I was at a lake in Me. that was on both sides of the road,,one side was green and the other was normal,,,why?

Question

The people I was with said it was not green 2 days before,,so why would it all of a sudden be green. Some said it was called dog days (when a lake overturns) the bottom comes to the top and the top goes to the bottom,,,can this be what happened?,,,I am very curious about this. Serious answers only please.

Answer 1

Sounds like a bloom of plants or algae.  They can happen suddenly for various reasons;  some run-off of fertilizer, or a change in the weather that the plants are triggered by, etc.  Sounds like the road is on a d**e that makes the lake two separate bodies of water, so the bloom wouldn't extend to both.

Answer 2

I was going to pooh-pooh the idea out of hand until it penetrated my thick skull that you are talking about Maine. Could the water be down to 40°F already? That's when you get an overturn. Because an overturn stirs up the bottom sediments, the phosphorus in those sediments fertilizes the water and you could get a bloom. If the other side were shallow, it might not overturn at all. Or it might not overturn if it were  deeper or were at a higher temperature.

The principle behind overturn is that water is densest at about 40°F. In the summer, warmer water is above the densest water. In the winter, colder water is above it. During the spring and fall, you get a switch-over, causing overturn.

Answer 3

Been getting alot of rain lately?   Someones septic tank overflowed and "fertilized" the lake.   Some of the old cabins might have a direct line to the lake still grandfathered in as gross as it might seem now.