Jellyfish Alert! Check NOAA’s Free Chesapeake Bay Forecast Before You Swim

SOUTHERN MARYLAND — Whether you’re planning to cool off at a beach, anchor in a quiet cove or spend the day kayaking, there’s one forecast you may want to check before heading onto the Chesapeake Bay this summer — the jellyfish forecast.

The National Oceanic and Atmospheric Administration’s National Centers for Coastal Ocean Science offers a free experimental Sea Nettles Probability Forecast that helps predict where jellyfish are most likely to be encountered throughout the Chesapeake Bay and its tidal tributaries.

The forecast uses water temperature and salinity to estimate where bay nettles are most likely to occur. While NOAA’s forecasting tool refers to “sea nettles,” scientists with NOAA, the Smithsonian Institution and the University of Delaware confirmed in 2017 that the Chesapeake Bay jellyfish is actually a distinct species known as the bay nettle (Chrysaora chesapeakei).

For nearly 175 years, it had been grouped with its larger ocean-dwelling relative, the Atlantic sea nettle (Chrysaora quinquecirrha), before genetic testing revealed they were two separate species.

The bay nettle (Chrysaora chesapeakei) is the jellyfish most commonly found in the Chesapeake Bay during the summer. Most are white, although those found in the southern Chesapeake Bay often have reddish-maroon markings. The interactive forecast doesn’t predict how many jellyfish are in the water. Instead, it estimates where you’re most likely to encounter them, helping swimmers, boaters and paddlers avoid painful stings.

For Southern Maryland residents, the forecast covers much of the Chesapeake Bay and several local waterways, including portions of the Patuxent River and Potomac River.

More Than Just A Painful Sting

Although they’re often viewed as a summertime nuisance, bay nettles play an important role in the Chesapeake Bay ecosystem. They feed on comb jellies, one of the primary predators of young Eastern oyster larvae. By keeping comb jelly populations in check, bay nettles help improve the survival of oysters, one of the Bay’s most iconic and economically important species. Bay nettles also serve as a food source for some fish and sea turtle species while providing shelter for the young of several commercially important fish.

Scientists say identifying the Chesapeake Bay jellyfish as a distinct species has improved research into where bay nettles live, how they respond to changing environmental conditions and how forecasting models can better predict where they’re likely to occur.

Residents planning a day on the water can check NOAA’s daily Sea Nettles Probability Forecast before leaving home.

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