Use of water clarity to monitor the effects of climate change and other stressors on oligotrophic lakes

We present evidence from studies of lakes in Killarney Park, Ontario. Canad a that water clarity is a key variable for monitoring the effects of climat e change, high UV exposure and acidification. In small oligotrophic lakes, these stressors affect water clarity primarily by altering the concentratio n of DOC in lake water. Clear lakes (<2 mg L-1 DOC) proved to be highly sen sitive indicators of stressors, exhibiting large thermal and optical respon ses to small changes in DOG. Extremely clear (<0.5 mg L-1 DOC) acidic lakes showed the effects of climate change and solar bleaching in recent decades . These lakes became much clearer even though they were slowly recovering f rom acidification.