FOR RELEASE ON FRIDAY, JAN. 22, 1999
For Further Information
Contact: Eileen E. Hofmann January 21-23 AAAS Meeting, Marriott Hotel 714-750-8000 Old Dominion University After January 24 at 757-683-5334
[email protected]
SPREAD OF OYSTER DISEASE LINKED TO CLIMATE CHANGES
ANAHEIM,CA. The spread of oyster disease in Chesapeake and Delaware Bays, and northward along the Atlantic Coast, may be triggered by climate change reports Old Dominion University researcher Eileen E. Hofmann in a presentation today (Jan. 22) at the annual meeting of the American Association for the Advancement of Science.
In worked funded under the National Sea Grant College Program's Oyster Disease Research Program, Hofmann and her research colleagues æ John M. Klinck, Old Dominion University; Susan E. Ford and Eric N. Powell, Haskin Shellfish Research Laboratory, Rutgers University æ report that that the northern spread of the parasitic oyster diseases MSX and Dermo can be linked directly to changes in winter water temperature which reflect climate warming.
Hofmann reports that "Environmental conditions of temperature, salinity and oyster food supply provide the external forcing that results in variations in these biological rates. Simulations that use time series characteristic of warm and cool periods show the advantage given both parasites by warm conditions, and demonstrate the importance of a sequence of warm and dry years in triggering wide spread epizootic conditions of the two diseases."
Susan Ford and the research team looked at the historical record of monitoring for oyster diseases and founded direct evidence that increased winter water temperatures have been important in the recent outbreak of MSX along the Mid-Atlantic and Northeastern Atlantic coastline. Both diseases are warm-water parasites that infect a variety of oysters around the world.
Hofmann and colleagues developed two models that simulate the host-parasite-environmental interactions of Eastern oysters (Crassostrea virginica) and the pathogens, Haplosporidium nelsoni, which causes the disease MSX, and Perkinsus marinus, which causes the disease Dermo.
The models are physiologically-based and structured around the proliferation and death rates of both parasites under different environmental conditions. Equations describing these rates were constructed using data from long-term field observations, and field and laboratory experiments. Simulations were developed that use environmental conditions characteristic of
Delaware and Chesapeake Bays to reproduce the observed seasonal disease cycles and consequent oyster mortality. These simulations showed the effect of environmental factors, such as salinity and cold temperatures on controlling the intensity and prevalence of infections.
Hofmann says that "results of these simulations can be used to understand the causes underlying the northward spread of these two oyster diseases along the east coast of the United States, from Chesapeake Bay to Maine, in the decade of the 1990s."
An additional significance of Hofmann's report is the implications for resource management of the shellfish which is valuable commercially and important environmentally because of its tremendous filtering ability which can help stabilize coastal estuaries' environmental systems.
"Our findings," says Hofmann, "demonstrate how important climate is in regulating diseases such as Dermo and MSX. We have to manage the disease populations with a long-term climate perspective which means that you have to be aware of such occurrences as an El Nino or other climatic effects. You cannot set management strategies based simply on what you see this week or what you've done in the past."
Hofmann's research was previous reported at the International Conference on Shellfish Restoration, hosted by South Carolina Sea Grant at Hilton Head, SC in November 1998. Previous reports of it also have been published over the past two years in peer-reviewed articles in the Journal of Shellfish Research.
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