Bantam Lake Cyanos Activity July 13, 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 Monday, July 13th , AER visited Bantam Lake to perform Cyanobacteria and water quality monitoring. Water column profile data, total depth measurements, and Secchi transparency data 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).
An approximately 500mL composite sample of the top three meters of water column were collected for algae counts at the North Bay and Center Lake Sites using a threemeter long sampling tube. These samples were preserved with Lugol’s solution shortly after collection and stored at 3°C. Sample preparations and counting methods were undertaken as described in earlier memos. A concentrated plankton tow sample using a 10µm mesh plankton net was also collected at the Center Lake site. The concentrated plankton sample was transferred into a 25mL glass amber bottle, stored at 3°C, and preserved with Lugols after an examination with microscopy.
Secchi transparency measurements at all sites on July 13th were between 2.38 and 2.55 meters (Table 1). These measurements followed an approximate total of ¾ inches of rain during the prior three days, so transparency may have also been influenced by inorganic materials (e.g. sands, silts, clays). Nonetheless, these measurements were consistent with transparency measurements taken since June 17th (Fig. 1).
The lake average relative phycocyanin concentration in the top 3m of the July 13th water column was generally consistent with averages since June 17th with some minor fluctuation on July 1st (Fig. 2). Phycocyanin is the signature photosynthetic pigment of freshwater Cyanobacteria, a surrogate measurement of the relative amount of Cyanobacteria at those depths, and was measured in situ with a fluorimeter.
Cyanobacteria cell concentrations have gradually decreased since July 1st (Fig. 3). On July 13th , concentrations at the North Bay and Center Lake Sites were 15,561 and 12,854 cells/mL, respectively and represented an average 50% decrease over the averaged concentrations in the prior week (Fig. 3). The recent cell concentrations were within the Visual Rank Category 1 range (CT DPH & CT DEEP 2019). In the State’s Guidance to Local Health Departments for Blue–Green Algae Blooms in Recreational Freshwaters, interventions are not recommended at public beach sites for Category 1.
Dolichospermum spp. was the most abundant Cyanobacteria genus for the first time this season. This represents a shift in the pelagic algal community from being dominated by Aphanizomenon spp., as it has been since the June 1st Cyanobacteria bloom. Both genera exist as linear arrangements of cells in a filament. However, the Aphanizomenon spp. cells are smaller. This means the number of cells in a filament of Aphanizomenon spp. is greater than the number of cells in a filament of Dolichospermum spp. of the same length.
The decrease in Aphanizomenon spp. on July 13th was one reason for the decrease in the total Cyanobacteria cell concentrations in samples. Cells concentrations for this genus decreased from an average of 20,000 cells/mL on July 6th to an average of 2,700 cells/mL on July 13th, while Dolichospermum spp. cell concentrations were between 7,500 and 9,500 cells/mL on both dates regardless of site.
Aphanizomenon spp. and Dolichospermum spp. were two of seven Cyanobacteria genera observed in July 13th samples (Table 1). Those two genera plus several others observed are considered toxigenic (Cheung et.al. 2013, CT DPH & CT DEEP 2019, iNaturalist 2020).
Last week we described elevated relative concentrations of phycocyanin at a depth of 5m in the water column, particularly at the North Bay and Folly Point Sites, based on the July 6th profiles (Fig. 4a). The same types of elevated levels were not observed in the July 13th profiles (Fig. 4b).
Surface water temperatures on July 13th were similar to those measured on July 6th , while temperatures at the bottom of the water column on July 13th were slightly higher. The July 13th water column was stratified at all sites except the South Bay Site. The thermocline was located between 4 and 5m of depth at the North Bay and Folly Point Sites; and located between 5 and 6m of depth at the Center Lake Site. Oxygen concentrations at the three stratified sites were <1mg/L near the bottom of the water column (Table 2).
Literature Cited
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
[CT DPH & CT DEEP] 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
iNaturalist. 2019. Woronichinia. See https://www.inaturalist.org/guide_taxa/700578
Data is collected and analyzed by Aquatic Ecosystem Research who is contracted by Bantam Lake Protective Association.
