The Incredible Oyster
By Janelle Robbins,
Waterkeeper Alliance
Aphrodite, the Greek goddess of love, emerged from the sea on one. Roman emperors used to pay their weight in gold. Casanova started every meal by dining on 12 dozen of them. For millennia oysters have captivated the human imagination, satiated hunger and fanned the flames of desire. These marvelous mollusks also work tirelessly to filter and cleanse Earth’s precious water. But nearly a century of ecological abuse has put Mother Nature’s cleaners in hot water. Waterkeepers are now working to restore the oyster to its place of prominence.

History
By all accounts, North America was teeming with oysters in pristine bays and unadulterated estuaries when colonists arrived. The colonists were no strangers to oysters, but their ample size and bounty astonished them. Native Americans in coastal areas relied on oysters as a stable food source, building great jetties of oyster shells into the ocean after feasts. Initially, settlers collected oysters and other shellfish for personal consumption. At half the cost of beef, chicken or eggs at the time, oysters were a common and affordable fare. Settlers found many uses for the versatile oyster shells – they were crushed and used for paving roads and paths, as ballast in ships, as soil amendments to bolster depleted soil, burned for lime and as fill for wharves and lowlands. As new villages sprang up and old ones developed into cities, commercial harvesting of oysters boomed.

The westward expansion of railroads in the mid- and late-19th century created an all-out oyster industry explosion. Now, the tasty bivalves could travel by railcar, shucked and on ice, to be served up in speakeasies as far away as Chicago. There were soon oyster parlors, oyster cellars, oyster saloons, oyster bars, oyster houses, oyster lunchrooms and oyster stalls lining the streets of many American cities. In its heyday, the oyster industry supported 38,000 oystermen nationwide and 27 million bushels of oysters were harvested each year from 1880 to 1910. But by the end of the 20th century only around 4,000 oystermen were left, bringing in a meager 5.9 million bushels of oysters.

The Oyster Crash
The growing industrial economy exerted enormous environmental pressure on the oyster reefs of the Atlantic coast. The mining of oyster shells to make lime and for other uses depleted the amount of hard substrate for juvenile oysters to grow on, leaving the seafloor desolate instead of the dynamic undersea mountain range it once was. Sediment-choked runoff from developing cities smothered the oyster reefs, and those that were left were considered a navigational hazard and subjected to mechanical dredging, utterly destroying oyster habitat.

Along with declining oyster populations, the biggest blow to the oyster industry was poor sanitation. Raw sewage from early cities was piped, pumped and dumped, untreated, directly into coastal waters, contaminating oyster and other shellfish beds. While the sewage didn’t kill the oysters, the diseases that tainted oysters carried could infect and kill human consumers. Fouled oysters carried a plethora of human diseases, including cholera, vibrio and typhoid. The hysteria surrounding typhoid turned oysters from a gourmet delicacy to a scourge. Oyster saloons and bars were shuttered, oyster villages became veritable ghost towns and oystermen were left unemployed.

Oyster Ecology
Oysters grow in bays, estuaries, sounds and tidal creeks and rivers – anywhere from slightly salty to full seawater. In general, oysters are hardy creatures that can withstand relatively wide swings in temperature, salinity, suspended solids and dissolved oxygen.

Oysters are an integral part of a healthy marine ecosystem. Oyster reefs stabilize bottom sediments and create a habitat for other bottom-dwelling organisms, such as clams and aquatic vegetation. The reefs are home to barnacles, sea anemones and mussels. Nooks and niches in the reefs provide hiding spots for crabs and grass shrimp, and attract predators such as striped bass, bluefish and weakfish. Oyster reefs also serve as breakwaters, protecting adjacent shorelines from erosion.

But the oysters’ most ecologically important task is to filter and clarify water. Oysters are “filter feeders” – they suck water in, filter suspended particles out, and expel the clean water. An adult oyster can typically filter about 50 gallons of water a day. Over a century ago, the oyster population in the Chesapeake Bay could filter the entire bay volume, about 19 trillion gallons, in about six days. Today, it takes more than a year. Oysters filter out algae, improving clarity and putting the brakes on eutrophication – the filling in of a waterbody with sediment. Excess nutrients and phytoplankton are also strained out, as are suspended sediments from runoff and erosion.

Oyster Biology
Oysters are members of the phylum Mollusca, a group that also contains snails, squid, octopods and 100,000 other species. Oysters are bivalved, meaning they have two shells; an oyster’s shell is hinged on the narrow end, unlike a clam, which hinges on the wide end. The shell is approximately 80% of the oyster’s total weight and, since oysters don’t move, the shell is the only protection they have against predators. The mantle, a membrane-like organ, secretes nacre, which forms the inside of the shell. Under the mantle are the gills, which are used for respiration and moving water in and out of the oyster. Oysters also have a tentacle-like appendage called a foot. The foot is used for sensory reception and for cleaning the interior of the oyster shell. Oysters can tightly close their shell to avoid contact with an unhealthy environment, but the shell will open if the muscle tires, exposing the oyster to the dangerous outside world.

