Cyanos Activity August 12, 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 August 12th AER visited Bantam Lake to perform monthly water quality monitoring and cyanobacteria monitoring as part of the ongoing lake management program. Samples collected for algal identifications and enumerations were from the North Bay site (N 41.71087° W -73.21155°) and Center Lake site (N 41.70056° W -73.22102°). A plankton net tow sample, using a 10µm mesh plankton net, was also collected at the Center Lake site. Samples were treated, stored, and analyzed following methods discussed in a previous memo.
Water column profile and Secchi transparency data were also collected at the North Bay Site, the Center Lake Site, as well as at 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).
Conditions since our August 1st visit continued to be generally good. Average Secchi transparency on August 12th was 3.02m and only moderately lower than the average of 3.43m on August 1st. The difference was largely due to the lowest Secchi transparency on August 12th measured at the North Bay site which was 0.78 to 1m less than those measured at the other sites (Table 1).
The North Bay site is always the first of the four sites we visit. Wind conditions on August 12th were very calm upon arrival at approximately 8:15 AM and while in route to the North Bay site once on the lake. We noted what appeared to be light algal bloom conditions near the Center Lake site while traveling to the North Bay site. During our time at the North Bay site, winds picked up and a light breeze persisted for the remainder of time at the lake. Secchi transparencies measured at all sites, under the light breeze conditions, ranged from 3.12 to 3.34m.
Cyanobacteria can become positively buoyant at night and under calm conditions come to the surface and form a bloom. Mixing due to the wind can redistribute the cyanobacteria, as can changes in cell buoyancy. It is unclear why Secchi transparency at the North Bay site was lower than those at the other sites, but relative cyanobacteria profile data collected with the fluorimeter on the field instrumentation sensor array corroborate the differences (Fig. 1). Relative cyanobacteria measurements in the top 4 meters of the water column at North Bay were greater that those at the other three sites.
Since August 1st cyanobacteria cell concentrations have remained relatively low at both the North Bay and Center Lake sites. Cell concentrations in samples collected on August 12th do not warrant any interventions based on the State guidance (CT DPH & CT DEEP 2019). August 12th cyanobacteria cells comprised 81 and 77% of the algal cells counted in North Bay and Center Lake site samples, respectively. Important cyanobacteria genera include Aphanocapsa spp. and/or Aphanothece spp., Coelosphaerium spp., Dolichospermum spp., and Pseudoanabaena spp.
Water temperatures at the surface on August 12th were several less than those measured on August 1st. The water column at the Center Lake site was still stratified with the upper warmer layer separated from cooler water below starting between 5 and 6 meters. Some stratification was observed at the bottom of the Folly Point site and the North Bay site to a lesser degree. The South Bay site was mixed. Resultingly, oxygen concentrations at the bottom of North Bay, Center Lake, and Folly Point were ≤0.02mg/L while 7.1mg/L at South Bay.
Literature Cited
Connecticut Department of Public Health and Connecticut Department of Energy andEnvironmental Protection. 2019. Guidance to Local Health Departments For Blue–Green Algae Blooms in Recreational Freshwaters.
Data is collected and analyzed by Aquatic Ecosystem Research, who is contracted by Bantam Lake Protective Association.
On August 12th AER visited Bantam Lake to perform monthly water quality monitoring and cyanobacteria monitoring as part of the ongoing lake management program. Samples collected for algal identifications and enumerations were from the North Bay site (N 41.71087° W -73.21155°) and Center Lake site (N 41.70056° W -73.22102°). A plankton net tow sample, using a 10µm mesh plankton net, was also collected at the Center Lake site. Samples were treated, stored, and analyzed following methods discussed in a previous memo.
Water column profile and Secchi transparency data were also collected at the North Bay Site, the Center Lake Site, as well as at 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).
Conditions since our August 1st visit continued to be generally good. Average Secchi transparency on August 12th was 3.02m and only moderately lower than the average of 3.43m on August 1st. The difference was largely due to the lowest Secchi transparency on August 12th measured at the North Bay site which was 0.78 to 1m less than those measured at the other sites (Table 1).
The North Bay site is always the first of the four sites we visit. Wind conditions on August 12th were very calm upon arrival at approximately 8:15 AM and while in route to the North Bay site once on the lake. We noted what appeared to be light algal bloom conditions near the Center Lake site while traveling to the North Bay site. During our time at the North Bay site, winds picked up and a light breeze persisted for the remainder of time at the lake. Secchi transparencies measured at all sites, under the light breeze conditions, ranged from 3.12 to 3.34m.
Cyanobacteria can become positively buoyant at night and under calm conditions come to the surface and form a bloom. Mixing due to the wind can redistribute the cyanobacteria, as can changes in cell buoyancy. It is unclear why Secchi transparency at the North Bay site was lower than those at the other sites, but relative cyanobacteria profile data collected with the fluorimeter on the field instrumentation sensor array corroborate the differences (Fig. 1). Relative cyanobacteria measurements in the top 4 meters of the water column at North Bay were greater that those at the other three sites.
Since August 1st cyanobacteria cell concentrations have remained relatively low at both the North Bay and Center Lake sites. Cell concentrations in samples collected on August 12th do not warrant any interventions based on the State guidance (CT DPH & CT DEEP 2019). August 12th cyanobacteria cells comprised 81 and 77% of the algal cells counted in North Bay and Center Lake site samples, respectively. Important cyanobacteria genera include Aphanocapsa spp. and/or Aphanothece spp., Coelosphaerium spp., Dolichospermum spp., and Pseudoanabaena spp.
Water temperatures at the surface on August 12th were several less than those measured on August 1st. The water column at the Center Lake site was still stratified with the upper warmer layer separated from cooler water below starting between 5 and 6 meters. Some stratification was observed at the bottom of the Folly Point site and the North Bay site to a lesser degree. The South Bay site was mixed. Resultingly, oxygen concentrations at the bottom of North Bay, Center Lake, and Folly Point were ≤0.02mg/L while 7.1mg/L at South Bay.
Literature Cited
Connecticut Department of Public Health and Connecticut Department of Energy andEnvironmental Protection. 2019. Guidance to Local Health Departments For Blue–Green Algae Blooms in Recreational Freshwaters.
Data is collected and analyzed by Aquatic Ecosystem Research, who is contracted by Bantam Lake Protective Association.
