The Colonization of Chesapeake Bay
"The Chesapeake Bay is the largest single recipient of Ballast water on the East Coast." -Executive Director of the Chesapeake Bay Commission. "A recent shipping study conducted for the U.S. Department of Transportation (Carlton et al.1995) found that the two ports of Norfolk and Baltimore receive 9,325,000 and 2,834,000 metric tons of ballast water per year, respectively. Furthermore this water originates from 48 different foreign ports."
Exotic Species that arrive in U.S. waters can alter ecosystems and potentially change food webs, spread diseases, introduce biological toxins, and replace commercially importantspecies with unharvestable varieties. -Maryland Sea Grant, 1996-97
Every hour an average of more than two million gallons of foreign plankton, are released in U.S. waters.
"These species contributed significantly to the listing of 160 native species as endangered or threatened under the Endangered Species Act." - U.S. Fish and Wildlife Service, 1993-report
Examples:
Zebra Mussel: has clogged municipal and industrial water intake pipes and outcompeted native mussel populations in several major water bodies across North America. Also responsible for shellfish poisoning, and declining commercial and sport fisheries.
A Strain of Cholera: responsible for paralytic shellfish poisoning, declining commercial and sport fisheries, and human disease. In humans, Bacterium Vibrio Cholera: causes a viral illness of the small intestines, which results in diarrhea and possibly death.
Japanese shore crab Hemi-grapus sanguineus: is now well-established and rapidly expanding along the Atlantic coast from Chesapeake Bay to Cape Cod.
Other Invasive species include: barnacles, crustaceans,
clams, fish, copepods, diatoms, dinoflagellates, flatworms, crabs, shrimp
, freshwater Asian clam, and xanthid crabs.
Strategies to Decrease the Risks of Future Introductions through Ballast Water Management:
Attempts to manage the threat of ballast water-related invasions have come from many levels of government in many different nations. Although a number of countries have implemented voluntary initiatives, no international policy mandate has emerged.
"The General Assemblies of Virginia, Maryland, and Pennsylvania are now considering resolutions memorializing the U.S. Congress and the U.S. Coast Guard to implement programs and fund research that will prevent the introduction of nonindigenous species via ballast water." -Ann Swanson, Exec.Dir. Chesapeake Bay Commission
The Chesapeake Bay Commission is a tri-state legislative Commission serving the General Assemblies of Virginia, Maryland, and Pennsylvania that helps to guide the states in cooperatively managing the Chesapeake Bay.
Click here for the policy developed by: the Leaders of the Chesapeake Bay Program. The policy addresses both intentional and unintentional introductions of acquatic nonindigenous species, and lays out a framework of cooperative management approaches and public outreach efforts for both.
Ecological, Economic, and Social Impacts:
The impacts of nonindigenous species are many, and include ecological, economic, cultural, and social considerations. Past introductions of nonindigenous species have resulted in numerous declines in populations of native species (in many cases to the point of extinction) and alterations of entire ecosystems. (OTA, 1993)
In addition to ecological effects, nonindigeous species can have adverse economic and social impacts as well. For zebra mussels alone, the U.S. Congress (OTA Report 1993) has estimated that, nationwide costs will exceed $3 billion dollars over the next decade to prevent the clogging of municipal and industrial water supplies by dense zebra mussel aggregations. This large figure is in dollar terms as of 1991and only pertains to water systems; other segments of the economy, such as commercial shipping nad recreational boating, are not represented in the estimated costs. Furthermore, the direct economic impact of this invasion will continue to grow because the future distribution of these mussels may include much of North America. (Strayer 1991)
Indirect economic impacts have occured due to the introduction of invasive species in Chesapeake Bay. Reservoirs surrounding Baltimore City, Maryland, (Liberty, Loch Raven, and Pretty Boy reservoirs) were closed to boat angling during 1992 in response to the threat posed to municipal water supplies by the zebra mussel. The closure was instituted to reduce the risk of introduction of zebra mussels while the city of Baltimore selected and installed zebra mussel control devices. These reservoirs provide excellent angling opportunities for city residents, and over time a number of businesses have emerged to support this local sport fishery. When the reservoirs were closed to boat fishing, 10 fishing-related businesses reported losses of up 75 percent of gross sales. (D. Terlizzi, pers.com). The combined losses are estimated in the hundred of thousands of dollars. It is important to note that this economic loss preceded the arrival of the invading species. Thus, the threat alone of an invasion can lead to economic losses not associated with direct damage to an ecosystem or human infrastructure.
Impacts on human health. Certain toxic marine planktonic algae, for example dinoflagellates, can produce anoxic events and fish kills, and also may lead to human poisoning and fatalities. Transported in ballast water as microscopic cysts, these small organisms often release toxins that enter the food chain, and may accumulate in the tissue of shellfish. Human consumption may then result in paralytic shellfish poisoning, diarrhoeic shellfish poisoning, neurotoxic shellfish poisoning, amnesic shellfish poisoning, and ciguatera conditions that may laed to hundred of deaths and countless illness worldwide.
Contact Ann Swanson, Executive Director of the Chesapeake Bay Commission @ (410) 263-3420 or fax (410) 263-9338.
