The lake has gone through its Fall Turnover meaning the temperature stratification that was a summertime feature of the lake has broken down and the lake water has mixed pretty much from top to bottom. The high winds from the remnants of Hurricane Lee last a week ago Saturday certainly helped with the mixing! Kelsie French and I were out doing our biweekly water quality monitoring last Friday and the water temperature at the surface (21.5°C) was only 2.5°C warmer than the water 8m (26ft) down. Two weeks ago the temperature difference from top to bottom was 7.8°C.

That turnover resulted in Phosphorus-rich water at the bottom of the lake mixing with the upper sunlit layers, giving a shot of nutrients to the cyanobacteria living there. A week later, they’re beginning to die off and float to the surface resulting in that telltale green scum on the water surface. The picture at left was sent to me by Jack Holland. Yesterday morning the green stuff was fairly evident over much of the lake surface (featured image, above), thanks to the lack of wind. It quickly dissipated when the wind picked up.

While no algae bloom is a good thing, as blooms go this one is pretty mild and it was expected.  Hopefully it won’t get much worse. Last fall you may recall we experienced a much worse bloom, way more intense and widespread that  went on for 3 months, extending all the way through November. It is likely all the rain we had this summer and the resulting flushing action that kept our water quality so high for so long.