A team of researchers are working on a project funded by the U.S. Geological Survey’s (USGS) South Central Climate Adaptation Science Center to assess how changing conditions in the Gulf of Mexico might impact the valuable oyster fishery there. The study is led by USGS researchers at the Louisiana Cooperative Fish and Wildlife Research Unit and the USGS Wetland and Aquatic Research Center, where the research team is modeling how changing climate conditions may affect oysters in Louisiana and Texas and mapping locations most likely to support healthy populations moving forward. They are finding that the increased potential for extreme rainfall and storm events, rather than everyday warming, poses the biggest risks to Gulf of Mexico oysters.

New Orleans is the place to be for oyster aficionados. Raw or charbroiled, smoked, or fried, tucked into po'boys or bathed in soup, the Big Easy is the birthplace of some of the world’s most famous oyster dishes, all fresh from the Louisiana coast. But as temperature and rainfall patterns shift, shellfish harvesters and conservationists alike are concerned for future oyster harvest in the Gulf of Mexico, and for the economic, cultural, and ecological consequences their decline may bring.

“We used a bioenergetic model to simulate how oysters use energy to grow and reproduce,” says oyster expert Romain Lavaud, Assistant Research Professor at Louisiana State University Agricultural Center. “We wanted to predict, with the data and climate models we have right now, the production capacity of oysters in the current situation and in potential future climates.”

The research team learned that although nearly all climate models agree that the Gulf of Mexico will get warmer, the higher temperatures wouldn’t necessarily be a problem for oyster reefs. Because oysters can’t move, they are surprisingly amenable to a broad range of water conditions, even particularly warm or salty ones. However, the researchers discovered that another climate change effect had a much larger impact: precipitation variability. Climate models predict that rainfall may become more extreme across the Gulf of Mexico – fewer but larger storms, stronger hurricanes, worn-down barrier islands and beaches leaving coastlines exposed. And it is these extremes that threaten oysters most – the “killing floods” that sweep too much freshwater into the estuaries, or the hurricane-induced storm surges that wash in saltwater predators.

The research team created high-resolution maps of coastal Louisiana to Texas, showing how future conditions may impact current oyster populations. These maps revealed the complex decision space surrounding oysters. For example, their models indicate that oyster reefs grow more slowly in Texas, but Louisiana experiences more “killing” extreme events. Although they do not provide easy answers, the maps can help managers understand the tradeoffs that come with restoring oyster reefs or establishing new aquaculture beds along different coastlines.

“Oysters are part of our culture,” says Vincent Brown, Assistant Professor of Research at Louisiana State University. “If we can help identify future sites where oysters might thrive, that will help build resilience in those communities.”

Oyster farming is both delicious and lucrative, contributing hundreds of millions of dollars to the U.S. economy each year and driving tourism to coastal communities. Simultaneously, oyster reefs are critical components of coastal ecosystems, helping to keep water clean, protecting shorelines from waves and storms, and providing shelter for young fish and crustaceans.

Conserving ecosystems and maximizing oyster harvests can be in conflict, as wetlands restored to their original flood schedules contain more fresh water and thus produce less salty (and less delicious) oysters. Yet the researchers hope that, with their tool and more refined projections for future conditions, Gulf Coast communities will be able to identify ideal locations for both to balance economic and environmental goals.

The ONB features articles from Cooperative Fish and Wildlife Research Units across the country. Working with key cooperators, including WMI, Units are leading exciting, new fish and wildlife research projects that we believe our readers will appreciate reading about. This work was led by Megan La Peyre, Research Fish Biologist with the USGS Louisiana Cooperative Fish and Wildlife Research Unit; Barry Keim, the Director of the Environmental Health, Climate, and Sustainability Program at the School of Public Health at the LSU Health Sciences Center in New Orleans; Jennifer Pollack, McKinney Endowed Chair for Coastal Conservation at the Harte Research Institute, and Brady Couvillion, Geologist with the USGS Wetland and Aquatic Research Center. Funding was provided by the USGS South Central Climate Adaptation Science Center.