Cyanos Activity June 23, 2021

 

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.

Introduction and Methods

AER visited Bantam Lake to conduct biweekly Cyanobacteria monitoring and monthly water quality monitoring as part of the Bantam Lake Protective Association’s ongoing lake management efforts. Data collected in the field included measurements of temperature, dissolved oxygen, specific conductance, and pH at one-meter intervals from the top to the bottom of the water column, total depth, and Secchi disk transparency. These data were collected at four sites: 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). 

A plankton net tow sample using a 10µm mesh plankton net was collected at the Center Lake site. Approximately 500 mL from the top three meters of the water column were integrated and collected for algae counts at the North Bay and Center Lake sites using a three-meter-long sampling tube. These samples were preserved with Lugol’s solution shortly after collection and stored at 3 C. Samples were also collected in a similar fashion for analysis of microcystin toxins in the laboratory of Dr. Edwin Wong at Western Connecticut State University. Methods for analyses of the phytoplankton net sample and the integrated samples discussed in our April 30th memo were followed.

Water Clarity

Water clarity on June 23rd was notably good with readings at three sites measured between 3.70 and 3.97 meters (Table 1). This represents an approximately 1 meter increase in clarity since June 8th. At the South Bay site, Secchi transparency was 2.87m and similar to that measured at the South that site on June 8th .

Algae Community and Cyanobacteria Cell Concentrations

Thirty (30) algal genera were observed in the net tow and integrated whole water samples. The Cyanobacteria (aka Blue-green Algae) and Chlorophyta (aka Green Algae) constituted 9 and 13 of the total genera observed, respectively. The remaining eight genera were divided among six taxonomic groups. 

The Cyanobacteria cell concentrations decreased since June 2nd when concentrations were between 24,000 and 29,000 cells/mL and reflective of Visual Rank Category 2 conditions (CT DPH and CT DEEP). The recent Cyanobacteria cell concentrations were between 15,000 and 16,000 cells/mL and characteristic of Visual Rank Category 1 conditions (Table 1).

The dominant Cyanobacteria genus continued to be Aphanizomenon spp. (Fig. 1a). The second most important Cyanobacteria genus was Dolichospermum spp. (Fig. 1b). Others included Microcystis spp. (Fig. 1c), Aphanocapsa spp. and Woronichinia spp. These species are listed in the literature as toxigenic (Cheung et. al. 2013, CT DPH & CT DEEP 2019, EPA 2020).

Water Column Temperature and Oxygen Characteristics

Water temperatures near the surface were between 22.2 and 22.7°C (Table 1), which were 1 to 2°C lower than those recorded on June 8th . All sites but the South Bay site were stratified with a thermocline located between 4 and 5m of depth; resistance to mixing at the thermocline was considered strong (RTRM >80). Oxygen concentrations at the bottom of the water column at those sites were <1mg/L (Table 1). At the mixed South Bay site, the oxygen concentration at the bottom of the water column was 7.9mg/L.

Literature Cited

Connecticut Department of Public Health and Connecticut Department of Energy and Environmental Protection [CT DPH & CT DEEP]. 2019. Guidance to Local Health Departments for Blue–Green Algae Blooms in Recreational Freshwaters. See https://portal.ct.gov/-/media/Departments-and-Agencies/DPH/dph/environmental_health/BEACH/Blue-Green-AlgaeBlooms_June2019_FINAL.pdf?la=en 

Cheung MY, S Liang, and J Lee. 2013. Toxin-producing Cyanobacteria in Freshwater: A Review of the Problems, Impact on Drinking Water Safety, and Efforts for Protecting Public Health. Journal of Microbiology (2013) Vol. 51, No. 1, pp. 1–10. See http://www.jlakes.org/ch/web/s12275-013-2549-3.pdf 

United States Environmental Protection Agency [US EPA]. 2020. Health Effects from Cyanotoxins. https://www.epa.gov/cyanohabs/health-effects-cyanotoxins 

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