An ongoing threat: Zebra Mussels in Massachusetts
Posted by Tyler
Zebra Mussels (Dreissena polymorpha) are an invasive mollusc species, native to the Black Sea, that has – since its introduction to North America in 1988 – spread into many of Americas waterways with alarming speed.
Over the course of their 5 year lifespan, Zebra Mussels grow to be 1-2 inches long and are yellow with dark “zebra-like” bands running along their shells. They spend the beginning of their lives as free swimming larvae before settling onto an appropriate surface and entering the adult phase of their life-cycle. As adults they’re immobile and rely on their thick shells for protection from predation.
The environmental threat posed by Zebra Mussels can be traced to their amazing success at colonization; in some cases upwards of 700,000 adult mussels have been found on 1 square meter of suitable substrate. Zebra mussels are able to settle and grow on almost any solid surface, much to the detriment of most species around them. Beyond the simple fact that their presence can crowd out other species of shellfish they are highly efficient filter feeders. Filter feeders derive nutrition by pulling small particles of organic matter out of the water. In areas that have been taken over by Zebra Mussels this action can make the water significantly clearer. This change in water clarity can allow other species of aquatic plants, previously absent in invaded lakes and streams, to grow and flourish, and the lack of organic material in the water can cause other species of fish to go hungry.
Beyond the environmental threat is the danger that the mussels pose to boats, underwater pipes, and intake valves. Cleaning surfaces upon which they have established themselves is an intense process which costs millions of dollars a year. Additionally, the shells left over when Zebra Mussels die are sharp and can wash ashore in such great numbers that they completely cover beaches surrounding areas where they are prevalent.
Zebra Mussels were first discovered in Massachusetts in July of 2009 in Lake Laurel. Several Massachusetts governing bodies, including the Massachusetts Department of Fish and Game, quickly drafted a plan to respond to the threat posed by a successful invasion by the molluscs. The object of their initial efforts was largely to contain the invasion while a more comprehensive plan could be drawn up by closing the boating ramps and requiring that all boats be stored out of water for the duration of the season. Unfortunately, these temporary measures did not succeed in containing the spread of the mussels.
Currently there are several ways of dealing with Zebra Mussels. Obviously, manual removal, while effective at removing the mussels from where they have become established, is labor intensive and expensive. Studies have shown that they are vulnerable to high temperatures, and die when the water around them reaches 110 degrees Fahrenheit. Finally, because of the nature of their reproduction some scientists believe that it might be possible to interfere with their ability to breed. If that were to be the case then the state officials currently fighting the spread of Zebra Mussels would have a powerful new weapon to help with their work.