Can they have it all?
Around Chesapeake Bay, just about everyone agrees: oysters are tasty and seagrass is important. Supporting shellfish that underpin a multi-million dollar aquaculture industry and seagrass that provide habitat for fisheries sounds like a no-brainer, but there’s a hitch—these equally beloved resources thrive in the same places. This makes deciding which to support a challenge for coastal resource managers. But what if the same spot could support both?
That’s a question Erin Shields, lead scientist at the Chesapeake Bay Reserve in Virginia is helping to answer, in partnership with the Virginia Institute of Marine Science and commercial oyster growers, and with the help of state funding.
“We want to know if oyster aquaculture can coexist with Submerged Aquatic Vegetation (SAV) like seagrasses,” says Shields. “In recent years, we have seen seagrasses expand into existing aquaculture farms, suggesting that they can coexist, but we do not know whether the seagrasses within aquaculture sites are as healthy as they would be in the absence of aquaculture.”
Large seagrass declines in the 1970s, caused by storms and pollution, drew attention to the importance of the Bay’s seagrass, not only for fisheries habitat, but also as an indicator of water quality. Millions of dollars and decades of collaboration have gone into water quality improvements and seagrass restoration, with some success.
At the same time, oyster aquaculture has also expanded. To balance the needs of growers with a responsibility to protect the health of seagrasses, Virginia currently only permits aquaculture in areas where no seagrass has grown in the past five years. Whether this approach is too cautious is hard to know, given that the impacts of farming practices on seagrass have not been studied and data to make a more informed decision does not exist.
To address this need, Shields and her collaborators chose to start by studying farms growing oysters in floating cages. As part of the project, two growers established commercial-scale farms in the water column above existing seagrass beds. Like other plants, seagrass needs light to thrive, but through careful spacing and movement of the cages by tides and winds, shading impacts of floating cages are reduced.
“If we find that floating oyster aquaculture has little or no impact on underlying seagrass beds, we will expand our studies to encompass a broader geographic area and more types of aquaculture gear,” says Shields. “If we find that floating oyster aquaculture does have negative impacts on seagrasses at our study sites, we will work with growers to develop best management practices to reduce or eliminate these impacts.”
“The is very exciting research that has a high probability of identifying best management practice that will support the expansion of oyster aquaculture and our goals of conserving valuable seagrass beds in Chesapeake Bay,” says Mark Luckenbach, professor and associate dean of Research & Advisory Service at the Virginia Institute of Marine Science.
Now in its fourth season, the project will continue into the foreseeable future, testing these adapted approaches at different sites with new collaborators.