Cyanos Activity June 4, 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 06/04/2019 AER visited Bantam Lake to conduct biweekly cyanobacteria monitoring as part of the ongoing lake management program. Water column profile 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).
Samples collected for algal identifications and enumerations were from the North Bay and Center Lake sites. A plankton net tow sample, using a 10µm mesh plankton net, was collected at the Center Lake site. Samples were treated, stored and analyzed following methods discussed in previous memos.
Average Secchi transparency was 4.27m; approximately 1m greater than that observed on May 22nd. North Bay and Center Lake Secchi transparencies were 4.86 and 4.95m, respectively, which were the highest recorded at any site since April of 2018. The Folly Point and South Bay sites had Secchi transparencies of 4.09 and 3.18m, respectively which were good for Bantam Lake but were notably lower that observed at the North Bay and Center Lake sites.
A total of 29 algal genera were observed in the tow sample and integrated water samples used for counts. Green algae (Chlorophyta) and cyanobacteria were the most diverse taxa with 9 and 8 genera, respectively. Five genera of diatoms (Bacillariophyta) were also identified.
Concurrent with the high Secchi transparencies were low algal cell concentrations, including cyanobacteria. Total cell concentrations were 548 and 1,338 cells/mL at the North Bay and Center Lake sites, respectively which were similar to total cell concentrations in samples collected on May 22nd . The cyanobacteria cell concentrations were 281 cells/mL (51% of the total cells) and 551 cells/mL (41% of the total cells) at the North Bay and Center Lake sites, respectively and also similar to those encountered on May 22nd .
As noted above, cyanobacteria comprised between 41 and 51% of the planktonic algal community. Cells of the cyanobacteria genera Aphanizomenon spp., Dolichospermum spp., and Woronichinia spp. were the most numerous. Diatoms cells constituted 14 and 43% of the pelagic community at the North Bay and Center Lake sites, respectively. The difference in diatom abundance between the two sites was due to the filamentous diatom Aulocoseria spp. which constituted 24% of all cells counted at the Center Lake site. The colonial diatom Asterionella spp. was an important community member at both sample sites. Golden algae (Chrysophyta) were also important and comprised 24 and 14% of the total cells at the North Bay and Center Lake sites, respectively. Important golden algae genera included Synura spp., Mallomonas spp., and Uroglenopsis spp.
Surface water temperatures continued to climb and were approximately 3°C warmer than those measured on May 22nd . Temperature changes near the bottom over the last two weeks were modestly less. The water column was stratified at three sites with a thermocline observed between 4 and 5m at the North Bay site and between 5 and 6m at the Center Lake and Folly Point sites. The water column at the South Bay site remained mixed.
Oxygen concentrations were >8.0mg/L throughout much of the water column across the lake. However, oxygen concentrations at 0.5m above the sediment / water interface were 0.0mg/L at North Bay, Center Lake, and South Bay sites, and 0.5mg/L at the Folly Point site.
Data is collected and analyzed by Aquatic Ecosystem Research, who is contracted by Bantam Lake Protective Association.
Samples collected for algal identifications and enumerations were from the North Bay and Center Lake sites. A plankton net tow sample, using a 10µm mesh plankton net, was collected at the Center Lake site. Samples were treated, stored and analyzed following methods discussed in previous memos.
Average Secchi transparency was 4.27m; approximately 1m greater than that observed on May 22nd. North Bay and Center Lake Secchi transparencies were 4.86 and 4.95m, respectively, which were the highest recorded at any site since April of 2018. The Folly Point and South Bay sites had Secchi transparencies of 4.09 and 3.18m, respectively which were good for Bantam Lake but were notably lower that observed at the North Bay and Center Lake sites.
A total of 29 algal genera were observed in the tow sample and integrated water samples used for counts. Green algae (Chlorophyta) and cyanobacteria were the most diverse taxa with 9 and 8 genera, respectively. Five genera of diatoms (Bacillariophyta) were also identified.
Concurrent with the high Secchi transparencies were low algal cell concentrations, including cyanobacteria. Total cell concentrations were 548 and 1,338 cells/mL at the North Bay and Center Lake sites, respectively which were similar to total cell concentrations in samples collected on May 22nd . The cyanobacteria cell concentrations were 281 cells/mL (51% of the total cells) and 551 cells/mL (41% of the total cells) at the North Bay and Center Lake sites, respectively and also similar to those encountered on May 22nd .
As noted above, cyanobacteria comprised between 41 and 51% of the planktonic algal community. Cells of the cyanobacteria genera Aphanizomenon spp., Dolichospermum spp., and Woronichinia spp. were the most numerous. Diatoms cells constituted 14 and 43% of the pelagic community at the North Bay and Center Lake sites, respectively. The difference in diatom abundance between the two sites was due to the filamentous diatom Aulocoseria spp. which constituted 24% of all cells counted at the Center Lake site. The colonial diatom Asterionella spp. was an important community member at both sample sites. Golden algae (Chrysophyta) were also important and comprised 24 and 14% of the total cells at the North Bay and Center Lake sites, respectively. Important golden algae genera included Synura spp., Mallomonas spp., and Uroglenopsis spp.
Surface water temperatures continued to climb and were approximately 3°C warmer than those measured on May 22nd . Temperature changes near the bottom over the last two weeks were modestly less. The water column was stratified at three sites with a thermocline observed between 4 and 5m at the North Bay site and between 5 and 6m at the Center Lake and Folly Point sites. The water column at the South Bay site remained mixed.
Oxygen concentrations were >8.0mg/L throughout much of the water column across the lake. However, oxygen concentrations at 0.5m above the sediment / water interface were 0.0mg/L at North Bay, Center Lake, and South Bay sites, and 0.5mg/L at the Folly Point site.
Data is collected and analyzed by Aquatic Ecosystem Research, who is contracted by Bantam Lake Protective Association.
