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 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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