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Re: NFC: Fw: Yes, please help me.

David A Zitnik wrote:
> This brings up an interesting question.  For my whole life, I assumed that
> deep water in lakes was a cool refuge for fish in the summer.  However,
> last semester, when I took limnology, I was taught that the deep wter in
> lakes (below the thermocline where it is cool) has virtually no oxygen.
> Lab testing backed this up.  So, according to this, a shallow lake would
> not be at a disadvantage to a deep lake in the summer.  In fact, when
> lakes turn over in spring and fall, deep lakes often experience fish kills
> due to the mixing of the oxygen-poor deep water with the rest of the lake.
> Now, I am far from an expert on this, so I will gladly accept
> comments/questions/criticizms.  What does everybody think?

This may be a problem for small lakes, but large deep lakes (such as
Lake Superior) are apparently well-oxygenated down to the bottom.  In
large lakes, mixing due to waves and currents may prevent oxygen
depletion in the lower levels.  Also, the Great Lakes are oligotrophic,
so there's relatively little organic matter to decay and consume oxygen.

Andrew Dalton