Kirsten, some microbial metabolism does occur at low temperatures. That is why there is sometimes oxygen depletion in winter, under ice. When ice cover occurs, gas exchange with the atmosphere is obviously precluded. Under ice metabolism has been sufficient to deplete oxygen enough to cause fish deaths.
That said, Occam's razor serves me in the instance you speak of. We are experiencing exceptionally warm winters in recent years (even while we do have some extremes like the -32 F recorded in Oklahoma a couple of years ago, and the current bout of brutally cold weather across the northern U.S. states and much of Canada east of the Rockies). Why would your unfrozen or thinly frozen lake not be a part of the general phenomenon of warmer than normal winters? This is a pattern, not limited to certain geographic regions. It has been exceptionally warm for the past few years, and this winter is no exception to that. David McNeely ---- Kirsten Harma <kharm...@yahoo.com> wrote: > In my corner of eastern British Columbia we've h > Greetings Ecologists, In my corner of eastern British Columbia we've had a warmer than average winter and a later than average date of freeze of our local lake (surface freezes completely, usually thick enough to drive on). Yet no one talks of "climate change," rather, some people have been attributing the thin ice to decaying aquatic plants. I assume this is because gases as a byproduct of decay bubble up, bringing +4 water to the surface-- but would decay be happening during the winter? We have a pretty shallow lake (maximum depth = 7 metres; average = 3 metres) and we haven't recorded thermal stratification in our lake in the spring, summer or fall. I would like to educate the community about how much of an influence decaying plants might be having on creating thin sections of ice on the lake. I would appreciate hearing your ideas on the impacts of decaying plants on ice melt and their possible relative contribution to thin ice. Thanks so much! ~Kirsten Harma, MSc. Invermere, BC (my apologies for the repost -- the first posting appeared with a very strange format on Ecolog) -- David McNeely
