On the Algae in Joe's Pond

I have been on the Pond since 1945 and beleive this has happened every year. Old timers say it is the Pond turning over.If you have a thermometer in the pond you will notice that the temp drops when this happens and then warms up again. It seems to lay on the bottom in shallow areas until it lets loose or is distubed by boat traffic. I hope I am right in my observations. Ralph Hastings used to speak of this and I took him as somewhat of and authority on Joes Pond . Bryce Montgomery