Native oysters once again in the spotlight
“Oysters ‘r’ in season.” That old folk wisdom that oysters are in season during the months that have the letter ‘r’ in them—from September to April— is based on a scientific fact. Oysters in the Chesapeake eat heartily during the warm, late summer months, and their total biomass peaks in the September to November period.
Our scientific interest in oysters seems to be peaking, too, based in part on an intriguing set of findings released earlier this summer by Carl Cerco. A well-respected researcher from the Army Corps of Engineers, Cerco has run a series of computer simulations in which he has been able to estimate various ecological benefits that accompany oyster restoration.
According to Cerco, increasing the native oyster biomass by 25-fold would result in significant reductions in harmful nitrogen and chlorophyll a. Similarly, it would push up healthy dissolved oxygen levels and improve water clarity.
Oysters at this level of abundance, which mirrors levels found in the Bay in 1920-70, would remove millions of pounds of excess nitrogen.
The improvements, which are especially noticeable in the areas immediately adjacent to healthy oyster reefs, could result in a 20 percent increase in vital underwater Bay grasses.
We now know more precisely than ever the essential role that oysters play in the health of the Bay ecosystem.
But oysters are at just 1 percent of their historic abundance, and they are providing few of the ecological benefits that Cerco details. So in addition to good research, we need to focus on restoration strategies. Thankfully, there’s plenty to focus on, ranging from oyster breeding programs to large-scale restoration projects.
Stan Allen of the Virginia Institute of Marine Science and his colleagues at three other mid-Atlantic universities have been working to strengthen our oyster populations. Years of painstaking effort have resulted in a new strain of native oyster that is especially resistant to the two diseases that have ravaged the local bivalve.
At the University of Maryland’s Center for Environmental Science Horn Point Lab, a huge, industrial-level oyster hatchery is operating full time. Dr. Donald Meritt is leading an effort by UMCES and Sea Grant Extension Program scientists to grow literally millions of disease-free native oysters. More than 400 million young oysters have been raised at the lab and are being used in projects across the watershed.
The Chesapeake Bay Foundation, the powerful education and advocacy group, is working on a completely different approach. It has an intriguing effort under way in which specially bred sterile native oysters have been delivered to Virginia aquaculture farms to be raised for market.
Will these native oysters—spared the stress and energy demands of natural reproduction—quickly grow to market size?
These various breeding programs are being integrated into restoration projects.
In Virginia, more than 100 reef sanctuaries have been started in recent years. Most are small, but all are providing important clues about how to jump-start the native oyster restoration effort.
In an impressive partnership, researchers from the National Oceanic and Atmospheric Administration, VIMS, the Virginia Marine Resources Commission and the Army Corps of Engineers have identified the most promising substrate as well as the best size and dimensions for new oyster reef construction.
The non-profit Oyster Recovery Project is showing encouraging results with the Horn Point oysters at its 33 project sites in Maryland waters. From the Terrapin Sands site near the Virginia line to the Memorial Stadium site near Tolchester in the Upper Bay, these efforts are excellent examples of cooperative conservation in action. Operational partners include NOAA, the Army Corps, the state Department of Natural Resources and the Maryland Watermen’s Association.
A first-of-its-kind effort in Virginia’s Great Wicomico River will be concluding its initial phase this month. More than 15 million disease-resistant native oysters have been planted in this Northern Neck tributary, the largest such effort undertaken in the Chesapeake, and perhaps the biggest of its kind anywhere.
Scientists, watermen, environmentalists, government officials and seafood lovers alike are guardedly optimistic about all these efforts. As researcher Cerco notes, oysters play such an essential role in the ecology of the Bay that many of us believe their success is a mandatory element of any effective Bay restoration strategy.
Ironically, a significant push behind this recent flurry of activity has been the state of Maryland’s quest to introduce the non-native oyster, Crassostrea ariakensis, into the Bay. The controversial proposal has alarmed many scientists and others who are concerned about the potential negative effects of bringing this species into the fragile Bay ecosystem.
Before the state can put the foreign oyster into the Bay, though, it must first thoroughly analyze prospects for the restoration of the native oyster, C. virginica.
With significant funding from NOAA and Maryland, as well as the Army Corps of Engineers and various Virginia entities, a number of important research efforts are in full swing. Cerco’s study is part of that effort as is a very different analysis done earlier this year by Michael Paolisso, an anthropologist from the University of Maryland College Park.
Paolisso conducted a series of interviews to try to better understand the social and cultural importance of oysters to the people who live, work, recreate, study and make their living on the Bay. Not surprisingly, opinions among these diverse stakeholders varied widely.
But he was able to tease out an important finding: that the oyster is changing roles in the Bay. The perception of oysters as a food/industry is shifting to its being a powerful provider of ecological services—exactly the effects that Cerco documented in his work.
Importantly, Paolisso also found that people in the Chesapeake region remain optimistic that given time and resources, native oyster restoration might yet be successful.
Our experience with another shellfish, the dark false mussel, suggests that such optimism might be warranted. In spite of its negative-sounding name, this tiny bivalve is a native species, and it is having an extremely positive effect in some sections of the Bay.
The mussel made its presence known last summer in a number of upper tributaries. Breeding in prolific numbers in places like the Magothy River, the dark false mussel population boom was accompanied by remarkable improvements in water clarity as these organisms cleared the water column of excess nutrients and harmful algae.
This year, scientists are reporting that the species is back and again having a profoundly beneficial effect on local waters. What’s more, they are seeing improvements in Bay grasses, including the return of some species not seen in these waters for many years.
It would appear that we have finally reduced excess nutrients enough to give these tiny organisms an ecological foothold. Combined with the fact that they are spared any harvest pressure, these shellfish are thriving. In so doing, they are accelerating water quality and habitat improvements in a happy, positive feedback loop.
Will a restored native oyster population similarly be able to bring its remarkable filtering capacity back to the aid of the Bay? An extraordinary coalition of state, federal, academic, non-profit and private interests is working overtime this fall to find out.
Because during this critical juncture of Bay restoration, oysters ‘r’ definitely in season.
Comments are now closed for this article. Comments are accepted for 60 after publication.