Overview of Recreational Season for 2023

By David Ernes – Lake Management Committee

The 2023 season turned out to be a season of unusual weather coupled with unexpected observations. Despite this, for the third straight year, we ended the season with no algal toxin levels exceeding the EPA Advisory limit. We also added over 400 pounds of feeder fish to enhance the excellent fishery. This document includes a review of the issues we faced and the conclusions from the reports from our consultants.

The report from EnviroScience related to the in-lake conditions found that, on a whole lake basis, the algaecide treatments were successful at maintaining the recreational use of the lake. Selected areas did observe issues but overall, the lake has seen an improvement since 2021. In August, algae populations increased primarily in the north, which was surprising, prompting the second partial algaecide treatment. The nitrogen levels were elevated above that seen in prior years. The report does encourage efforts being done to control the nutrients by seeking financial assistance.

The AquaDoc report, measuring the conditions south of the lake, showed phosphorus levels similar to last year. The increase in nitrogen levels primarily for nitrate, appeared at the end of June and originated in Whetstone Creek. It appeared as the weather shifted from a drought to heavy rain events. It slowly returned to normal as the summer progressed. While the source is unknown, the elevated nitrogen level is felt to be responsible for some of the unusual observations this season.

Throughout the course of the year, we have been in communication with our consultants to try to understand the unusual situations we experienced. The consensus opinions are briefly described below.

Filamentous Algal Mats. As has been discussed both at Board Meetings and e-blasts, an increase in non-toxic green, filamentous algae is expected as we work to control the more toxic blue-green algae. In addition, the increase in nitrogen (in the form of nitrates) entering the lake likely acted as a ‘fertilizer’ for the filamentous algae, increasing the magnitude of the problem, especially in the south.

Floating snails. At the end of June, an increased number of floating snails were observed. These snails, likely Mystery Snails, are invasive to our area. They seemed to originate in the south (observations in September found them to proliferate south of the lake) with the shells floating north with the current. The complicating factor is that these snails can float and still be alive. Observations by our consultants and the author have confirmed this. While there are several possibilities to explain why they behaved as they did, it is not clear which factor (or some combination of factors) was responsible. The fact that this was unique to this season suggests the nitrate level increase as a likely contributing factor.

Odor in the South.  Around September 22, a sewer-like odor was observed in the south end of the lake, extending upstream of the bridge. This was found to be due to a condition called hypoxia, where the oxygen level in the lake was depleted. When this happens, odor-causing chemicals are released as the aquatic vegetation and algae die off at that time of year, consuming dissolved oxygen in the water. Normally the fall rain brings in freshly oxygenated water, but the unusually dry September prevented this, so the normal processes occurring in the lake were again disturbed. In addition, the high level of filamentous algae, and the excessive vegetation in the lake below Spanish Cove and extending south of the Route 6 bridge added to the load. This drop in oxygen also adversely affected the fish (and snail) population in this area. With artificial aeration and returning rainfall, the situation was corrected.

Overall, this year we saw that factors beyond our control acted against our efforts to improve conditions in the lake. Until we find a Bond villain with a weather control machine, we will have to do our best to adapt. As in the past, we will use lessons learned this season to direct our plans moving forward. Because, as always, we all must do our best to…

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