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State warns starry stonewort established in Lake Memphremagog; containment now focus
Summary
Vermont DEC officials told the Newport City Council that starry stonewort, a nonnative algae-like aquatic plant first confirmed in the lake in 2015, now occurs in multiple locations and that immediate containment and spread-prevention — not eradication — are the practical priorities.
Annie Bowe, an aquatic invasive‑species coordinator with the Vermont Department of Environmental Conservation’s Lakes and Ponds Section, told the Newport City Council on Oct. 17 that starry stonewort (a nonnative algae-like species) was first confirmed in Lake Memphremagog in 2015 and has since been found in additional sites including South Bay and a separate population in Derby Pond. “The Lake Memphremagog population found in 2015 was the first confirmation of this species in Vermont,” Bowe said.
Bowe said the species forms dense mats, produces bulbils that can germinate into new plants and can grow in a wide range of nutrient and depth conditions. She described Scotts Cove as heavily infested, estimating the plant covered most of the cove’s roughly 24 acres. “That wad that I'm passing around is basically just a garden rake full dipped into Scotts Cove,” she said, pointing to bulbils visible on a specimen she circulated.
The council heard that management options are limited. Bowe summarized two approaches used elsewhere: diver‑operated suction harvesting — effective only at very small scales and labor intensive — and chemical treatments, which present public‑health and permitting hurdles. “Chemicals are being used, but effectiveness are very limited,” she said, adding that state health officials must find any chemical mix presents negligible public‑health risk before a permit would issue.
Because eradication appears infeasible at the current densities, Bowe said the state is emphasizing spread prevention and monitoring. She described public‑access greeter and volunteer inspector programs, two portable decontamination units that can provide high‑pressure hot‑water rinses, and local signage and training as near‑term measures. “We now have portable decontamination units. We have two of them that rove around the state,” she said.
Valerie Dillon, identified as a trained Vermont invasive patroller who first alerted DEC staff to the Scotts Cove find, and representatives from the Memphremagog group in Quebec assisted DEC surveys; DEC found the lake’s larger populations at Scotts Cove and in South Bay but did not find starry stonewort in the Quebec portion of the lake during this sampling effort. Bowe said researchers are investigating likely pathways of introduction and spread — mud trapped on anchors and other equipment appears to be the most likely vector — and that genetics work is underway to trace the plant’s origins.
Bowe asked for local cooperation on spread prevention and monitoring, and said she hoped to work with the city on using DEC resources and volunteer programs in 2017. The state also held a temporary 90‑day closure of Scotts Cove in May 2016 to buy time for assessment, she said.
Why it matters: council members and residents asked about recreational and ecological impacts, and whether the species might displace Eurasian watermilfoil or otherwise harm fish spawning habitat. Bowe cautioned that many impacts are not yet fully understood at the site, and emphasized monitoring and public‑education measures while research continues.
The council did not take a formal vote on regulatory measures at the meeting; Bowe repeatedly urged enhanced volunteer greeter staffing, signage and use of decontamination units as the immediate next steps.
