A first-of-its-kind study led by William & Mary's Batten School & VIMS is predicting estuaries along the East Coast of the U.S. will experience marine heat wave conditions for up to a third of the year by the end of the century. With estuaries serving as important nursery habitats for nearly 75% of all fish species and supporting more than 54 million jobs, this could have devastating consequences for marine ecosystems as well as the fisheries and communities that depend on them.

The study, published in Scientific Reports, used long-term monitoring data from the National Oceanic and Atmospheric Administration's (NOAA) National Estuarine Research Reserve (NERR) program to examine conditions in 20 estuaries across the U.S. over the past two decades. The results showed rising frequencies of marine heat waves in East Coast estuaries that—if continued as modeled—could have disastrous ecosystem consequences.

"The Chesapeake Bay, for example, currently experiences marine heat wave conditions approximately 6% of the year (22 days per year), and that is already placing stress on the ecosystem. Our study shows that estuaries across the East Coast could experience these conditions for more than 100 days of the year by 2100," said Batten School & VIMS Assistant Professor Piero Mazzini, co-author and academic advisor to lead author Ricardo Nardi. "This research should serve as a warning to policymakers and environmental managers who are charged with protecting these important ecosystems."

The news was better for West Coast estuaries, which did not show significant warming trends and may serve as important future refuges for many species. The researchers hypothesized that this was due to persistent wind-driven regional upwelling in the Pacific Ocean, which brings deep, cold water up to the surface.

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