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SEA Currents Blog

SEA Currents: Corwith Cramer


May 15, 2021

Using East Coast Case Studies to Explore Oyster and Eelgrass Restoration in the Chesapeake Bay

Kass Wojcik, Sydney-Marie Jones & Laurens Vermuelen, Bryn Mawr College, Carleton College & University of Central Florida

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SSV Corwith Cramer (file photo)

During the first week of May, we crossed from the warm waters of the Gulf Stream in the Southeast Large Marine Ecosystem into the colder, more productive waters of the Northeast Large Marine Ecosystem (LME).  As we passed the mouth of the Chesapeake Bay-an enormous estuary just north of the border between the two LMEs-the difference between the two environments became obvious.  Where the air of the Southeast LME had been steamy and the water a deep royal blue, the air of the Northeast LME was now crisp, with the faint smell of pine, and the sea a soft green.  One day people were wearing shorts and t-shirts, and the next the deck was a sea of neon colors as people broke out their foul weather gear to brace against the chill.  It was fascinating to be able to see our transition into the Northeast LME so clearly, and as we passed the Chesapeake Bay, we were reminded of some of the important ecosystems and fisheries this LME supports, namely oysters. Overfishing combined with loss of habitat due to poor water quality and increasing temperatures has created population collapses within wild oyster fisheries all along the East Coast. The Chesapeake Bay is no exception, and it has had a long and complicated relationship with oyster harvesting as well as a history of failed oyster restoration projects and habitat management.

The Chesapeake began to first experience significant habitat loss and oyster declines when the southern oyster industry began to take off in the mid-1800s after the collapse of New England fisheries drove industrial fishing south. By the 1850s, the Chesapeake was already experiencing heavy environmental degradation and overexploitation, which in turn created significant declines in oyster populations during the 1880s. By the 1920s, early conservation efforts to restore oyster populations began with oyster shell plantings and larvae seedings. At the same time, the number of private leaseholders began to surpass public fisheries, masking much of the overfishing, habitat degradation, and disease outbreaks that were occurring. The public fishery collapsed not long after, followed by the private fishery in the mid-1980s.  The collapse of the private fishery was largely a result of disease outbreaks attributed to warming waters. Perkinsus marinus is a native fungus that started causing adult oyster mortality in the 1940s, increased in the 1980s, and is still a problem today, although it has since declined in severity. Haplosporidium nelsoni is another oyster disease that was introduced into Delaware Bay from Pacific oysters in the 1950s.  The two diseases are estimated to have caused between 90 and 95% of oyster mortality in the high salinity waters of the Chesapeake Bay, which led to further overfishing as fishermen raced to harvest as many as possible before they died.

Today, oyster habitat in the Chesapeake is considered to be poor and oyster stocks are low.  The oyster fishery is defined as collapsed, largely as a result of overfishing and disease as well as poor stock management. Restoration efforts have increased over time, however studies show that repletion programs in the Chesapeake Bay have been largely ineffective, both in terms of cost and success.

For our Conservation and Management project, we’re interested in exploring why the oyster restoration efforts in the Chesapeake have been so ineffective and how they can become more successful by examining examples of oyster restoration along the East Coast and applying some of those most effective principles to the Chesapeake.  In Florida, oyster population have been declining for similar reasons as in the Chesapeake-namely habitat destruction, over-harvesting, and parasites such as the boring sponge. Rather than tackling oyster restoration alone, however, repletion efforts in this area have been paired with mangrove and coastal grass (Spartina alterniflora) restoration in order to take advantage of the symbiotic relationships between the species.  Mangroves and coastal grass beds can improve water quality through filtration and erosion prevention as well as provide habitat for oysters.  A similar strategy can potentially be employed in the Chesapeake by seeding eelgrass, a species of seagrass found all along the East Coast.  Like mangroves and Spartina alterniflora, eelgrass can improve water quality as well as provide critical habitat for oyster and fish.  Additionally, as oysters have declined in the Chesapeake, eelgrass too has decreased significantly-largely due to poor water quality-which is why restoring both together could be an effective strategy for improving Chesapeake water quality and estuarine habitats.  Large scale eelgrass seeding in Virginia coastal lagoons and biodegradable grid plantings in Maine have resulted in extensive eelgrass bed restoration, and we’re interested in exploring if similar strategies could be applied to the Chesapeake in order to restore the eelgrass there and potentially provide habitat for shellfish like oysters.

Protecting and restoring oysters and their habitat is critical, and as we work on our policy project, we’re interested in seeing how we can use case studies from other areas to improve Chesapeake oyster restoration strategies that have been largely unsuccessful up to this point. While oysters are considered to be critical keystone species due to their ability to filter water, serve as a habitat for young fish species, and strengthen coastline ecosystems by preventing erosion and lessening storm destruction, they heavily rely on other species such as eelgrass for their survival.  This is why focusing on community restoration rather than the repletion of a single species as has been done in areas like Florida and Maine may be a more effective strategy for oyster restoration in the Chesapeake. While it will be an extremely difficult process, it’s our hope that one day you will be able to look out into the Chesapeake Bay and see miles and miles of seagrass and oyster beds overlaid by beautiful clear water as you once could.

Sources
Groner, Maya L., Colleen A. Burge, Ruth Cox, Natalie D. Rivlin, Mo Turner, Kathryn L. Van Alstyne, Sandy Wyllie‐Echeverria, John Bucci, Philip Staudigel, and Carolyn S. Friedman. 2018. “Oysters and Eelgrass: Potential Partners in a High PCO2 Ocean.” Ecology 99 (8): 1802-14. https://doi.org/10.1002/ecy.2393. Kidder, George W., Shannon White, Molly F. Miller, Wendy S. Norden, Theodore Taylor, and Jane E. Disney. 2015. “Biodegradable Grids: An Effective Method for Eelgrass (Zostera Marina) Restoration in Maine.” Journal of Coastal Research 31 (4): 900-906. Orth, Robert J., Jonathan S. Lefcheck, Karen S. McGlathery, Lillian Aoki, Mark W. Luckenbach, Kenneth A. Moore, Matthew P. J. Oreska, Richard Snyder, David J. Wilcox, and Bo Lusk. 2020. “Restoration of Seagrass Habitat Leads to Rapid Recovery of Coastal Ecosystem Services.” Science Advances 6 (41): eabc6434. https://doi.org/10.1126/sciadv.abc6434. Orth, Robert J., Scott R. Marion, Kenneth A. Moore, and David J. Wilcox. 2010. “Eelgrass (Zostera Marina L.) in the Chesapeake Bay Region of Mid-Atlantic Coast of the USA: Challenges in Conservation and Restoration.” Estuaries and Coasts 33 (1): 139-50. https://doi.org/10.1007/s12237-009-9234-0. Shulte, David M. “Frontiers: History of the Virginia Oyster Fishery, Chesapeake Bay, USA. Marine Science. n.d. Accessed May 9, 2021. https://www. frontiersin.org/articles/10.3389/fmars.2017.00127/full.

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