State of the Lake 2019

Aquatic Ecosystem Research

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The following is a bulleted outline of findings from the 2019 water quality monitoring program at Lake Wononscopomuc.

By October 2nd, concentrations of <1mg/L had extended up to a depth of 13m from the surface, which was over half of the total water column.

o At Site 2 (17m deep), concentrations of <1mg/L were also first observed on June 12th from the 14m stratum to the bottom.

Concentrations of <1mg/L were also observed at 13m of depth to the bottom on July 9th and at 12m of depth to the bottom on September 3rd and October 2nd.


o Epilimnetic total phosphorus concentrations were between 6 and 15µg/L all season; the averages at Sites 1 and 2 were 10 and 11µg/L, respectively. However, phosphorus was non-detectable during several months.

o Epilimnetic total nitrogen was generally low throughout the season. Average concentrations were 260 and 240µg/L at Sites 1 and 2, respectively, with actual concentrations measured between 140 and 300µg/L. In some months, nitrogen concentrations were below detectable levels.

The largest constituent of total nitrogen in the hypolimnion was ammonia.


Because of the high alkalinity or buffering capacity, pH was very stable with epilimnetic measurements varying from only 8.7 to 8.9, and hypolimnetic measurements falling between 7.5 and 7.7.


o Average specific conductance at a depth of 1m of 284µS/cm in 2015 increased to 322µS/cm by 2019.

Increasing specific conductance is occurring in many lakes and has been associated with stormwater runoff containing deicing and other salts.

o The 2019 levels in the epilimnion decreased as the season progressed.

Levels increased in the hypolimnion after June 12th


Lowest ORP at the bottom of Site 1 occurred on October 2nd.

o At Site 2, lowest ORP was observed on July 9th and continued to be low enough for phosphorus loading through September 3rd; but, those low ORP levels were confined to the bottom 2m of the water column on July 9th and bottom 1m of the water column afterwards.


(e.g. diatoms, green algae, dinoflagellates) dominated or were co-dominant. o Highest concentrations of Cyanobacteria were not in the top 3m of the water column but were detected via fluorimetry below the lower boundary of the metalimnion throughout the season.


o Algal productivity based on cell counts, was low and may be due – in part – to coprecipitation with calcium and magnesium carbonates.

Figure 1. Regressions from ANOVA analyses of water quality variables that significantly changed between 2015 and 2019. Total Phos = total phosphorus, and TKN = Total Kjeldahl Nitrogen. Not pictured but significant was hypolimnetic alkalinity.