Despite the improvement in water quality recently, we are still continuing to monitor the algal toxin microcystin in North Pond, now with the help of volunteers from the North Pond Association. Last Thursday, we still detected no microcystin in the lake and we will continue to monitor through September.
Because of the cooler windier weather, we are cautiously optimistic that we might not have another bloom this year. But we still need to be vigilant! Before the alum treatment, East Pond regularly bloomed in September. Our most recent measurements from last Thursday show a lake that is still on the edge. The Secchi disk transparency has improved to 8 ft, but by comparison Little North has visibility all the way to the bottom in the middle of the basin, and East Pond is twice that at 16 ft. The phosphorus in North Pond is still above 15 ppb, which is relatively high for the Belgrade Lakes and also means there is still fuel for algae growth.
The 7 Lakes Alliance has updated our water quality equipment and we are now able to measure chlorophyll when we do our water quality profiles. Like plants on land, algae also use chlorophyll for photosynthesis. So by measuring chlorophyll in the water, we can get a relative approximation for how much algae is in the water. North Pond currently has 15 ug/L of chlorophyll throughout the water column, which is more than 10 times as much as in Little North and the other lakes!
We will be analyzing an algae sample at the 7 Lakes Alliance this week to determine if the algae in the water is cyanobacteria or possible diatoms and golden algae, which start growing when the weather gets cooler (and which are much less likely to produce any sort of toxin).
So while North Pond has cleared up quite a bit in the last few weeks, the summer is not yet over for the algae! 7 Lakes Alliance, Colby College, and the North Pond Association are working together to keep an eye on the situation as the summer winds down! Remember to report any algal scums on your shoreline here, so that we can target our monitoring!