Bo Lusk collects eelgrass shoots during a seagrass restoration project in the South Bay of the Virginia Coast Reserve. Image credit: Daniel White/TNC
(Ahead of World Oceans Day this Saturday, June 8, Cool Green Science is running posts this week looking at the science and issues of marine restoration. Here’s more information on Restoration Week and what the Conservancy is doing to restore marine habitats such as coral reefs, eelgrass, shellfish, and mangroves.)
Eelgrass and shellfish restoration programs are among the most successful in The Nature Conservancy’s marine portfolio. To get a clearer picture of the state of eelgrass and shellfish restoration science, I asked Bo Lusk, marine steward with The Nature Conservancy’s Virginia Coast Reserve program, to respond to two questions — what science do we need to accelerate the impact of sea grass and shellfish restoration, and what science do we already have that needs to be applied more widely. –Bob Lalasz
What are the critical science gaps for eelgrass restoration? What don’t we know that, if we knew it, could really make a difference for people and nature?
Eelgrass and excess nitrogen: We’re fortunate in how much science we do have that’s allowed us here in the Virginia Coast Reserve to make this the largest sea grass-restoration project in the world. With the expertise of the Virginia Institute of Marine Science (VIMS) and the Virginia Coastal Zone Management Program (VCZMP), our partnership is able to demonstrate a lot of the science that can help restore eelgrass elsewhere.
In other places such as Long Island Sound, where eelgrass restoration is not having quite such an easy time of it, our colleagues have done a good job of identifying inputs into the Sound — mostly excess nitrogen from septic — that are inhibiting eelgrass recovery in some locations. They’ve been developing a model to try to figure out where restoration up there will work and where it won’t.
Eelgrass diversity and restoration methods: At the Virginia Coast Reserve, we’re fortunate that we’ve got a relatively unspoiled section of the coast, so it’s a great living laboratory for this research. The University of Virginia has already done some work on our eelgrass genetics and found that the restoring eelgrass through seed dispersal — as opposed to planting plugs, the more traditional restoration method — helps to maintain genetic diversity, which makes the sea grass meadows more resilient. We need to keep building on that.
Our success at the Reserve with eelgrass isn’t limited to just the plots that we’ve planted. We’ve planted fewer than 400 acres of grass so far — starting from literally zero acres — and now the eelgrass is approaching 5,000 acres out there and causing a state change, in the right direction for once, in some of these seaside bays.
What we’ve found through examining light levels is that, once you get a certain amount of grass out there, you start getting a positive feedback loop. It starts clearing its own water: It prevents the re-suspension of sediments, it filters some sediment out of the water, and it dampens wave action.
And all of those qualities tend to keep the water clearer around it, which is good for the grass and helps the grass to suddenly explode and spread on its own, as well as keeping sediments from filling up our navigable waterways; it prevents some of the dredging projects we might have to pay for in the future. It also keeps hard substrates available for oyster restoration by keeping the sediment off of those substrates. So just physically, the grass is making the water clearer and allowing more light to get down, so the grass continues to spread on its own.
What known science do we have that needs to be applied more widely that would make a critical difference using eelgrass for coastal ecosystems?
The benefits of ocean inlets: We know that if you’ve got enough seeds, using seed dispersal to restore eelgrass can be a really good technique. And we know that by using seed dispersal, we are maintaining genetic diversity, so we’re going to have more resilient sea grass meadows in the future.
We also are seeing that the nice, clear, cool water that comes into bays from all of our ocean inlets is really having a good effect at tempering the hot water temperatures that we see in the summer, and it helps the grass be more productive throughout the summer.
So the science tells us that, if an ocean inlet opens up, say, somewhere on the Outer Banks of North Carolina or through another barrier island, it really can do a world of good for the sea grasses in the bays and lagoons behind those barrier islands — which, in turn, can really benefit their ecosystems.
It’s just a matter of generating the political will to let these inlets stay open rather than filling them in and building a highway back over them. That might be impossible in many cases, but if people understood a little more about how this stuff works, we might have a chance at keeping some of those inlets open.
The ecological function benefits of eelgrass: One of the most amazing things that’s happened here in Virginia is the promising return of the bay scallop. When we lost all of our eelgrass in 1933 [after a Category 1 hurricane wiped out the state's diminished stock, already hit by disease], we lost all of our Virginia bay scallops and our bay scallop industry along with them.
A couple of years ago, we got funding in partnership with the VIMS to start figuring out how to reintroduce the bay scallop to Virginia, and we found that we have large enough eelgrass meadows dispersed spatially around the Virginia Coast Reserve that when we put cages of scallops out in our grass beds, they spawn, and their offspring are actually recruiting into these restored meadows. So not only are we able to get grass itself out there, but it’s functioning as the ecosystem these bay scallops need to survive.
Eelgrass is tremendously beneficial for not just commercial fishing industries, for our blue crab harvest, but also for our recreational fishing industry. This grass is fantastic habitat for sport fish or for the prey that sport fish like to feed on. It’s potentially good for the waterfowling industry and for birdwatchers — we’re seeing large numbers of brant, which is a waterfowl that used to feed almost exclusively on eelgrass, starting to return to the area to feed on these grass beds.
Finally, both eelgrass restoration and oysters have been shown to fight against ocean acidification. We’re seeing increased acidities in a lot of our coastal waters, which can be really tough on our clam and oyster aquaculture industry, which is big money around here. So by doing this restoration, we’re helping to buffer some of that acidity, just by getting thousands of acres of eelgrass out there, or as many acres of oyster shells out there as we can.
All these benefits are known, but not widely enough. Eelgrass is native to the US East Coast from North Carolina northward.
For shellfish restoration, we have a lot of science — but where could our findings really make a difference if they were fully applied?
There are a lot of places where we could get oyster restoration done, and where oyster restoration has even been successful, but government policies and regulations have made us actually pull up oysters that we’ve had growing.
This happens in areas like Delaware and New Jersey, where you’re not allowed to do oyster restoration in waters that are close to shellfish harvest, because authorities are afraid someone will steal the oysters that we put in, and that someone will eat those oysters and get sick, thereby hurting the rest of the shellfish industry in those states.
I understand that fear. I grow clams myself, and every time there’s a story on the news about somebody getting sick from eating shellfish, our prices drop, and I’m not making as much money off of my clams.
On the other hand, these sorts of places are precisely where we need to be doing oyster restoration. If you’ve got an impaired body of water, science tells us that getting a bunch of oyster reefs growing there will help to clean up that water.
So we need to be able to do oyster restoration in places that need oyster restoration. And we need to enable law enforcement to have the capacity to be able to keep poachers out of those areas so we don’t have to worry about somebody stealing oysters from restoration sites and we don’t have to worry about somebody eating those oysters and getting sick.
Opinions expressed on Cool Green Science and in any corresponding comments are the personal opinions of the original authors and do not necessarily reflect the views of The Nature Conservancy.