 the summertime fish kills given the right sequence of weather events. In this case, extreme heat and sunshine earlier that week at the reservoir likely contributed to a large algae bloom that subsequently died during the cooler temperatures and cloud cover that happened in the days that followed. Now, when algae die, the bacteria that consumes it also consumes oxygen. When the algae die off as excessive, it can cause fish kills, and that's exactly what happened in this 77-acre lake.