Model predicts chance of encountering jellyfish. (A Stinging Forecast).

Weather forecasters usually prognosticate precipitation, pollen, and poor air quality. Soon, in some areas, they could provide beachgoers with the probability of confronting a jellyfish.

True to its common name, the East Coast sea nettle, Chrysaora quinquecirrha, lives along the United States' eastern shore and plagues swimmers with painful welts. Although the creature's found from Cape Cod to the Caribbean, it particularly afflicts the brackish waters of the Chesapeake Bay, says Mary Beth Decker, a marine ecologist at Yale University. The polyp form of the jellyfish lives in the bay's shallows during the winter. But from May through August, buds the size of a BB break off the polyps and rapidly grow into sea nettles that can reach the size of a dinner plate. Besides mining a day at the beach, sea nettles prey on fish eggs, fingerlings, and small crustaceans.

Free-swimming sea nettles typically occur only in waters with certain combinations of temperature and salinity, says Christopher W. Brown of the National Oceanic and Atmospheric Administration (NOAA) in Camp Springs, Md. Now, he, Decker, and their colleagues have used data related to sea nettle sightings since 1987 to develop a mathematical model that estimates the probability of finding the noxious jellyfish at various spots throughout the Chesapeake Bay. The researchers describe their technique in the July 23 Eos.

The current version of the scientists' computer simulation gets its salinity and temperature input from a U.S. Army Corps of Engineers model that considers winds, tides, and the volume of flow in the rivers that carry fresh water into the bay.

Although the NOAA technique is fairly successful at predicting sea nettle presence along the length of the Chesapeake, it hasn't done as well in estimating their presence across the width of the bay, says Brown. Incorporating other factors that influence sea nettle populations, such as the availability of prey, could refine the model. Once it's fine-tuned, the researchers plan to use temperature and salinity data from buoys and satellites in their calculations.

George I. Matsumoto, a marine biologist at the Monterey Bay Aquarium Research Institute in Moss Landing, Calif., says the team's model will be a "useful tool in an area of ongoing research of broad economic and ecological importance."

Once Brown and his team can successfully predict sea nettle populations at any given point in the Chesapeake, they'll attempt to expand the technique to outbreaks of other undesirable organisms, such as toxic algae and the fish-killing microbe Pfiesteria piscicida (SN: 9/6/97, p. 149).