Development of disease resistance among Chesapeake Bay oysters calls for a shift in oyster-restoration strategies within the Bay and its tributaries. That's according to a new study by researchers at the Virginia Institute of Marine Science (VIMS).
The study, by professors Ryan Carnegie and Eugene Burreson, is the feature article in the most recent issue of Marine Ecology Progress Series. It is based on 50 years of VIMS research into the prevalence of MSX disease among the native eastern oyster Crassostrea virginica.
Carnegie, a Research Assistant Professor in the Shellfish Pathology Laboratory at VIMS, says "Our results point to substantial reproduction by disease-resistant oysters in the high-salinity areas where the parasite causing MSX thrives. We thus argue that reefs in areas of higher salinity should be the focus of conservation and restoration efforts, not just those in disease-free lower salinity areas."
MSX is caused by the single-celled parasite Haplosporidium nelsoni. It first appeared in Chesapeake Bay in 1959, combining with overharvesting, declines in water quality, and a second parasitic oyster disease known as Dermo to push the Bay's oyster population to one percent of historical levels. Both MSX and Dermo favor the saltier waters of the Bay's main stem, decreasing in prevalence as one moves upriver into the fresher waters of Bay tributaries, which form a safe haven from the parasites and diseases.
To date, restoration strategies have rested on the idea of protecting these "low-salinity refugia" as sources of larvae for replenishment of disease-ravaged populations in saltier areas of the Bay. These strategies are based on the high levels of mortality traditionally seen among oyster populations in saltier waters (initially more than 90 per cent), and computer models showing that tidal currents can indeed carry oyster larvae downriver from fresher to
|Contact: David Malmquist|
Virginia Institute of Marine Science