For Immediate Release - May 30, 2013

State Environmental Officials Warn Residents About the Discovery of Didymo

BOSTON – Thursday, May 30, 2013 – Officials from the Massachusetts Departments of Fish and Game (DFG) and Conservation and Recreation (DCR) are informing residents that the presence of the Didymosphenia geminata (didymo) was recently detected in the Green River in the Berkshire County towns of Alford and Egremont. This finding is the first confirmed occurrence of didymo in Massachusetts. 

“The Department of Fish and Game and its Division of Fisheries and Wildlife are trying to inform the public as quickly as possible about the recent discovery of didymo in Massachusetts, and provide best available information about how to help prevent the spread of this freshwater algae,” said DFG Commissioner Mary Griffin.

Didymo is a freshwater algae that occurs in North America and generally favors cold, clear, nutrient-poor waters with a neutral or slightly basic pH. Blooms can produce dense covering on rocky substrate and eventually result in long, unsightly stalks. Didymo may appear gray, brown or white and have texture comparably to wet wool or cotton balls. Extensive didymo blooms can cover river substrate, and may temporarily impact aquatic habitat, specifically cover stream bottoms, and make swimming, boating and fishing difficult and/or less desirable. 

Samples were collected and a preliminary identification was made by DFG’s Division of Fisheries and Wildlife (MassWildlife) Western District biologists. On Thursday May 23, 2013, the sample identification was confirmed by Vermont environmental officials, who have extensive experience with didymo. 

MassWildlife staff will post signs alerting the public to the presence of didymo in the Green River and how to clean recreational equipment and gear after each use. Although there is no known method for eliminating didymo from a waterway or controlling a bloom, all recreational boat users should always thoroughly wash their equipment, clothing, waders and boats in hot, soapy water. Boats, equipment and other non-absorbent materials should be scrubbed. Soft, absorbent materials should soak in hot, soapy water for a minimum of 30 minutes. This is particularly important with felt-sole waders or other slow drying material such as sneakers, towels, etc.      

In addition, DFG and DCR will work with the Massachusetts Department of Environmental Protection to provide information to the public about how to reduce the spread of didymo and other aquatic invasive species.

“Didymo is the latest in a series of nuisance aquatic species to impact the Commonwealth’s lakes, ponds and streams,” said DCR Commissioner Edward Lambert. “We encourage the public to clean all boats and equipment before moving from one water body to another.” 

DFG staff has developed best management practices and disinfection procedures for field activities and fish stocking to minimize the spread of both aquatic invasive species, like didymo and zebra mussels, and pathogens in Massachusetts’ waters. DFG staff will also continue to monitor national and international research pertaining to the biology and management of didymo.

Didymo is visually undetectable without a microscope, unless it has established “colonies” on rock surfaces or is in a “bloom” phase. In addition to several western states, didymo has been found in Connecticut, Maryland, New Hampshire, New York, Pennsylvania, Vermont and Virginia. In New England, there have been no reported changes to fishery communities resulting from the sporadic blooms.

It is unknown if didymo was always present in the waters where blooms have occurred or is a recent introduction. 

In North America, the earliest recorded occurrence of didymo is from Vancouver Island in the late 1800s. One hundred years later, didymo formed nuisance blooms on the island’s Heber River and now blooms have appeared in two-thirds of Vancouver Island’s rivers. Didymo blooms, and the frequency of blooms, may vary widely between watersheds because of differing environmental conditions.  

DFG is responsible for promoting the conservation and enjoyment of the Commonwealth's natural resources. DFG carries out this mission through land protection and wildlife habitat management, management of inland and marine fish and wildlife species and ecological restoration of fresh water, salt water and terrestrial habitats. DFG promotes enjoyment of the Massachusetts environment through outdoor skills workshops, fishing festivals and other educational programs, and by enhancing access to the Commonwealth's rivers, lakes and coastal waters.

The Massachusetts Department of Conservation and Recreation (DCR), an agency of the Executive Office of Energy and Environmental Affairs, oversees 450,000 acres of parks and forests, beaches, bike trails, watersheds, dams, and parkways. Led by Commissioner Edward M. Lambert, Jr., the agency’s mission is to protect, promote, and enhance our common wealth of natural, cultural, and recreational resources. To learn more about DCR, our facilities, and our programs, please visit Contact us at