influencing their distributional ecology. The planktonic diatom communities at depths of one, 25, 50, and 75 meters in the area were studied and measured over a fifteen month period. Measurements of environmental factors included temperature , salinity and algal nutrients such as phosphate, silicate, nitrate, nitrite and ammonia. Attempts were made to establish relationships between environmental factors measured and marine planktonic diatoms through the use of multiple regression analyses. The results indicate that the total abundances of diatom communities and the species population changes were strongly correlated with season and location parameters (in which the exact regulating parameters are unknown) as well as specific nutrient concentrations and hydrographic factors. Major influences on population distributions varied with the principal species responsible for the observed species successions. Two distinct distributional patterns in total diatom standing crop were observed in the study area. Maximum standing crops observed during spring and/or summer did not usually result in the depletion of critical nutrients (such as silicate, nitrate) to levels which might be growth limiting. In a few instances phosphorus concentration was undetectable. On a small scale, the distribution of total diatom standing crop was significantly correlated with both season/location factors and with hydrographic parameters. Vertical stratification of diatoms was observed only in the presence of the thermocline/halocline in the water column. The distribution of recurrent groups of diatoms was related primarily to the physical conditions. Within the study area there was some seasonal consistency in the composition of the species groups. There were radical changes in community structure with different seasons, as was expected. Two hundred and nineteen taxa have been identified as a results of light and scanning electron microscope observations. These taxa are attributed to 66 genera within 16 families. Of the total number of taxa three appear to be new species and five are new infraspecific taxa. Sixty-eight taxa are new records for western Canada. Some changes in the previous classification system were made using new information which has been accumulated through better technical facilities, especially through the scanning electron microscope. The diatom classification system used here was based on the present state of knowledege of diatoms and the author's own observations.

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