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Cleaning the Chesapeake’s Waters with Oyster Restoration

The Earth & I Interviews Karl Willey of the Maryland Oyster Restoration Center of the Chesapeake Bay Foundation

Oysters are deployed in the Lafayette River in Norfolk, Virginia, in 2015.   © Senator Tim Kaine/Wikimedia
Oysters are deployed in the Lafayette River in Norfolk, Virginia, in 2015. © Senator Tim Kaine/Wikimedia

Oysters have become recognized for their ability to clean water and their role in water ecosystems.

Organizations such as the Chesapeake Bay Foundation (CBF) in Maryland have been utilizing oysters for water restoration efforts, particularly in the Chesapeake Bay, America’s largest estuary.

Below are edited highlights from Gregg Jones’s interview with Karl Willey, center manager of the Maryland Oyster Restoration Center of the Chesapeake Bay Foundation, in which he discusses the role of oysters and that of his organization in restoring the Chesapeake Bay.

What is your role with the CBF (Chesapeake Bay Foundation)?

I am the Maryland Oyster Restoration Center Manager. With our oyster restoration coordinator, oyster gardening coordinator, four 3,300-gallon oyster growing tanks, and a sixty-foot oyster seeding boat, we engage hundreds of volunteers to help Save the Bay through oyster restoration activities.

At our oyster center, we can grow around twenty million to thirty million [oyster larvae] on shell per year and seed them out onto sanctuary reefs in the Chesapeake Bay and its tributaries. These oyster reefs are protected underwater and will never be harvested legally.

We also create Reef Balls with spat [juvenile] oysters on them and start a reef that didn’t exist. I call them “small condos,” with a spat-set of around 1,700 spats per Reef Ball.

What is a Reef Ball?

A reef ball’s a concrete sphere shaped like an igloo with holes in it. The holes allow fish to swim in and out of it, and it becomes an instant reef once you put spat on it.

A reef ball used in 2015.   © Office of Senator Tim Kaine/Wikimedia
A reef ball used in 2015. © Office of Senator Tim Kaine/Wikimedia

The third activity is oyster gardening. This involves growing several hundred spat-on-shell in cages the size of a mailbox and placing them off privately owned docks throughout Maryland and Virginia. Volunteers and our other partners will tend to the cages, cleaning them about once a month, and in the process see fish and critters on their own mini reef.

Spats in cages from an oyster gardening event on Nov. 5.   ©The Earth & I
Spats in cages from an oyster gardening event on Nov. 5. ©The Earth & I

The fourth activity is shell recycling by collecting oyster shells from restaurants and people that shuck at their homes. We provide locations for them to donate their shells, pick them up, stockpile them, and we set spat on them in our setting tanks by the next summer.

How big of a role does oyster gardening take in terms of the work that you do for reef restoration?

It’s a big and important role. It gets the word out to the public that oyster restoration is needed in the Chesapeake Bay. Growing oysters says “I care about the Bay and its critters” to our neighbors, lobbyists, and legislators. People are voting more for restoration work in the Bay and generally want to do more for Saving the Bay.

Getting people involved throughout the Chesapeake Bay Watershed in restoration work, whether it’s planting a tree or growing oysters, is a vital part of restoration. It helps us do our job in large-scale restoration efforts. Our volunteers educate our legislators that make political decisions allowing us to build more reefs in our public waters.

How long has CBF been involved with oyster restoration in relation to the Chesapeake Bay?

We started in 1996 with oyster gardening in Virginia and Maryland. It attracted donors as people saw how effective and exciting oysters are. Donors said they wanted to invest more money into restoration, so we slowly grew larger. CBF invested into a sixty-foot oyster seeding boat that we run named Patricia Campbell, named after donor Keith Campbell’s wife.

Historically, what would a natural, pristine oyster reef or tributary look like? What did they look like back in the 1600s before they were damaged by humans?

There are very few scriptures, writings, or logs from captains back then describing exactly what they looked like. They could describe them partially by saying that oysters were jetting out from the water at low tide, a ship could run aground on it, and you could eat your fill, and even after your fill, still see billions of oysters out there—a carpet of oysters.

Building up to that would be almost impossible today, but what we can do is start it by putting oysters on the bottom of the Bay, based on oyster reef charts done by the state of Maryland in 1905.

