Cyanos Activity April 26, 2022
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, April 26th, AER visited Bantam Lake to conduct biweekly cyanobacteria monitoring as part of the ongoing lake management program. 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).
A plankton tow sample using a 10μm mesh plankton net was collected at the site. The concentrated plankton sample was transferred into a 25mL glass amber bottle and stored at 3°C. Approximately one liter of the top three meters of water column was in-tegrated and collected for algae counts at both the North Bay and Center Lake sites using a three-meter-long sampling tube. Those samples were preserved with Lugol’s solution shortly after collection and stored at 3C.
A portion of the live phytoplankton in the net sample was carefully examined with mi-croscopy on the same day it was collected to identify and list all algal genera present prior to any treatment or preservation. Afterwards, the net sample was preserved with Lugol’s Solution and stored. The integrated whole water samples were prepared and analyzed as described in our April 15, 2022 memo.
Cyanobacteria and Algae Community
A total of 22 algae genera were observed among the net tow and concentrated whole water samples. Seven of those genera were from the Cyanophyta (aka cyanobacteria or blue-green algae), five genera were from the Chlorophyta (aka green algae), and three genera from each of the Bacillariophyta (aka diatoms) and Chrysophyta (aka golden algae) were observed. Several other algae taxonomic groups were represented by one or two genera.
Total algae cell concentrations were 6,891 and 6,855 at the North Bay and Center Lake
sites, respectively. Golden algae constituted approximately 62% of all cells at both
sites. The dominant genus was the colonial Uroglenopsis spp. (Figs. 1a, 1b). Other
golden algae genera counted included Mallomonas spp. (Fig. 1c) and Synura spp.
Cyanobacteria cell concentrations were low at both sites: 2,440 cells/mL at the North
Bay site and 2,468 cells/mL at the Center Lake site. These concentrations were characteristic
of Visual Rank Category 1 (or good conditions) according to Connecticut’s
guidance for municipalities (CT DPH & CT DEEP 2019) and were consistent with our
visual assessment of conditions (see below). Aphanizomenon spp. (Fig. 1d) and
Planktothrix spp. were equally important at both sites. A long filament of Lyngbya spp.
was also observed at the North Bay site.
Conditions
The skies were very overcast and mist conditions were encountered for much of the
morning of April 26th. Nonetheless, Secchi disk transparencies were good and between
3.52 and 3.83 meters among the four sites (Table 1).
The water columns at all four sites were thermally mixed with the exception of very
bottom of the North Bay site where a thermocline was detected between the 5- and 6-
meter strata. Surface water temperatures were between 11.1 and 12.1°C (52 and 53.8°F)
while temperatures near the bottom were between 10.3 and 10.5°C (50.5 and 50.9°F).
Oxygen concentrations were high throughout the water columns of all four sites (Table
1).
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-
Data is collected and analyzed by Aquatic Ecosystem Research who is contracted by Bantam Lake Protective Association.
