Thursday, May 29, 2008 - 4:00 PM
619

Effects of nutrients on sestonic algae, benthic algae and macrophytes in streams

Chantal Vis, Parks Canada, 111 Water Street East, Cornwall, ON K6H 6S3, Canada and Patricia Chambers, Environment Canada, Burlington, ON L7R 4A6, Canada.

The response of sestonic and benthic algae and submerged macrophyte communities to nutrients (phosphorus and nitrogen) was compared for streams and rivers in Ontario and Quebec to better understand eutrophication of running waters.  Based on data from the literature and provincial monitoring programs, we found differing responses amongst aquatic plant communities to increasing streamwater concentrations of total phosphorus (TP) and total nitrogen (TN).  Sestonic algal biomass increased with nutrient concentration (TP and TN), and the slope of the relationship was influenced by catchment area.  Benthic algal biomass showed a weak curvilinear relationship with TP, yet a continually increasing response to TN.  In contrast, macrophyte communities had no significant relationship with either streamwater nutrients, but biomass increased with catchment area.  Analysis of relationships between biomass and streamwater N:P ratios showed opposite trends for sestonic and benthic algae: sestonic algal biomass was more strongly controlled by P whereas benthic algae biomass was mainly driven by N, except when P concentrations were low (< 12 µg/L).  Results suggest that both TP and TN concentrations are important in predicting both the response of each type of primary producer to eutrophication and shifts in dominance amongst primary producers in running waters.


Web Page: aquatic plants, nitrogen, phosphorus

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