That’s where the partnership starts between nonprofits like the Chesapeake Bay Foundation and local, state, and federal agencies. The University of Maryland (UMD) and Virginia Institute of Marine Science (VIMS) scientists survey the bottom to find out where we could rebuild reefs. Then the Army Corps of Engineers and Maryland’s Department of Natural Resources (DNR) will place the substrate, whether it be shell, rock, or crushed concrete, on the bottom.

After putting the substrate down, other partners like the Chesapeake Bay Foundation and Oyster Recovery Partnership will seed the reefs with millions of spat-on-shell. Scientists later monitor the bottom and find out how it did. More than fifty adult oysters per square meter is considered a healthy oyster reef.

It may take a decade to get reef like hills underwater.

What you really need in a reef is a three-dimensional structure that would filter the Bay, provide habitat, and help break up the stratification in the water, allowing more oxygen to be pulled down from the top to the bottom, minimizing the dead zones in Chesapeake Bay that kill fish during the summertime. I think that is vitally important.

What you really need in a reef is a three-dimensional structure that would filter the Bay, provide habitat, and help break up the stratification in the water.

The second bonus you get out of the 3D structure of an oyster reef is that it breaks up big waves during storm events. Right now, we have a lot of shoreline erosion and land loss along waterfronts. Big catastrophic events like hurricanes can cause significantly more damage without the oyster reefs there to dampen down the larger waves.

Reefs play an important role in protecting fish and other critters, water quality, and shorelines.

Yes, there also isn’t much vegetation, right?

Right. If you have a hard shoreline, it makes it worse. A marsh or beach would look more natural and inviting in front of a home.

Oysters are analogous to the coral reefs in the Caribbean, the beautiful reefs you see when you go snorkeling in the blue water. All the fish live around it, but, once you swim away from it, you see very few fish by the sandy bottom. Life is similar in the Chesapeake Bay. Oysters are the Bay’s reefs. If you take all the oysters out of the Bay, then you just have sand and mud. There really isn’t much left in the Bay, thus making the oyster a keystone species. Without the oyster reef, many fish species would not exist in the Chesapeake Bay.

A rockfish, for example, loves rock. If you remove an oyster reef, which is oyster rock to some fish, a rockfish would be less likely to live there. They travel there to spawn but wouldn’t if it weren’t for the oysters. Other critters that live in the oyster reef are important, such as the oyster toad fish that lives on the bottom in an oyster reef with the goby, blenny, and skilletfish. There’s a long list of such species. And on the bottom under a reef there’s the benthic of organisms that benefit from the waste from oysters.

A skilletfish from the Rhode River in Maryland.  ©Smithsonian Environmental Research Center/Wikimedia
A skilletfish from the Rhode River in Maryland. ©Smithsonian Environmental Research Center/Wikimedia

Exactly how do oysters benefit the Bay?

When an oyster eats, it filters everything out of the water. It grabs all of it and filters it into its system. And it identifies what it doesn’t like and packages it up into a pseudo-feces and distributes it on the bottom where other organisms will consume it.

For algae and things it likes, the oyster will send them through its gut and digest them, which then becomes feces on the bottom that other organisms will consume. So, oysters clean the water column, whether it be dirt, suspended solids, or algae. One large adult oyster over three inches can filter up to fifty gallons of water per day.

You could deploy ten billion oysters in the Bay for restoration activities. With that amount of energy in the water, oysters can filter out a lot of suspended solids and clean the Bay.

When did scientists first see the decline of the oysters and have concern?

There’s actually an interesting book called The Oyster: A Popular Summary Of A Scientific Study (1891). It was written back in 1891 by William Keith Brooks, one of the oyster commissioners for the state of Maryland who was in charge of watching over the oyster population. It was a huge industry; people made millions of dollars off the oysters in the Chesapeake Bay. The commissioner saw the oyster depletion and wrote the book.

William Keith Brooks was a professor of zoology at John Hopkins University.   ©Wikimedia/Internet Archive
William Keith Brooks was a professor of zoology at Johns Hopkins University. ©Wikimedia/Internet Archive

Ken Paynter, a scientist through the University of Maryland, wrote the foreword on a reprint, which came out about a hundred years later. Brooks reflected that oysters are having problems and we could fix it now if we take certain steps, but it did not happen.

One of the ideas is relevant today in Virginia: using rotational reefs. If a healthy reef gets down to around ten oysters per square meter, they’ll close that reef from harvest and let it grow back. And maybe in three years they will open it back up again after a survey. That is what Brooks recommended. Back then in the 1800s, they had a lot more oyster larvae floating in the water column that could rehabilitate and reseed itself. If the watermen replaced the shells back in the water and the spat settled on it, harvest could happen in two years. You could then continue harvesting as long as you don’t overharvest.

