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Western studies focus on arresting spread of invasive species in area lakes

The fresh-water expanses of Candlewood Lake and other lakes across western Connecticut have become an important extension of the teaching and research experience at Western for Dr. Mitch Wagener, Dr. Edwin Wong and a dedicated corps of student assistants in recent years — and they are determined to carry on with scientific work that holds far-reaching relevance to environmental and public policy across the region.

For Wagener, professor and chairperson of the biological and environmental sciences department, the search for an effective means to contain the annual proliferation of the invasive weed Eurasian milfoil in shallows along Candlewood Lake’s 60-mile shoreline has provided the impetus for a research study now in its fourth year to determine if weevils that feed on the weed can become a viable biological tool to reverse milfoil spread.

In 2011 Wong, associate professor of biological and environmental sciences, joined Wagener in a new research undertaking to determine if the larvae, or veligers, of the diminutive but highly invasive shellfish species known as zebra mussels have spread throughout the Housatonic River watershed in Connecticut, including Candlewood Lake and Lakes Lillinonah and Zoar. Their team study, launched in a pilot project funded last year by the Connecticut Department of Energy and Environmental Protection (DEEP), has combined the standard laboratory analysis technique of microscopy with the powerful tools of DNA analysis to pursue a two-pronged approach in seeking to identify the presence of zebra mussel veligers in samples drawn from the three lakes as well as a fourth site on the Housatonic River.

Several students and recent graduates in the WCSU biology program played a critical role in the milfoil and zebra mussel projects, collecting field samples and conducting analysis in the lab. Wagener and Wong credited the sustained commitment during 2011 of research assistants Catrina Morgan, Melissa Garafola, Ana Bortoletto, Maria Bortoletto, Bruna Oliveira and Heather Shepard.

Building on the experience of monitoring milfoil weevil populations implanted at several shoreline locations by the Ohio-based firm EnviroScience, WCSU and its partner in the milfoil weevil project, Candlewood Lake Authority (CLA), plan to tighten the focus of study this summer to a single, relatively protected cove, Wagener said.

“We have found that if you just introduce weevils widely in the lake, the insects disperse and it is difficult to tell if you have done any good,” he observed. “We will use the cove as an enclosed nursery: If we can determine that the weevils are reducing the milfoil measurably in that cove, we will know that we are onto something.”

The quest for long-term strategies to contain or eradicate Eurasian milfoil growth in Candlewood Lake responds to heightened public awareness that proliferation of the pest weed causes significant disruption to boating, water sports and other recreational activities, as well as affecting the lake’s ecological balance in potentially harmful ways. This summer may prove especially challenging:The uncommonly mild winter, and the lack of an extended hard freeze in exposed shoreline areas during the seasonal drawdown of the Candlewood Lake reservoir, have increased the probability of a heavier-than-average proliferation of milfoil from late spring through early fall, Wagener noted.

Zebra mussels pose another serious risk to the environment, hydroelectric power generation, and recreational use of the Connecticut lakes in the Housatonic watershed, though their presence has not been confirmed to date in Candlewood Lake. “Zebra mussels are invasive, reproduce quickly, and attach themselves to many types of hard surfaces,” damaging everything from water intake pipes for power facilities to boat hulls and docks, Wagener said. The voracious consumption by zebra mussels or organic material in the water also leads to severe depletion of biodiversity in affected waters.

A study in fall 2010 that disclosed the first positive identification of zebra mussel colonies in Lakes Lillinonah and Zoar, along with previous confirmed reports of the invasive species’ presence in a western Massachusetts lake and brook connected to the headwaters of the Housatonic, inspired Wagener and Wong to collaborate with CLA Executive Director Larry Marsicano to launch a pilot program during 2011 designed to develop sampling and analytical techniques for early detection and ongoing monitoring of potential zebra mussel invasions. Supported by a $6,000 grant and logistical cooperation with the CLA, Lake Zoar Authority and Friends of Lake Lillinonah, Wagener and student research assistants made periodic visits to carefully selected locations on the three lakes to collect water samples and return them to Science Building laboratories for investigation using two analytical approaches:

·         Researchers view plankton samples through a light microscope and polarizing filters, searching for evidence of zebra mussel veligers in roughly oval form that glow in polarized light against a black background, with a dark cross-like shape in its middle. A potential specimen is viewed again without polarization for more careful examination of its form and features to distinguish positive veliger identifications from ostracod, shell and other similar-looking specimens.

·         Samples are subjected to a technique known as polymerase chain reaction (PCR) to assist in the identification of zebra mussel DNA in water samples. “The PCR machine can pick up DNA from a single hair follicle, or even a single cell, and copy it many times over until you have a large enough quantity for analysis,” Wong noted.

Wagener observed that groundwork laid in the pilot project to build a database of photographic images of veliger and other samples viewed under the microscope provide the foundation for more efficient and accurate identification of the presence of zebra mussel larvae going forward. Similarly, preliminary work in the pilot project has determined the set of PCR testing primers and conditions most conducive to separating the signature bands of zebra mussel DNA from the “background noise” of other organic materials in the plankton samples, which should yield greater clarity in DNA analysis.

“This is like an episode of CSI: We’re the DNA experts, the lakes are the ‘crime scene,’ and the suspect is the zebra mussel,” Wong said. “DNA analysis offers a powerful tool to distinguish species that on the surface look very similar,” complementing microscropy work that can often prove time-consuming and visually exhausting. “The goal is to find that one signature band from the zebra mussel among the huge pot of DNA from hundreds or thousands of species present in the samples we draw from the lake.”

 “It’s like listening for a whisper at a rock concert,” Wagener added.

DNA analysis holds particular promise in answering the unsettled question of whether zebra mussel populations found in Lakes Zoar and Lillinonah were transported as veligers downstream from lakes in western Massachusetts, or instead arrived on the hulls and in the water discharges of boats brought to the Connecticut lakes from the Hudson River and other known waterways affected by zebra mussel invasions. Wong noted that DNA from the Zoar and Lillinonah samples should show a match with DNA of the Massachusetts lake veligers if they traveled downstream from that source.

State DEEP funding will be requested to support continuation of the zebra mussel project during 2012. Over the longer term, additional resources are being sought to replace and upgrade laboratory equipment, expand student internship stipends, maintain supplies for continuing field studies, and build infrastructure to sustain and build the milfoil and zebra mussel research programs. Researchers have established several research objectives that will require additional funding, including:

·         Expanded monitoring to identify zebra mussel presence at Candlewood, Lillinonah and Zoar, through sampling at more sites and through equipment renovations to increase WCSU lab capacity to process samples on a larger scale and with greater efficiency.

·         Introduction of new areas of research related to the zebra mussel project including study of surface types that attract or repel veligers, and investigation of a proposal to use compressed carbon dioxide to eliminate veligers from streams and pipes.

·         Continuation of the milfoil weevil project over a multi-year period, as well as resumption of a second WCSU research project currently in hiatus to determine the effectiveness of Candlewood Lake winter drawdowns in eliminating milfoil through exposure of roots to freezing temperatures.

·         Multi-year surveys of invertebrate and plankton communities in the three lakes to gain better understanding how biodiversity is affected and changed by the presence of zebra mussels.

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