Chesapeake Bay Vibrio Bacteria Study

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Researchers have found that three common species of Vibrio bacteria in Chesapeake Bay could increase with changing climate conditions by the end of this century, resulting in significant economic and healthcare costs from illnesses caused by exposure to contaminated water and consumption of contaminated shellfish.

The study, the first to apply a new way of downscaling global climate models to the Chesapeake Bay, was conducted by National Oceanic and Atmospheric Administration (NOAA) scientists and colleagues. It appears in the American Geophysical Union journal GeoHealth.

Vibrio bacteria occur naturally in the Chesapeake Bay and in coastal and estuarine waters around the world. About a dozen Vibrio species can cause human illness, known as vibriosis.

Two of the most common species causing human illness in the United States, Vibrio parahaemolyticus and Vibrio vulnificus, occur in the Chesapeake Bay. Their abundance varies with water temperature, salinity, and other environmental factors.

A third species, Vibrio cholerae, also occurs in Chesapeake Bay but is not associated with cholera epidemics, although like other Vibrio species it can sometimes cause illness in people who eat contaminated shellfish, such as oysters.

Researchers used four different global climate models and data from eight locations in and around the bay and its tributaries to project how warming temperatures and changing freshwater inputs might impact the three Vibrio bacteria in the bay and its oyster populations by the end of this century.

The findings showed substantial future increases in the occurrence, distribution, and length of the season for V. vulnificus and V. parahaemolyticus, and an increase in favorable habitat for V. cholerae, although this was confined to low salinity regions of the bay.

IPCC, the Intergovernmental Panel on Climate Change, is the international body that reviews and assesses the most recent scientific, technical, and socio-economic information produced worldwide relevant to the understanding of climate change. CIMEC is a partnership of ocean, climate, and ecosystem research between NOAA and several California universities.

Laboratory experiments suggest that optimum temperatures for Vibrio species are between 37 and 39 degrees C, or 98.6 to 102.2 degrees F, much warmer than current conditions in the Chesapeake Bay.

All three Vibrio strains now occur more frequently and in higher abundances in warmer months of the year, when water temperatures are also warmer. Each strain or species appears to have a distinct salinity range, meaning the Vibrios could potentially increase only when other environmental factors are or become favorable in a specific area in the bay.

Disease risk from Vibrios already exists in the Chesapeake Bay. Environmental and resource managers are aware of it, as are many local residents and shellfish consumers.

Some measures designed to reduce the risk of Vibrio-related illness from harvested oysters are already in place. For example, in warmer months, oysters must be refrigerated by a certain time of day after being harvested.

As temperatures continue to warm, these set times of day may need to be adjusted to ensure that oysters remain safe to eat. The months of the year where these regulations are applied may also need to be extended.

Since many commercial and recreational fisheries species use estuaries during their life cycle, the downscaled climate framework used on Vibrio could be applied to them as well.

In addition to Barbara Muhling and Vincent Saba, other authors on this study are John Jacobs of the National Centers for Coastal Ocean Science of NOAA’s National Ocean Service in Oxford, MD; Charles Stock of the NOAA Geophysical Fluid Dynamics Laboratory in Princeton, NJ; and Carlos Gaitan of Arable Labs Inc. in Princeton, NJ.

source: NOAA Northeast Fisheries Science Center

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