He saw the writing on the wall. He wrote that book while he still was a commissioner and got fired.

To answer your question of when scientists first recognized the issue, I don’t even know. Somewhere in the 1800s, Connecticut area oystermen overharvested the oysters and basically didn’t have anything else to harvest.

The tool they had up in Connecticut was the dredge. They brought down the dredge to the Chesapeake Bay, and very quickly Maryland saw it was an efficient tool and made a law that prohibited dredging in the Chesapeake Bay unless you were a Maryland resident. So, Connecticut oystermen became Maryland residents.

Overharvesting oysters and oyster diseases in the 1950s changed some harvesting rules. Today, most large dredges are only used on skipjacks to harvest on public oyster bars.

What are some of the hurdles that have been encountered and overcome to restore oyster populations?

Challenges in oyster restoration include climate change, sea level rise, water quality, and oyster diseases.

There’s still poaching going on in certain areas of the Bay, which is a challenge for our DNR police. Other challenges include the cost of doing restoration correctly and the limitation on shell. Shell—that used to be free—is valuable now. People would give you bushels of shell when I first started restoration, but now it costs over $7 a bushel.

These bushels of oyster shells were used for oyster restoration efforts.  © U.S. Army Corps of Engineers Norfolk District/Wikimedia
These bushels of oyster shells were used for oyster restoration efforts. © U.S. Army Corps of Engineers Norfolk District/Wikimedia

Many watermen want to get involved in oyster aquaculture, but there is a cost to set spat-on-shell and put it in the water. That's another hurdle, the sheer cost and volume of work, but I see it getting easier in Maryland. The state has set aside an oyster aquaculture division within the Department of Natural Resources that helps the watermen/farmers.

DNR can make it quicker and less expensive to get involved in oyster aquaculture. The state needs to invite more watermen and other people switching over from wild oyster harvesting to oyster aquaculture, which is more sustainable.

We have very few wild oysters left in the Chesapeake Bay. Like old growth forests, some are in our oyster sanctuaries. These old reefs have tolerated diseases, water quality changes, and climate changes, and our new reefs can benefit from their offspring, creating more resilient reefs in the Bay.

It seems it’s quite a collaborative effort between the state, DNR, universities, and nonprofits.

Absolutely. We also have the public volunteering and voting, legislators creating new laws, and the watermen with extended knowledge. Watermen help in the restoration work. They’ll hire their boats out to pull up oysters and do monitoring plus seeding oysters back into the Bay.

There are multiple sectors in the oyster industry that are helpful. And they know they need to do the right thing to keep oysters in the Bay for generations to come.

Where does Maryland stand in relation to other oyster restoration efforts in the US and globally?

I’m pretty sure that the Chesapeake Bay is the leader of oyster restoration in the world. Other countries have been doing oyster aquaculture for hundreds of years, some being in Europe and Asia. Many efforts in oyster farming have been made, but restoration is a growing trend.

Being one of the largest restoration efforts in the world, it’s not done perfectly. It’s done the best we can and we learn, but, quite honestly, it has ended up going very well. Especially the first oyster sanctuary we finished at Harris Creek that met the fifty oysters per square meter mark. It is doing quite well and will be studied for years to come.

What are some of the target goals of the efforts here in Maryland and Virginia? I know you have ten tributaries, right?

Yes, that goal is ten tributaries, five in Maryland and five in Virginia by the year 2025, and we’re almost there. If you go out [in Virginia] and monitor their reefs over a season, more than likely they will get a natural spat set in those reefs. Just about every year or every other year, they’ll get one with a nice spat set, but it’s a little harder in Maryland. We’ve got to have the right salinity, so the upper reaches of the lower salinity areas may not a get a natural strike every year or a heavy set. It’s a little heavier lift up here to get a reef to sustain itself without the help of re-seeding it every couple years.

But at some point, the “tipping point” will be reached.

Finally, can an individual get involved in oyster gardening to help the restoration work?

Yes. If somebody wants to do it on a larger scale, we’ll work with them and give them the equipment they need. You can send an email to


*Gregg Jones is the outreach director of the Hyo Jeong International Foundation for the Unity of the Sciences (HJIFUS), the publisher of The Earth & I.


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