Harris Creek was once home to nearly 1,500 acres of Maryland’s best oyster reefs, but in recent decades its oyster population — like those in much of the Bay — had dramatically dwindled. When biologists surveyed the creek a few years ago, “we barely found an acre that was functioning at what we would consider the historic level,” said Stephanie Westby, oyster project coordinator with National Oceanic and Atmospheric Administration Chesapeake Bay Office.
In fact, only a few hundred thousand oysters remained. With few oysters to rebuild them, the reefs had deteriorated.
In short, Harris Creek looked like much of the rest of the Chesapeake, where oyster numbers are estimated to be at 1 percent or less of their historic abundance.
That was then.
Today, biologists hope Harris Creek looks more like the Bay’s future than its past.
Thanks to an investment of more than $25 million since 2011, the addition of more than 300,000 cubic yards of rock and other reef building substrate, and more than 2 billion hatchery-reared baby oysters, Harris Creek is home to more than 350 acres of oyster reefs.
That level of restoration is “unprecedented,” said Peyton Robertson, director of NOAA’s Chesapeake Bay Office. “We haven’t done anywhere near that scale.”
Neither has anyone else. The more than 350 acres of oyster reefs constructed in Harris Creek makes it not only the largest oyster restoration project in the Bay, but in the world.
On Sept. 15, officials from state and federal agencies and nonprofit groups supporting the effort gathered on the creek, located on the north shore of the Choptank River for the planting of the final seed — hatchery-reared oyster spat attached to oyster shells — on the reef.
The ceremonial event involved the Maryland Department of Natural Resources, NOAA, the Army Corps of Engineers, the University of Maryland Center for Environmental Science and nonprofits such as the Oyster Recovery Partnership, The Nature Conservancy and the Chesapeake Bay Foundation. All had in some way been involved in the restoration.
The project was the realization of new thinking that suggests the old approach to oyster restoration, where a few acres of oyster reefs were scattered here and there, would never return the bivalves to their past abundance, a time when towering reefs rose above water level in some places and oysters were so plentiful they could filter a volume of water equivalent to the entire Bay in a matter of days. Today’s population takes about a year to do that job.
The former small projects, biologists say, were not enough to change the overall trajectory in which the Bay lost reef habitat faster than oysters could build it. Maryland alone has lost about 80 percent of its oyster bar habitat in just the last quarter century.
The new large-scale strategy seeks to rehabilitate the majority of remaining potential reef habitat in an entire tributary. Harris Creek had about 600 acres of potentially restorable habitat when the project started. The hope is that large reefs will reach a tipping point where oyster populations not only become self-sustaining, but also expand their reefs, improve water quality and provide habitat for other species.
“This is something I have always been pretty passionate about — wanting to see oysters come back,” Robertson said. “That feels really good, to feel like we’ve actually gotten a big job done that affords the potential to do something outstanding in the long run.”
Harris Creek will not keep its “largest ever” title long. An even larger restoration effort is under way in the nearby Little Choptank, a tributary on the Choptank River’s southern shore, that will eventually total 440 acres.
In addition, work in five other Bay tributaries is moving forward as part of an effort to meet a Chesapeake Bay Watershed Agreement goal of restoring oyster populations and habitats in 10 tributaries by 2025.
While construction is complete, it’s premature to call Harris Creek a biological success. “It’s like a ribbon cutting at a hospital,” Westby said. “You built the hospital, you spent a lot of money, but you haven’t saved any lives yet. That’s kind of where we are at with Harris Creek.”
Under criteria adopted by the Bay Program, a determination of restoration success can’t be made for six years, at which time the reefs need to have a minimum of 15 oysters per square meter, with 50 being the target. The oyster population has to consist of at least two, year classes, so the goal can’t be met on the basis of a single good year of reproduction. And, the total reef area has to be stable or increasing in size.
Biologists will start getting an indication of how Harris Creek is faring when follow-up monitoring begins later this year on some of the first reefs constructed at the site. Scattered studies in the last few years have yielded positive signs. Early work, for instance, suggests oysters in Harris Creek have twice the survival rate of oysters in past restoration projects in Maryland, and there have been some hints that oyster reproduction has increased.
“We are seeing positive results, which suggests everything is going well,” said Angela Sowers, of the U.S. Army Corps of Engineers Baltimore District. “Getting started is often the hardest part, but we’ve gotten off to a great start and we are figuring out how to do it.”
But a lot could happen in coming years. A prolonged drought could cause the resurgence of lethal oyster diseases, which have been on the decline in recent years. Weather conditions may not be favorable for reproduction, which is needed to help sustain the population. And, a growing population of mature oysters could become a tempting target for poachers.
If parts of the restoration project appear to be faltering, biologists may seek to intervene and do more work in coming years.
Ideally, biologists are looking for more than just abundant oysters. They want to see evidence that their reefs are kick-starting the local ecosystem. Are they measurably improving water quality, as scientists believe they will? And, are the reefs providing habitat that increases populations of crabs and fish? Are they helping the recovery of underwater grasses?
Scientists are also working to quantify the extent to which oyster larvae produced in Harris Creek helps to repopulate nearby parts of the Choptank River. “A lot of those areas are open to the commercial fishery, so the hope is that this sanctuary will not only reseed itself, but have some benefits for the fishing community by increasing [oysters] in the harvest areas,” Westby said.
Work in Harris Creek and on other projects is also providing insights about how the costs of future projects can be reduced. For instance, a recent study found that using a thin layer of oyster shell on top of other material is as beneficial for attracting oyster larvae, or spat, as building a whole reef of shell. This may not only reduce construction costs but conserve hard to acquire shell.
“We want to maximize the coverage of the limited amount of shell that we have across sites,” Sowers said.
The Maryland Department of Natural Resources resorted to purchasing fossil oyster shell from Florida to meet the demands for shell on the Harris Creek and Little Choptank projects.
Biologists also learned that they could jump-start the oyster population in certain sparsely populated sites where they originally thought they would have needed to build reefs. Instead, they simply add more spat-on-shell — which is much less costly.
Those types of insights helped to reduce the cost of the Harris Creek project from early estimates of $31 million to around $25 million.
But the real payoff, biologists hope, won’t be measured in dollars, but in a healthier ecosystem.
“For the long-term health of the Bay, we have to have a filter feeder, and this is the dominant filter feeder,” Sowers said. “It is just so paramount to how the Bay functions. Being a part of trying to restore that piece of the puzzle to the Bay restoration is the fun part, but the work is very challenging.”