401 Webbs Mills Road, Raymond, Maine 04071 - Tel: 207-655-4742 Fax: 207-655-3024


Lake Auburn Fish Kill

Could It Happen Here?

 

From Charlie Turner:

Hi all; 

      I attended the Coordinators Meeting of the VLMP last Saturday and learned a few things that should concern us in Raymond regarding our lakes. As you know, there was a large fish kill in Lake Auburn over the summer, and, in talking with Scott Williams, learned the probable cause. This is important, as the same thing COULD happen here. So here it is.
 
       The ice went out quite early, due to the mild winter. This made it possible for the sun to start warming the lake up earlier. Then, the summer proved to be quite warmer (hotter) than usual heating the lake to record high temps. This drove the cold water fish to deeper levels. So far, so good. BUT, the lower levels of the lake lose their oxygen gradually (which does not get replaced due to the thermocline, which acts as a barrier). So the fish were dealt a double whammy. They couldn't survive the shallower waters because they were too warm, and they couldn't survive at the deeper levels because there wasn't enough oxygen to breathe. So, they died. This phenomenon could happen anywhere, yes, even in Raymond. Below is a quick summary of the three layers of a lake so as to make things clearer.
 
 
       hyperlimnion (upper levels) ----------the layer near the surface to around 15-25 feet down. This is the place where most of the flora and fauna live, with good mixing of currents and sunshine, replenishment of oxygen, etc.
 
       thermocline  (middle level) ----------- a layer of rapid temp change, often around a degree per foot, seldom thicker than 10 feet. This characteristic effectively seals off the top from the bottom
 
        hypolimnion (bottom level)------------ this lowest layer becomes quite stagnant, with little mixing or sunlight. As the summer progresses the oxygen is gradually used up from bacteria and bottom sediments, and does not get replenished until either the spring or fall turnover.  Temps change very little over the whole year.
 
            Hope this has been helpful.  

            Cheers,

                 Charlie

 

Follow-up from Scott Williams of VLMP:

     This is a good summary, Charlie.  The only thing that I would add is that the early ice-out in march resulted in a significantly longer period of thermal stratification last summer, the effect of which was profound. The hypolimnion was isolated from the atmosphere for a longer period of time than has been typical historically.  As a result, dissolved oxygen levels below the bottom of the epilimnion were virtually depleted by early September, when we started to observe dying lake trout.

     Thanks for helping to get the word out.  We will be publishing an article about Lake Auburn in the upcoming edition of our newsletter.

      Scott

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