Water temperature will be decreasing the next week as we see cloudy and cooler weather. Currently the lake is 77 degrees but with high temperature expected to be in the mid-70’s and lows around 60 this coming week the lake will continue to lose heat.
Water clarity increased dramatically from July 24 to August 2, which reflects the improvement brought on by the alum treatment. The benefit was short lived however since transparency has decreased since the treatment. Our August 29-30 treatment will increase clarity again, which will show up in our September 4 sampling.
Phytoplankton biovolume in Lakewood Bay has stayed the same from July 31 to August 14, but the percent cyanobacteria has increased. It is slightly more than 50% cyanobacteria currently, with the dominant species being Dolichospermum planktonica with Aphanizomenon flos-aquae coming in second. The total volume has decreased since the July 17 sample, and the concentration is not very high down in the water column, but as always with cyanobacteria the buoyancy tends to concentrate it at the surface at times.
Phytoplankton in the Main Lake has increased, with diatoms being the most numerous and making up 85% of the biomass and cyanobacteria only 11%. There is not one dominant cyanobacteria species in the Main Lake, with all five species present making up less than 100,000 µm3/mL each. You would think the concentration would be higher looking at the lake last weekend where cyanobacteria was forming surface films in some areas, but conditions differ from one location to another, and we always sample from the middle of the lake so we may not be capturing the worse conditions. In addition, cyanobacteria move around with the wind so downwind areas tend to have higher concentrations. I imagine our August 28 sample will show considerably more cyanobacteria but the alum application taking place August 29-30 will reduce phosphorus and drive down this current bloom.
West Bay is an amazing generator of diatoms, with a peak of over 25 million um^3/ml in late May. This will persist throughout the year with diatoms dominating, but at a reduced overall biovolume. As of August 14 there were 28 diatom species in West Bay, with the two larger species Fragilaria crotonensis and one of my favorites Stephanodiscus niagarae taking up a lot of the biovolume.