Major shifts in diatom community structure suggest the influence of recent climate change on lakes in the boreal region of Canada.

Wiltse B & Cumming BF. 2009. Major shifts in diatom community structure suggest the influence of recent climate change on lakes in the boreal region of Canada. Ontario Ecology and Ethology Colloquium, Queeen’s University, Kingston, ON Canada.

Various studies throughout North America have shown that ice-free periods of lakes are increasing. These changes have largely been attributed to a warming climate in these regions. The IPCC predicts that temperatures in North America will warm at a rate higher than the global mean. It has been suggested that the greatest degree of warming will be observed during the winter months, and that the snow and ice season will decrease with time. Previous studies at the Experimental Lakes Area (ELA) have shown large increases in planktonic diatoms over the past century. A similar trend has been observed in arctic lakes where warming is of a much higher magnitude. The most notable change has been in C. stelligera, which is a planktonic diatom that requires well stratified water columns. ELA lakes have been populated with C. stelligera for many centuries, although recently C. stelligera has started to increase in relative abundance. Previous work has shown widespread increases of C. stelligera over 20 ELA lakes, suggesting a regional forcing factor. It is believed that longer ice-free periods are allowing greater degrees of stratification which is favoring C. stelligera. We have looked at two lakes at ELA in much greater detail than previous studies. Two sediment cores were analyzed for changes in diatom community structure and dated using Pb-210 radioisotopes. We found a notable shift in the diatom community towards more planktonic forms; particularly C. stelligera. This suggests a major shift in the ecology of these lakes.