DANBURY, CONN. — Western Connecticut State University biologists have teamed up with local lake authorities, town governments, energy providers and community stakeholders to pursue field research that documents the rapid spread of invasive species in several major reservoirs in the region and broadens the base of scientific understanding to inform public policy action.

The primary focus of field and laboratory studies conducted since 2011 by WCSU researchers in the Department of Biological and Environmental Sciences has been the tracking of growth in recently established zebra mussel colonies in Lake Lillinonah and Lake Zoar, and the monitoring of Candlewood Lake for zebra mussel presence. The final report published in July 2015 offered clear statistical evidence of explosive growth in the zebra mussel populations in Lillinonah and Zoar during the past three years.

“Up to now, there is no evidence of zebra mussels in Candlewood Lake,” observed Dr. Mitch Wagener, WCSU professor of biological and environmental sciences and co-author of the report. “However, the populations of zebra mussels in Lillinonah and Zoar have grown exponentially.”

The report’s executive summary concluded that the high densities of adult and larval zebra mussels suggest that zooplankton and calcium levels are sufficiently high to permit successful and continuing zebra mussel reproduction in Lillinonah and Zoar. Similar nutrient and calcium conditions in Candlewood, the report noted, indicate that “the danger of future introduction is very real.”

Wagener said these findings underscore the need for heightened vigilance to prevent the spread of zebra mussels to Candlewood, and the urgency of addressing the significant challenges for recreational use, power generation and ecological balance at Lillinonah and Zoar as zebra mussel colonies continue to expand and coat surfaces ranging from boat hulls, docks and pipes to lake bottoms along the shoreline. Based on the experience of more mature colonies in other fresh-water locations in the eastern United States, he said, “it seems likely that the numbers in Lillinonah and Zoar will continue to go up and do considerable damage to the food webs in the lakes, before they finally crash and then level off at a new ‘normal.’”

Report co-author Dr. Edwin Wong, associate professor of biological and environmental sciences, has led another line of investigation to analyze DNA samples from zebra mussels present in Lillinonah and Zoar and compare their genetic types to those in established colonies at Laurel Lake in western Massachusetts. Laurel Lake has been studied as a possible source for the local populations due to Laurel’s flow into the Housatonic River headwaters, and field work conducted as part of the WCSU study confirmed the presence of zebra mussel larvae in two water routes from Laurel to the Housatonic. Yet subsequent DNA analysis reached the significant preliminary finding that the Lillinonah and Zoar colonies’ genetics show significant differences from those in Laurel, which has led Wong to investigate potentially closer linkages to more distant colonies in Lake Champlain and the Hudson River — linkages which, if confirmed, would strongly suggest that zebra mussels were introduced in western Connecticut reservoirs from boats and other craft contaminated elsewhere in the region.

Candlewood Lake Authority Executive Director Larry Marsicano, also a co-author of the report, said the lake’s multiple boating access points through two state launches, five town launches, and numerous private community and homeowner sites pose a major challenge in promoting voluntary checks of incoming craft for invasive species contamination. Marsicano noted pilot voluntary inspection programs planned for the Brookfield town launch site on Candlewood, as well as for one state launch, promise to provide a model for monitoring craft-borne infestations and making free decontamination facilities available to boat owners.

Wagener emphasized the importance of bringing all stakeholders in western Connecticut lakes together in collaboration to study invasive species problems in the region’s fresh-water resources and possible strategies to contain or arrest their expansion. The four-year study of zebra mussel populations in local reservoirs relied upon the research skills of WCSU biology faculty and students, the financial backing of the Connecticut Department of Energy and Environmental Protection, and significant support from the Candlewood Lake Authority (CLA), Lillinonah’s Friends of the Lake, and the Lake Zoar Authority. This broad base of collaboration, reinforced by contributions of individual volunteers from the area, represented a successful exercise in “community science,” Wagener said. “They know the lakes, we have the science, and it’s a wonderful way to involve our faculty, students and alumni to achieve this synergy with community participants.”

Marsicano’s field work at Candlewood began in the 1980s as a Western student research assistant to a faculty mentor, and he remains active at WCSU as an adjunct professor of biological and environmental sciences. He continues to lead monitoring at the lake using WCSU equipment to detect any signs of zebra mussel presence. He also has collaborated with Dr. Kevin Kelly, a Colorado-based scientist for the federal Bureau of Reclamation, to explore the potential use of carbon dioxide injections as a means to eradicate established zebra mussel colonies, and hopes to expand the pilot project with DEEP support to determine if carbon dioxide also can kill zebra mussels at the larval stage.

The CLA and WCSU biologists have conducted joint research investigations over the past decade to address the proliferation of Eurasian watermilfoil, an invasive plant species whose annual regeneration along the Candlewood shoreline poses a significant nuisance to boating and other recreational activities. A research paper co-authored by Wagener, Marsicano and Dr. Thomas Lonergan, formerly a member of the WCSU biology faculty, sought to determine the effectiveness of annual winter drawdowns of Candlewood Lake in preventing regrowth from the previous summer season by freezing or drying out milfoil roots in the shore areas exposed by the lowered water level. Their conclusion was that a hard freeze exposing roots to a temperature at -5 degrees Celsius for more than 24 hours, or a sustained drying of roots at 4 degrees Celsius for more than 48 hours, would be sufficient to prevent regrowth.

Yet variations in the duration, timing and prevailing weather conditions for these winter drawdowns by FirstLight Power Resources, which manages the Rocky River station on Candlewood Lake for hydroelectric energy generation, result in considerable differences in their effectiveness in controlling milfoil regeneration from year to year. “This study confirmed you can do a drawdown the right way, or you can do a drawdown with less effect,” Marsicano said. With water levels often not reaching their lowest level until mid-January, he noted, “we learned the exposed shoreline was not reaching freezing temperatures in some years, and that snow cover often insulated the ground and lessened the effectiveness of the drawdowns. Last winter we had a hard freeze in January and it did kill the milfoil more effectively.”

Another CLA collaboration with Western involves the recent introduction of Asian grass carp in Candlewood Lake to feed on milfoil as part of their vegetarian diet. Marsicano said the authority is working with Dr. Dora Pinou, WCSU professor of biological and environmental sciences, to track carp activities in areas selected for their extensive milfoil growth each year to determine their impact in managing the problem.

The CLA and Western biologists now have begun to investigate the increasingly prevalent concern of blue-green algae blooms, also known as cyanobacteria, on the surface of Candlewood Lake during the summer months, which forced the temporary closures of three town beaches on the lake this year. A particular focus for Wong has been the study of cyanobacterial genes to determine which types have the capacity to produce toxins that pose a public health risk in sufficiently high concentrations.

Marsicano and Wagener emphasized the need for further research to determine whether the surge in algae blooms during the past three years reflects the impact of climate change and increased phosphorus leaching into Candlewood Lake from septic systems, agricultural, horticultural and other human activities. “We may not be able to change the climate or the population density along the lake,” Marsicano said, “but we can have an impact on the algae nutrients that go into the lake.”

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