Meadowlark,

I'm convinced certain species of filamentous algae perfer colder water. Or unseasonibly cold temps followed by a quick warm up with wind could bring up nutrients from the bottom quickly and fire it up.

My trout pond has filamentous algae even in winter, and it becomes quite prolific around the edges into late spring. Then once early summer comes around it vanishes and the trout pond is dominated by chara. I think chara apparently has a competitive advantage in the slightly warmer water.

If pigs could fly bacon would be harder to come by and there would be a lot of damaged trees.