The Influence of Heated Thermal Effluent on Life History Evolution in Mosquitofish

When generating electricity, many power plants emit heated thermal effluent into nearby aquatic environments.  One such example is the Big Brown Power Station in Freestone County, Texas.  This power plant emits thermal effluent into a contained ‘hot pond’ section of Lake Fairfield, Texas that elevates the temperature of the heated section by 9^oC over the lake proper.  Such elevated temperatures have potential to exert significant selection on the organisms found in the ‘hot pond’.  Yet, in general, the evolutionary consequences of heated thermal effluent are not well understood.  Here we performed a preliminary assessment of life history variation in mosquitofish (Gambusia affinis) from sites that are or not continually exposed to heated thermal effluent.  We performed monthly sampling of life history phenotypes over a several month period.  In this presentation, we will discuss differences in the size at maturation and investment in reproduction between fish found in the hot pond and lake proper sections of Lake Fairfield.