I would like to share some observations after the poisoning of Lake Maspenock that occurred in mid-June. The water birds left — swans, geese, eagles, heron, cormorant, ducks. They are slowly returning. The ducks came first. Around three weeks after the poisoning, our lake was covered in thousands of large and small smelly, dead snails. No swimming again in the upper basin. People, too, seem to be using the lake less in spite of the heat. There is less life here. There are fewer weeds now at the end of summer, so maybe some are pleased.
A little history: Around 1960, the lake was poisoned with dioxin for the weeds. This is a now-banned chemical that does not go away. Around 1980, it was poisoned with 24D, another banned chemical, also because people were annoyed with weeds. This time diquat was used, and it, too, is banned in many countries. I have heard that there will be testing of the water. The chemicals accumulate and persist in the lake bottom soil. To quote an old folk song, “When will we ever learn?”
— Carol Esler, Hopkinton
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The Health Director offers the following clarification.
During the week of the elevated snail mortality, the lake water temperature at Sandy Beach and in the shallow areas of the lake exceeded 80 F. The limnologist that assists the DPW and Lake Maspenock Preservation Association and Health Director believe that the high temperature and a corresponding decrease in the dissolved oxygen in the shallow waters of the lake is what contributed to the death of the snails. As the snails decomposed a further decrease in dissolved oxygen occurred in the shallow areas, likely contributing to the death of a small percentage of fish in the lake.
The Health Department collected two lakebed sediment samples from Lake Maspenock in the recent past and found no legacy pesticides in the samples collected. The Department intends to collect additional lakebed sediment samples and water samples this year for pesticide analysis.