Phytoplankton activity in the Red and Assiniboine rivers as they flow through the City of Winnipeg, Manitoba

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Goodman, Leslie G.
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Phytoplankton activity in the Red and Assiniboine Rivers was examined during the ice-free period over two years (1994 and 1995) to evaluate the impact of physical and chemical factors (including) anthropogenic discharges on phytoplankton productivity, photosynthesis and standing crop. In total, approximately 60 kms of the Red and Assiniboine Rivers were sampled on a weekly basis for phytoplankton activity and this was related to the physico-chemical status in the Rivers by a series of multivariate approaches including principal component, canonical correlation and multiple discriminant analyses. The spatio-temporal variability in parameters was examined and pronounced temporal fluctuations in parameters appeared to be highly correlated with River flow rate. Between Rivers and between upstream and downstream Red River locations, there were significant differences in primary productivity that were related to the availability of light within the water column (i.e., euphotic depth) and possibly to nutrient load. The study clearly identified the restrictions of phytoplankton saturated production to the superficial layers of the water column. While light extinctions were significantly different between years of the study, there was an alteration in phytoplankton photosynthetic efficiency that is proposed to have sustained a conservative saturating depth for photosynthesis. The differences in turbidity between 1994 and 1995 in the Red River did not reduce saturated photosynthesis but rather compromised light-limited rates in 1994. (Abstract shortened by UMI.)