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UBC Theses and Dissertations

The effect of current on natural periphyton communities Oguss, Emily


The effect of current on loss rates of periphyton tissue was studied in three different flow-controlled streams in British Columbia. Artificial substrates were exposed to constant currents ranging from 3.0 to 121.8 cm./sec. Indigenous periphyton species which colonized the substrates were labeled with inorganic P³³, and the loss of the label monitored for up to 46 days. Daily loss rates were calculated from these data. Graphing the daily loss rates against currents indicated a sigmoid relationship: very little effect of currents less than 20 cm./sec.; sharply increasing effect of currents between 20 and 80 cm./sec.; and a leveling off above 80 cm./sec. This model fits all three streams despite their many differences and is therefore interpreted as a general model of current effects on periphyton loss rates in natural streams. The component of loss due to invertebrate grazing is discussed. A computer simulation model of periphyton dynamics was used to compare different theories about other aspects of periphyton dynamics. This model differs from previous periphyton models in several important ways: (1) up to three algal species can be handled separately, rather than grouping all periphyton into one "quasi-organism", (2) changing colony morphology was used as a factor, (3) emphasis was put on the realism of each dynamic relationship rather than on mimicking total biomass data from specific streams. Three questions that are presently unsolved about periphyton dynamics are examined using the computer simulation program, and tentative answers are arrived at. A complete listing of the program plus the parameter list is included in the Appendixes.

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