Cyanos Activity June 9, 2020
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 Tuesday, June 9, 2020, AER visited Bantam Lake to reassess the cyanobacteria bloom encountered on June 1st . 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).
Integrated water samples were collected at the North Bay and Center Lake Sites using a three-meter long sampling tube. Preparations of the samples for algae counts have been discussed in earlier memos (e.g. preserved with Lugols, hydrostatic pressure, concentration with centrifugation, etc.). A concentrated sample was collected with a 10µm mesh plankton net from the Center Lake Site.
Visual observations at the lake indicated that conditions were improved. Cyanobacteria cell concentrations at the North Bay and Center Lake sites were 9,188 and 8,163 cells/mL, respectively, and substantially lower than the 93,000 to 150,000 cells/mL determined from three samples collected on June 1 st . The State of Connecticut’s Guidance to Local Health Departments For Blue–Green Algae Blooms in Recreational Freshwaters (CT DPH and CT DEEP 2019) indicates that cyanobacteria cell concentrations of <20,000 cells/mL are characteristic of Visual Rank Category 1 conditions and do not warrant intervening actions in the interest of public health and safety.
Average Secchi transparency or water clarity on June 9th was approximately two times greater than that observed on June 1st . A lake average of 1.53 meters on June 1st improved to 3.15 meters on June 9th and was more consistent with readings prior to June 1 st (Fig. 1). An additional line of evidence supporting the improved conditions was the phycocyanin concentrations determined with the fluorimeter in AER’s field instrumentation. Phycocyanin is the photosynthetic pigment unique to the cyanobacteria. The lake average concentration on June 1 st was three to four times greater than concentrations measured on May 21st and June 9th (Fig. 2).
Although cell concentrations diminished since June 1st , cyanobacteria remained the dominant taxonomic group in the samples, comprising 87 and 93% of all cells counted at the North Bay and Center Lake Sites, respectively. As observed in June 1st samples, Aphanizomenon spp. was the dominant cyanobacteria genus. Other cyanobacteria genera observed included Aphanocapsa spp., Aphanothece spp., Dolichospermum spp., Coelosphaerium spp., Microcystis spp., and Woronichinia spp. A total of eight genera of Chlorophyta (aka Green algae) were also observed in the 25 total genera identified in June 9 th samples.
Surface water temperatures were just above 21°C (Table 1). The water column was stratified at all sites with the thermocline at North Bay, Center Lake, and Folly Point sites located between 4 and 5 meters of depth. Oxygen concentration below the thermocline at these sites diminished to below 0.5mg/L. At the South Bay site the thermocline was between 3 and 4 meters of depth. Oxygen levels at the bottom of the South Bay site were 3.3mg/L.
Literature Cited
Connecticut Department of Public Health and Connecticut Department of Energy and Environmental Protection. 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
Data is collected and analyzed by Aquatic Ecosystem Research who is contracted by Bantam Lake Protective Association.
On Tuesday, June 9, 2020, AER visited Bantam Lake to reassess the cyanobacteria bloom encountered on June 1st . 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).
Integrated water samples were collected at the North Bay and Center Lake Sites using a three-meter long sampling tube. Preparations of the samples for algae counts have been discussed in earlier memos (e.g. preserved with Lugols, hydrostatic pressure, concentration with centrifugation, etc.). A concentrated sample was collected with a 10µm mesh plankton net from the Center Lake Site.
Visual observations at the lake indicated that conditions were improved. Cyanobacteria cell concentrations at the North Bay and Center Lake sites were 9,188 and 8,163 cells/mL, respectively, and substantially lower than the 93,000 to 150,000 cells/mL determined from three samples collected on June 1 st . The State of Connecticut’s Guidance to Local Health Departments For Blue–Green Algae Blooms in Recreational Freshwaters (CT DPH and CT DEEP 2019) indicates that cyanobacteria cell concentrations of <20,000 cells/mL are characteristic of Visual Rank Category 1 conditions and do not warrant intervening actions in the interest of public health and safety.
Average Secchi transparency or water clarity on June 9th was approximately two times greater than that observed on June 1st . A lake average of 1.53 meters on June 1st improved to 3.15 meters on June 9th and was more consistent with readings prior to June 1 st (Fig. 1). An additional line of evidence supporting the improved conditions was the phycocyanin concentrations determined with the fluorimeter in AER’s field instrumentation. Phycocyanin is the photosynthetic pigment unique to the cyanobacteria. The lake average concentration on June 1 st was three to four times greater than concentrations measured on May 21st and June 9th (Fig. 2).
Although cell concentrations diminished since June 1st , cyanobacteria remained the dominant taxonomic group in the samples, comprising 87 and 93% of all cells counted at the North Bay and Center Lake Sites, respectively. As observed in June 1st samples, Aphanizomenon spp. was the dominant cyanobacteria genus. Other cyanobacteria genera observed included Aphanocapsa spp., Aphanothece spp., Dolichospermum spp., Coelosphaerium spp., Microcystis spp., and Woronichinia spp. A total of eight genera of Chlorophyta (aka Green algae) were also observed in the 25 total genera identified in June 9 th samples.
Surface water temperatures were just above 21°C (Table 1). The water column was stratified at all sites with the thermocline at North Bay, Center Lake, and Folly Point sites located between 4 and 5 meters of depth. Oxygen concentration below the thermocline at these sites diminished to below 0.5mg/L. At the South Bay site the thermocline was between 3 and 4 meters of depth. Oxygen levels at the bottom of the South Bay site were 3.3mg/L.
Literature Cited
Connecticut Department of Public Health and Connecticut Department of Energy and Environmental Protection. 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
Data is collected and analyzed by Aquatic Ecosystem Research who is contracted by Bantam Lake Protective Association.
