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Oysters once flourished in the Chesapeake Bay, providing habitat for aquatic life and supporting a thriving oyster fishery. But disease, water pollution and decades of over-harvesting have drastically reduced their numbers. One restoration project is getting area residents involved in oyster recovery efforts.
Volunteers get involved in Maryland program
On a warm, sunny morning in late August, volunteers gathered at a marina on Maryland's Severn River, one of the tributaries of the Chesapeake Bay on the mid-Atlantic coast of the United States. They were there to kick-off the second year of a project called Marylanders Grow Oysters. Chris Judy directs the program for the Maryland Department of Natural Resources.
"What's going to happen is, a truck will arrive with cages loaded with oyster spat [which are] young oysters. The cages will be loaded on boats and trucks and distributed to the volunteer oyster growers we have," Judy explains.
The volunteers are not marine life professionals. They are local residents who live along the rivers that flow into the Chesapeake Bay. Each will take care of several cages filled with about 80 oyster shells. Attached to each shell are some 10 baby oysters, called spat. Each one measures less than one millimeter in diameter.
In nature, just a few oyster larvae would survive
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The spat come from the University of Maryland's Horn Point Laboratory. Don Meritt runs the lab's oyster hatchery restoration program. He explains that the oyster life cycle is fairly complex. "Oysters in the winter have no developed gonad at all, in fact you can't even tell a male from a female," Meritt says.
As the water temperature warms up in the spring, the oysters start to produce eggs and sperm. In the summer, once the water gets warm enough, they release those eggs and sperm out into the water column where fertilization occurs. At the hatchery, Meritt and his staff can manipulate water temperature to control the oysters' reproductive cycle.
A single female will typically release 10-30 million eggs, during a half hour spawning event. The fertilized eggs hatch into oyster larvae; each smaller than a grain of sand. Meritt says that in nature, almost none of those survive.
Hatchery improves the odds for oyster survival
At the hatchery, a sophisticated computerized system delivers four species of algae to hungry oyster larvae in eight tanks of water, each holding close to 38,000 liters. In a lab near the larval tanks, Don Meritt takes a small plastic container out of a refrigerator and unwraps what looks like a blob of brown muck. He says we are looking at 5.4 million oyster larvae.
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Meritt smears a bit of the muck on a slide and puts it under a microscope. Magnified through the lens, the muck transforms into dozens of tiny, translucent pairs of shells.
In the water, the oyster larvae propel themselves around with tiny hair-like structures called cilia. After a few weeks, the ones that have survived start to settle to the bottom.
"At that point they look like a little snail," says Meritt. The larvae crawl around looking for a piece of hard clean substrate that suits them. "Once they find that," Meritt describes, "then they actually cement themselves to that substrate." At that point, the larvae lose the ability to move themselves around. "So if you're an oyster you get one shot to pick the place you're going to live the rest of your life, and you better be smart at it," Meritt says.
Oyster larvae settle down and get attached
In the Chesapeake Bay, oyster larvae try to improve their chance of survival by attaching themselves to other oysters.
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At the hatchery, the larvae settle down as spat in large outdoor tanks, each holding eight stainless steel mesh cages filled with 96,000 oyster shells. Last year, the hatchery produced over 550 million spat, for a wide range of oyster restoration sites. Some were intended for harvest and some for protected sanctuaries, like those supported by the Marylanders Grow Oysters program.
Oysters find new homes with volunteer caretakers
This is Tom McCollum's first year as a volunteer. "It's just a great way to teach my kids as well as make a difference," he says.
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The McCollum family will be caring for three oyster cages in the water off their pier. The program plans to distribute a total of 5,000 to area residents.
After about nine months, the Maryland Department of Natural Resources will collect the oysters and transfer them to a sanctuary in the Severn River. As adults, they will provide many environmental benefits including filtering algae and sediment out of the water and creating habitats for crabs, fish, and other aquatic life.
Although Meritt says the number of oysters these volunteers raise will be relatively small compared to overall Chesapeake Bay restoration efforts, he stresses that the biggest benefits of the program are educational. "The environmental awareness is huge. And that's where the real effect of this is. It demonstrates to the property owners and their kids and their grandkids and their neighbors, everybody around, just how unique oysters are and what kind of a wonderful animal this is, and how the Chesapeake Bay is going to be so much better off for everybody if we can get enough oysters back out there to start doing the job that they used to do."
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Video: [Video credit: University of Maryland Center for Environmental Science Horn Point Laboratory (UMCES/HPL) Oyster Hatchery Program] |