Cyanos Activity April 13, 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 Wednesday, April 13th, AER visited Bantam Lake to conduct monthly water quality monitoring and biweekly cyanobacteria monitoring as part of the ongoing lake man-agement 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 Center Lake site. The concentrated plankton sample was transferred into a 25mL glass am-ber bottle and stored at 3°C. Approximately 1 liter of the top three meters of lake water were integrated and collected for algae counts at both the North Bay and Center Lake sites using a three-meter long sampling tube. These 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. Measured volumes of the whole water samples from the North Bay and Center Lake sites were treated with hydrostatic pressure to collapse gas vesicles within cyanobacteria cells. Measured volumes were then concentrated with a centrifuge and a vacuum filtration system. Portion of the concentrates were transferred to a counting chamber. Cells were identified to the genus level and enu-merated by counting cells in a randomized portion of the counting chamber with an in-verted Nikon Diaphot research microscope at a total magnification of 300X. Cell counts were then corrected to be representative of the whole water samples.
A total of 24 algal genera were observed among the net tow and concentrated whole water samples. Seven of those were genera from the Bacillariophyta (aka Diatoms); five genera of Cyanophyta (aka cyanobacteria or blue-green algae) and Chlorophyta (aka green algae) were identified; and three genera of Chrysophyta (aka golden algae) were identified. Other taxonomic group were represented by one or two genera. Although represented by few individual genera, the golden algae were nonetheless the
most abundant taxonomic group. The colonial golden algae Uroglenopsis spp. (Fig. 1a)
constituted 64% and 70% of all cells counted in the Center Lake and North Bay sites,
respectively. Other genera from the golden algae include the colonial Synura spp. and
the unicellular Mallomonas spp. (Fig. 1b).
The Cyanophyta comprised 28% and 34% of all cells counted at the North Bay and
Center Lake sites, respectively. The filamentous Aphanizomenon spp. was the most
abundant (Fig. 1c) followed by Planktothrix spp. (Fig. 1d). Cyanobacteria ell concentration
at the North Bay and Center Lake Sites were 2,813 and 5,147 cells/mL, respectively.
Both concentrations were below the intervention threshold of 20,000 cells/mL, and
indicative of Visual Rank Category 1 (CT DPH & CT DEEP 2019).
Surface water temperatures were between 9 and 10°C (48°F and 50°F). The water column
at all four sites was mixed, particularly at the Folly Point site (Table 1). Some disparity
in temperatures between the top and bottom strata were detected at the other
three sites meaning the water column was starting to stratify (Table 1) Oxygen concentrations
were good and >10mg/L at all depths. Secchi disk transparencies were
generally good with a low of 2.54m measured at the North Bay site, and a high of
3.00m measured at the Center Lake site.
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.