On Monday, July 13th , AER visited Bantam Lake to perform Cyanobacteria and water quality monitoring. Water column profile data, total depth measurements, and Secchi transparency data 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).
An approximately 500mL composite sample of the top three meters of water column were collected for algae counts at the North Bay and Center Lake Sites using a threemeter long sampling tube. These samples were preserved with Lugol’s solution shortly after collection and stored at 3°C. Sample preparations and counting methods were undertaken as described in earlier memos. A concentrated plankton tow sample using a 10µm mesh plankton net was also collected at the Center Lake site. The concentrated plankton sample was transferred into a 25mL glass amber bottle, stored at 3°C, and preserved with Lugols after an examination with microscopy.
Secchi transparency measurements at all sites on July 13th were between 2.38 and 2.55 meters (Table 1). These measurements followed an approximate total of ¾ inches of rain during the prior three days, so transparency may have also been influenced by inorganic materials (e.g. sands, silts, clays). Nonetheless, these measurements were consistent with transparency measurements taken since June 17th (Fig. 1).
The lake average relative phycocyanin concentration in the top 3m of the July 13th water column was generally consistent with averages since June 17th with some minor fluctuation on July 1st (Fig. 2). Phycocyanin is the signature photosynthetic pigment of freshwater Cyanobacteria, a surrogate measurement of the relative amount of Cyanobacteria at those depths, and was measured in situ with a fluorimeter.
Cyanobacteria cell concentrations have gradually decreased since July 1st (Fig. 3). On July 13th , concentrations at the North Bay and Center Lake Sites were 15,561 and 12,854 cells/mL, respectively and represented an average 50% decrease over the averaged concentrations in the prior week (Fig. 3). The recent cell concentrations were within the Visual Rank Category 1 range (CT DPH & CT DEEP 2019). In the State’s Guidance to Local Health Departments for Blue–Green Algae Blooms in Recreational Freshwaters, interventions are not recommended at public beach sites for Category 1.
Dolichospermum spp. was the most abundant Cyanobacteria genus for the first time this season. This represents a shift in the pelagic algal community from being dominated by Aphanizomenon spp., as it has been since the June 1st Cyanobacteria bloom. Both genera exist as linear arrangements of cells in a filament. However, the Aphanizomenon spp. cells are smaller. This means the number of cells in a filament of Aphanizomenon spp. is greater than the number of cells in a filament of Dolichospermum spp. of the same length.
The decrease in Aphanizomenon spp. on July 13th was one reason for the decrease in the total Cyanobacteria cell concentrations in samples. Cells concentrations for this genus decreased from an average of 20,000 cells/mL on July 6th to an average of 2,700 cells/mL on July 13th, while Dolichospermum spp. cell concentrations were between 7,500 and 9,500 cells/mL on both dates regardless of site.
Aphanizomenon spp. and Dolichospermum spp. were two of seven Cyanobacteria genera observed in July 13th samples (Table 1). Those two genera plus several others observed are considered toxigenic (Cheung et.al. 2013, CT DPH & CT DEEP 2019, iNaturalist 2020).
Last week we described elevated relative concentrations of phycocyanin at a depth of 5m in the water column, particularly at the North Bay and Folly Point Sites, based on the July 6th profiles (Fig. 4a). The same types of elevated levels were not observed in the July 13th profiles (Fig. 4b).
Surface water temperatures on July 13th were similar to those measured on July 6th , while temperatures at the bottom of the water column on July 13th were slightly higher. The July 13th water column was stratified at all sites except the South Bay Site. The thermocline was located between 4 and 5m of depth at the North Bay and Folly Point Sites; and located between 5 and 6m of depth at the Center Lake Site. Oxygen concentrations at the three stratified sites were <1mg/L near the bottom of the water column (Table 2).
Literature Cited
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
[CT DPH & CT DEEP] 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
iNaturalist. 2019. Woronichinia. See https://www.inaturalist.org/guide_taxa/700578
Data is collected and analyzed by Aquatic Ecosystem Research who is contracted by Bantam Lake Protective Association.
