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| Dangerous Invaders Zebra mussels, with their characteristic striped shells, have arrived in Massachusetts waters, spawning aggressive efforts to contain their spread. Zebra mussels are small—averaging only about one inch in length—but their impact in ecosystems is large, and their ability to clog water pipes is extremely damaging. Photo courtesy of Massachusetts Department of Conservation and Recreation |
The Green Corner
By Sarah Peters, NEIWPCC
Most New Englanders would agree that the summer of 2009 was not ideal for anyone who owns a boat or enjoys time by the water. Gray skies, frequent rains, and cool temperatures made June feel like April. So, when warm sunny days finally did arrive, many people dashed to lakes, ponds, and rivers. Unfortunately, those who spend time on one western Massachusetts lake soon encountered an environmental nightmare.
In late June, a beach worker at Laurel Lake, located in the Berkshire County towns of Lee and Lenox, discovered a zebra mussel on a beer can that had washed ashore. After the state Department of Conservation and Recreation (DCR) confirmed the presence of the invasive species, state officials temporarily closed the boat ramp on the lake as they investigated the extent of the mussel establishment. Discovering a new occurrence of any aquatic invasive species in a water body is unfortunate, but finding zebra mussels is particularly worrisome and problematic. What are these pesky creatures, and why do we fear them so much?
Unwelcome Guest
Zebra mussels, scientifically known as Dreissena polymorpha, are native to Eastern Europe, and it is believed they came to the United States via the ballast water of trans-Atlantic freighters. The first discovery of the mussel in this country was in 1988 in Lake St. Clair, located between Lake Erie and Lake Huron. But they soon made their way into many other places, including the Mississippi River and its major tributaries, all the Great Lakes, the Chesapeake Bay watershed, and the Northeast states of Connecticut, New York, and Vermont.
This rapid spread was no minor matter. Zebra mussels are considered one of the worst invasive species found in the United States, and they recently made it onto Time magazine’s list of the top ten invasive species in the world. They are the only freshwater mollusk that can attach to solid objects, such as rocks, logs, docks, and boats. Zebra mussels grow in large clusters that can clog water-intake pipes, posing problems for power plants, steel plants, and drinking water supplies. Research has estimated that from 1993 to 1999, zebra mussels cost the power industry alone $3.1 billion, while other industries, businesses, and communities incurred costs of approximately $5 billion. But money is not the only concern. The shells are so sharp they can cut swimmers’ feet. Mussels also alter ecosystems by affecting nutrient cycling and food web dynamics, creating undesirable habitat for other aquatic species, and influencing the fate and transport of contaminants.
With zebra mussels already found in the Northeast, are all lakes at risk or are some safe? While it is not possible to guarantee any water body is safe from zebra mussel contamination, there are some water bodies where the mussels are more likely to take up residence. Studies show that substrate type, pH, calcium concentrations, and alkalinity are the most important factors in zebra mussels’ ability to reproduce and colonize. Zebra mussels prefer waters with a pH of 7.4 or greater and calcium IWR, Winter 2010 Page concentrations of 20 milligrams per liter or higher. In 1993, researchers at the University of Massachusetts Amherst looked at pH levels and calcium concentrations in Massachusetts watersheds to estimate potential zebra mussel habitat; based on groundwater and river survey data, they determined that the Hoosic and Housatonic watersheds are the only areas highly susceptible to colonization. Laurel Lake is in the Housatonic watershed.
Prepared for Action
While the arrival of zebra mussels in Massachusetts was certainly not welcome, state agencies knew it was a real possibility given the species’ presence in three bordering states, and preparations had been made. In 2005, DCR published a Rapid Response Plan for the zebra mussel that was based on a template recommended by the Northeast Aquatic Nuisance Species Panel, in which NEIWPCC has been active for many years. The plan outlined steps DCR would take if the species was discovered in Massachusetts, and DCR diligently followed the monitoring and surveillance program. All the work was driven by a simple principle: since eradicating an established colony of zebra mussels is a daunting challenge, the key to dealing with them effectively is early detection and rapid containment.
DCR began two programs still in existence today. Through the Boat Ramp Monitoring Program, volunteer boat ramp monitors work from Memorial Day to Labor Day, inspecting boats and talking to boaters about ways to prevent or minimize the spread of aquatic nuisance species from one water body to another. In 2008, DCR initiated a Zebra and Quagga Mussel Monitoring Program for lakes in western Massachusetts determined to be at the greatest risk of zebra mussel establishment due to water chemistry and proximity of existing infestations in neighboring states. Through this program, volunteers are provided with equipment and trained to collect samples and identify zebra mussels. The program covers ten lakes, including Laurel Lake. In fact, it was a DCR-trained volunteer who discovered the first zebra mussel at Laurel Lake.
