Cyanos Activity May 5, 2019

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.

On Monday, May 6, 2019, AER visited Bantam Lake to conduct biweekly cyanobacteria monitoring as part of the ongoing lake management program. Water column profile data and Secchi transparencies were collected from the North Bay Site (N 41.71087° W -73.21155°), the Center Lake Site (N 41.70056° W -73.22102°), a site west of Folly Point (N 41.70773 W -73.22638), and at a site in the South Bay region of the lake (N 41.69015 W -73.22728). 

Samples for algal identifications and enumerations were collected from the North Bay and Center Lake sites. A plankton net tow sample using a 10µm mesh net was collected at the Center Lake site. Samples were treated, stored and analyzed following methods discussed in our April 30th memo. 

A total of nineteen algal genera were observed in the net tow and integrated water samples. The golden algae (Chrysophyta) and diatoms (Bacillariophyta) were the most diverse groups being represented by four and six genera, respectively. The filamentous cyanobacteria Aphanizomenon spp., was observed again at the North Bay site but was not nearly as abundant compared to April 22nd . Pseudoanabaena spp. was also observed at both sites but only comprised 28 and 1% of the total cells at the North Bay and Center Lake sites, respectively. 

Total cell concentrations were 1,437 and 1,632 cells/mL at the North Bay and Center Lake sites, respectively; an order of magnitude lower than that observed on April 22nd . The cyanobacteria were found at concentrations of 514 and 4cells/mL at the North Bay and Center Lake sites, respectively. The most abundant taxon was the golden algae, which comprised 47 and 90% of the algal community at North Bay and Center Lake sites. The most abundant golden alga was Uroglenopsis spp. 

Average Secchi transparency improved by almost 1 meter since April 22nd. Measurements ranged from a high of 3.50m at the North Bay site to a low of 2.69m at the South Bay site (Table 1); the lake-wide average was 3.00m.  

The water column was still mixed at all four sites, but May 5th surface temperatures were about 1°C warmer than those encountered on April 22nd at all but the North Bay site while bottom temperature changed much less over that period of time. This suggests the process of stratification had started but temperature/density gradients were no sufficient to create true stratification. Despite that, there was a notable loss of oxygen at the bottom of all sites except the North Bay site. This was most distinctive at the Center Lake and South Bay sites.

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