Have You Thanked an Oyster Today?

“Credit for aquaculture oyster floats.”

Filling out my tax return is usually a pretty mundane activity, but this phrase piqued my interest as I worked through the Maryland portion of the form. Sure, seafood is a local delicacy, and the Chesapeake Bay is an iconic part of living in this area, but why would the state subsidize floats — aquatic gardens — for residents to cultivate oysters on private piers? The answer surprised me — and convinced me that this humble bivalve is deserving of some seriously overdue appreciation. Whether enjoying the beauty of the Chesapeake, frolicking in its waters or sampling its delicious harvest, Marylanders have oysters to thank. And reviving the bygone era of oyster abundance could bring untold benefit to the local economy and environment.

Molluscan Heroes

Oysters’ filter feeding abilities have earned them a nickname: the livers of our rivers. A single oyster can filter over 50 gallons of water per day. Nitrogen and phosphorous from industrial waste and agricultural runoff are triggers for deadly algae blooms, but oysters consume these pollutants and use them to build their shell. While they’re at it, they remove particles from the water column and propel them to the seafloor, improving clarity and light penetration, which promotes seagrass growth. In turn, seagrass provides food and shelter to other organisms. Oyster reefs — the massive structures that form when oysters settle and live on other oysters’ shells —  create shelter for small invertebrates and fish larvae, allowing a vibrant ecosystem to thrive. All of these features are what make oysters powerful keystone species, meaning they provide an outsize benefit to their ecosystem.

As if that wasn’t enough, oysters also play starring roles in the Earth’s carbon cycle. Their service to marine ecosystems can bolster aquatic vegetation, which absorbs carbon dioxide through photosynthesis. They also build calcium carbonate shells — protective homes that store carbon. Although cutting fossil fuel emissions is mandatory to mitigate the dangerous impacts of climate change, shellfish restoration and aquaculture are among many potential ancillary strategies that are receiving increased attention. Another benefit from oysters is especially important in a warming climate: Oyster reefs provide a physical barrier that dissipates wave energy, protecting coasts from erosion and flooding caused by increasingly severe storms.

An Ecosystem in Peril

When Europeans reached the Chesapeake in the 17th century, oysters were so abundant that their reefs posed a navigational hazard. But this once ubiquitous population has since fallen to a measly 1% of historic levels. The collapse is among the largest recorded declines of marine species.

The downturn began in the 1800s, when fishing practices became industrialized. The use of hand tongs, which likely had minimal impact on the oyster reef structure, was replaced by dredging, a method in which mesh scoops made of metal are dragged across the seabed. The practice had destructive impact on the structural integrity of centuries-old oyster reefs. Oyster catch peaked at 600,000 metric tons in 1884 and plunged soon after, signaling a precipitous drop in oyster abundance.

Today, what is left of the population faces considerable challenges. After disturbance of the solid substrates that oysters need to survive, viable habitats are more limited. Additionally, habitat destruction may have left oysters more susceptible to parasitic diseases, which became increasingly problematic in the 20th century. Finally, increased carbon emissions are causing atmospheric carbon dioxide to dissolve in the seas and increase their acidity, which could impair mollusks’ ability to build their shells.

Bringing Oyster Back

As dispiriting as this state of affairs may seem, recent developments inspire hope and portend a resurgence in oyster love. In 2010, Maryland passed legislation aimed at reviving oyster populations. The plan increased the proportion of oyster habitat set aside as sanctuaries, which are off limits to harvesting, from 9% to 24%.

The bill also expanded areas available for oyster aquaculture leases, which became legal in the state in 2009. Soon after, Maryland began offering subsidized loans to upstart oyster farmers. The two-pronged approach aims to protect wild oyster habitat while supporting a burgeoning aquaculture industry that stimulates the local economy and provides a remarkably sustainable food source.

Multiple organizations, including the Oyster Recovery Partnership, the Chesapeake Bay Foundation and the Chesapeake Oyster Alliance, are hard at work as they push to restore protected reefs to their former glory. The programs recycle shells from restaurants and local drop-off sites, and use them as substrates to cultivate newly spawned oyster larvae, which are subsequently planted on sanctuary reefs. Millions of oysters are being added to the bay each year, and the efforts are receiving a boost from volunteers who help the initiative capitalize on underused waterfront space. Through oyster gardening programs, Marylanders can receive seed oysters and raise them off of private piers, then return the fully grown critters to be added to a protected habitat. It’s just one of many ways that locals can join the effort.

Spreading the word, volunteering, recycling shells and buying locally farmed oysters are all ways to be a part of the oyster revival. After all, among oysters’ many amazing qualities, one is almost impossible to ignore: their deliciousness.

References

1. Barnett, C. The Sound of the Sea — Seashells and the Fate of the Oceans. (W.W. Norton & Company, 2021).
2. DePiper, G.S., Lipton, D.W. and Lipcius, R.N. “Valuing Ecosystem Services: Oysters, Denitrification, and Nutrient Trading Programs.” Marine Resource Economics. 32, 1–20 (2017).
3. “Inside Efforts to Restore the Chesapeake Bay’s Oyster Population.” CBS This Morning Saturday (2021). https://www.cbsnews.com/news/chesapeake-bay-oysters-maryland-restoration/
4. Dominic McAfee, Ian McLeod, Maria Vozzo and Vivian Cumbo. “The Surprising Benefits of Oysters (and No, It’s Not What You’re Thinking).” The Conversation (2018). https://theconversation.com/the-surprising-benefits-of-oysters-and-no-its-not-what-youre-thinking-90697
5. Alexandra Herr. “How Oysters and Seagrass Could Help the California Coast Adapt to Rising Seas.” Salon (2021). https://www.salon.com/2021/06/20/how-oysters-and-seagrass-could-help-the-california-coast-adapt-to-rising-seas_partner/
6. Michael E. Mann. “Global Warming.” Britannica. https://www.britannica.com/science/global-warming
7. Lee, H.Z.L., Davies, I.M., Baxter, J.M., Diele, K. and Sanderson, W.G. “Missing the Full Story: First Estimates of Carbon Deposition Rates for the European Flat Oyster, Ostrea Edulis.” Aquatic Conservation — Marine and Freshwater Ecosystems. 30, 2076–2086 (2020).
8. Rachel Lovell. “The Simple Food That Fights Climate Change.” BBC. https://www.bbc.com/future/bespoke/follow-the-food/the-simple-shellfish-that-fights-climate-change.html
9. “History of Oysters — The Rise and Fall of a Key Chesapeake Bay Species.” University of Maryland Center for Environmental Science. https://www.umces.edu/oysters/history
10. B.J. Rothschild, J.S. Ault, P. Goulletquer and M. Héral. “Decline of the Chesapeake Bay Oyster Population: A Century of Habitat Destruction and Overfishing.” Marine Ecology Progress Series. 111, 29–39 (1994).
11. James B. Hale. “O’Malley Announces Drastic Changes to State’s Oyster Industry.” Southern Maryland Online. (2009). http://somd.com/news/headlines/2009/10922.php
12. Rona Kobell. “Aquaculture Reviving Md. Oyster Industry — As Well As Watermen.” MarylandReporter.com. (2017). https://marylandreporter.com/2017/06/29/aquaculture-reviving-md-oyster-industry-as-well-as-watermen/
13. CBF Adds 14 Million Oysters to Chesapeake Bay in Maryland in 2020. Chesapeake Bay Foundation Press Release. (2021). https://www.thebaynet.com/articles/0221/cbf-adds-14-million-oysters-to-chesapeake-bay-in-maryland-in-2020.html

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