CS16 Harmful Algal Blooms
Date: Wednesday, June 12, 2002
Location: Poster Session - VCC
FindlayDL, Fisheries and Oceans, Freshwater Institute, Winnipeg, Canada, findlayd@dfo-mpo.gc.ca
Paterson, M, J, Fisheries and Oceans, Freshwater Institute, Winnipeg, Canada, patersonm@dfo-mpo.gc.ca
Kling, H, J, Algal Taxonomy and Ecology Inc., Winnipeg, Canada, hkling@mts.net
Reports of Gonyostomum semen blooms have increased over the past decade. It has been identified in small lakes, flooded reservoirs, and drinking water retention ponds in Europe and North America. In many Scandinavian lakes mass blooms of this species have been associated with water quality and health problems, with reports of skin lesions from bathers. Several hypotheses have been advanced concerning factors favoring the dominance of G. semen. These include the influence of pH, nutrients, and changes in food web structure. We examined these relationships in two experimentally flooded reservoirs (L979 and Res2) at the Experimental Lakes Area (ELA northwestern Ontario) where G. semen reached maximum biomasses of 15 g m-3. Concentrations of major nutrients increased in both reservoirs following flooding. pH decreased from 6.5 to 5.5 in L979 but was relatively stable in Res2 (6.0). Both reservoirs experienced large increases in Daphnia. The abundance of G. semen was negatively correlated with the abundance of Daphnia. We concluded changes in food web structure influenced increased abundances of G. semen in these flooded reservoirs.