Once zebra mussels were found, the state acted fast. Following the protocols in the Rapid Response Plan, DCR recommended to the Department of Fish and Game’s Office of Fishing and Boating Access (OFBA) that the Laurel Lake boating access be temporarily closed. On July 8, the director of OFBA closed the boat ramp on an emergency basis, giving the state time to investigate the scope of the problem, consider the risk of transport to other water bodies, and determine appropriate management strategies. Two days later, OFBA established a new emergency management measure regarding the use of state boat ramps at other Berkshire County water bodies determined by DCR to have calcium concentrations and other chemical and physical characteristics to support breeding populations of zebra mussels. The measure authorized managers of boat ramps to prevent their use by boats determined to have been on Laurel Lake in the previous 30 days, unless the boat was cleaned and disinfected as specified by the state. On July 23, OFBA expanded the use restrictions by authorizing municipal or local managers of boat ramps to prevent access to boats that had been on Laurel Lake or any other water body with zebra or quagga mussels within the previous 30 days, unless the boat had been properly decontaminated. Ramp access could also be denied if the manager observed visible evidence of an aquatic invasive species on a boat.
On July 15, the state took one more step, as DCR temporarily prohibited fishermen from using private boats at the Quabbin Reservoir’s three fishing areas. While it is unlikely the Quabbin’s water chemistry would support establishment of zebra mussels, the reservoir’s importance as a drinking water source for many communities and the risk mussels pose to water intake structures were enough to convince DCR and the Massachusetts Water Resources Authority of the need to restrict access until further studies could be conducted and boat cleaning procedures established. DCR divers later surveyed the entire reservoir and found no mussels, and the department undertook a full analysis of the conditions and chemistry of the reservoir. DCR is now evaluating procedures and potential long-term options to allow for recreational boating on the Quabbin while strongly protecting against invasive species entering the water supply.
To further understand the risk of zebra mussels in western Massachusetts, DCR hired the consulting firm Biodrawversity in the fall of 2009 to assess 17 Berkshire County lakes and the main stem of the Housatonic River for the presence of zebra mussels and the potential to support the species based on physical, chemical, and biological parameters. Field work took place in September and October of 2009 and the report, which also includes data from three lakes surveyed by DCR, was published in November. Researchers found seven lakes to be at low risk for zebra mussel invasions, four lakes to be at medium risk, and nine lakes and the Housatonic River to be at high risk. Adult zebra mussels were found in Laurel Lake, Laurel Brook, and the Housatonic River. Zebra mussel larvae, known as veligers, were discovered only in Laurel Lake.
State of Containment
While it cannot be said that it is impossible to get zebra mussels out of a water body once they have a foothold, it has never been done before. So as in all states struck by an invasion, the focus in Massachusetts continues to be on preventing further spread. All state boat access areas that are considered at high risk for zebra mussel colonization due to water chemistry and proximity to Laurel Lake have been checked by DCR staff. Signs have been posted at the areas with specific information about zebra mussels for boaters, including guidance on cleaning boats and gear. And at Laurel Lake, a new sign clearly warns visitors of the zebra mussel infestation.
Moving forward, DCR and the Department of Fish and Game (DFG) are requiring all users of state boat ramps in the Hoosic and Housatonic watersheds to follow a set of actions to prevent the spread of zebra mussels, and the agencies are strongly recommending that these same actions be taken at public and private boat ramps and water bodies not under state control. DCR and DFG have also developed new boat ramp signage and educational brochures, as well as mandatory decontamination procedures, which include inspecting a boat after leaving a water body, draining all water from a boat, and thoroughly cleaning fishing and recreational equipment.
While DCR officials may be unhappy that zebra mussels have been found in the state, they deserve great credit for how well they have handled the situation. By acting proactively, they were prepared for the problem.
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| Sign of a Threat Visitors to Laurel Lake in Massachusetts are now greeted by a warning about the presence of zebra mussels and the need to take precautions to keep them from furthering their advance. Photo courtesy of Massachusetts Department of Conservation and Recreation |
“The volunteer monitoring program that was started as a result of the Rapid Response Plan in itself was a success by bringing this subject to the forefront with local lake residents,” said Tom Flannery of DCR’s Lakes and Ponds Program. “We didn’t have to start from scratch with educating people about the issue.”
The ultimate fate of zebra mussels in Massachusetts remains to be seen. At Laurel Lake, it appears the species is firmly established and water chemistry conditions make for an ideal environment. Whether the population continues to expand in the lake depends on adequate food and space. As for expansion elsewhere, studies suggest that populations in the Housatonic River may never reach the densities seen in lakes. In western Massachusetts water bodies as yet untouched by zebra mussels, prevention is the number one priority. DCR will need to continue outreach efforts and boat ramp monitoring programs, but responsibility also lies in the hands of anyone who uses the lakes.
To learn more about zebra mussels in Massachusetts, including decontamination procedures, visit DCR’s Lakes and Ponds Program at www.mass.gov/dcr/watersupply/lakepond/lakepond.htm
Susy King (sking@neiwpcc.org) is a NEIWPCC environmental analyst. She is currently serving as co-chair of the Northeast Aquatic Nuisance Species Panel’s Policy and Legislation Committee