Cyanos Activity May 22, 2018

Water is clean for recreation.

Disclaimer: The information presented below reflects conditions throughout the lake and may differ from conditions on specific shorelines. For information regarding beach closings please contact the Torrington Area Health District or local town officials.

The concentration of Cyanobacteria cells increased compared to those enumerated from the May 8th samples. Dolichospermum spp. (formerly Anabaena spp.), Woronichinia spp., Coelosphaerium spp., and Microcystis spp. were observed in the live and preserved net tow samples during this sampling event. At the North Bay Site, Dolichospermum spp. was the only genus encountered; that genera was found at a concentration of 324 cells/mL and 8% of the total planktonic algal community. Uroglenopsis spp. and Dinobryon spp. of the golden algae taxa collectively comprised 83% of the total 4,031 cells/mL at that site, which suggests that this site’s community is still dominated by Chrysophytes. 

At the Center Lake site, the cyanobacteria were more prominent and comprised 40% of the planktonic algal community; that group was largely represented by Dolichospermum spp. However, the golden algae genus Uroglenopsis spp. comprised 46% of the community. Diatoms collectively accounted for about 12% of the community. Total cell concentrations at the Center Lake Site was 3,967 cells/mL. These data suggest that the planktonic community is becoming more productive at the Center Lake site and that the blue-green algae group is increasing in productivity as well. 

Secchi transparency was good; it ranged from 3.42 to 3.56m with a four-site average of 3.50m. 

Surface water temperatures on May 21st increased from approximately 16 to 18°C between May 8th and this sampling event. Surface water temperatures during this 2 sampling event ranged between 15.8 to 16.7°C. However, temperatures at the bottom (based on sites with >6m depth) increased by approximately 1°C since May 21st . 

Stratification and increased resistance to mix between lake layers contributed to lower oxygen levels below 5m. Oxygen concentrations >10mg/L from the surface to a depth of 4m. At depths of 5m, oxygen concentrations were between 7 and 10mg/L. Below the 5m stratum, oxygen concentrations ranged from 2.6 to 1.3mg/L. This strongly differs from that observed on May 8th when >8mg/L was observed at the bottom of all four sites and suggests that benthic microbial activity’s demand for oxygen is surpassing the refresh rate from the surface due to mixing. Stratification is playing a significant role in thwarting the redistribution of oxygen from the surface to the bottom; AER would anticipate that nutrients are loading from the sediments and will continue to do so as the oxygen concentrations continue to decline.

Data is collected and analyzed by Aquatic Ecosystem Research, who is contracted by Bantam Lake Protective Association.

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