For an organism that is known as an aphrodisiac, oysters reproduce in a very unromantic manner. Males expel sperm into the water column while females release eggs. Only by a chance meeting does an egg become fertilized. About six hours after fertilization, the baby oyster is a soft free-swimming larva. Twelve to 24 hours later, the larva begins excreting a protective shell around itself. For the next three weeks the tiny oyster rides the currents, enjoying a brief period of motility. Finally, the oyster larva settles to the bottom, looking for a hard surface to attach to. The best substrate is an adult oyster shell, and oysters are gregarious – where one larva settles, others follow. This behavior creates reefs. After the larva settles and bonds to hard substrate, it is known as spat. The spat will metamorphose into an adult and live out the rest of its life on that spot. Oysters are ready to eat when they are about three years old.

Restoring Reefs
Replacing the oyster habitat destroyed in the early 1900’s requires new reefs where the baby oysters can attach and grow. This is done one of two ways: using manmade substrate or using shells. Reef balls are constructed from marine-friendly concrete with tiny niches where oyster spat will be out of reach from predators. Alternatively, clean oyster or clamshells can be dumped by the barge-load to create a new reef. Shell is often the most successful substrate, since juvenile oysters prefer to set on adult oyster shells rather than manmade materials.

Once you have a suitable reef habitat, you add oysters. During the summer, the oysters, which can be grown in floating cages called oyster gardens or in aquaculture facilities, are released onto oyster reefs.

Oyster research is an important part of restoration. Oyster diseases like MSX and Dermo kill oysters and hamper restoration efforts. Researchers are examining how the diseases are transmitted, how they can be stopped, and whether some native oysters carry a natural genetic resistance to them. In some locations, the use of MSX and Dermo resistant Asian oysters are being considered. But with so many non-native and invasive species clogging our waterbodies, the purposeful introduction of a non-native species is a highly volatile subject.

Waterkeepers at Work
Jay Charland, Assateague Coastkeeper, coastkeeper@actforbays.org
Assateague Coastkeeper (Berlin, Maryland) has oyster restoration efforts in St. Martin River and Chincoteague Bay. On the St. Martin River, Assateague Coastkeeper built a one acre oyster bed with 32 Taylor oyster floats and 80 additional bushels of oysters. A year later, a “spatfall,” or new generation of oysters, spawned and set on the shell substrate – a great affirmation of successful restoration efforts. Assateague Coastkeeper has a goal of creating ten acres of oyster beds in the St. Martin. A research oyster bed in Chincoteague Bay was seeded with one million spat bred to resist oyster diseases like MSX, Dermo and Seaside Oyster Disease. Oyster restoration can be risky business though – in a bout of over exuberance, the Assateague crew piled a pontoon boat high with oysters for transporting out to the Chincoteague Bay reef. Jay Charland realized en route to the reef that when he stepped to the edge of the craft it tilted perilously, threatening to capsize, so he jumped ship to save the oysters. Another time he found himself under attack while sampling the reef in St. Martin River from all fronts – jellyfish stinging his legs and vampire-like deer flies swarmed his face and arms.

Terry Backer, Long Island Soundkeeper, soundkeeper@aol.com
Long Island Soundkeeper (Norwalk, Connecticut) and their Yankee Oyster Project is busy protecting oyster aquaculture in Long Island Sound. The project seeks to limit the vulnerability of the Sound’s aquaculture fishery by identifying and promoting the growth of indigenous species of oysters that exhibit resistance to MSX and Dermo, and developing spawning, production and cultivation techniques that enhance oyster harvesting yields while reducing capital and operating costs.

Drew Koslow, South Riverkeeper, dkoslow@verizon.net
South Riverkeeper (Annapolis, Maryland) started oyster restoration projects six years ago by moving shell from a marine mining operation to a reef site by the bucket-load. The restoration efforts have gained speed and support, and South Riverkeeper now collaborates with the Maryland Department of Natural Resources, University of Maryland Horn Point Lab, Chesapeake Bay Foundation and Oyster Recovery Partnership to provide the best restoration they can. South Riverkeeper has built nine oyster reefs that vary in size from several hundred square feet to about one acre. Oyster garden projects provide South Riverkeeper with about 500 bushels of oysters a year for planting. In all, South Riverkeeper has planted about six million spat and approximately two million oysters have been grown by volunteers in 1,000 oyster gardens.

Katie McCrone, NY/NJ Baykeeper Oyster Program Technician, katie@nynjbaykeeper.org
New York/New Jersey Baykeeper (Keyport, New Jersey) is restoring oyster habitat in three locations – Liberty Flats by the Statue of Liberty, Keyport Harbor in Raritan Bay and Oyster Point on the Neversink River. New York/New Jersey Baykeeper oyster program staff have provided 1,350 New York and New Jersey residents with oyster education, and 730 volunteers have contributed 8,920 volunteer hours in planting 124,000 oysters and 88,000 spat, some of which were grown at 56 volunteer oyster gardening sites. Additionally, oyster program staff also monitor for MSX and Dermo.

David Bright, Mimosa Rocks Coastkeeper, ngairin@iprimus.com.au
Mimosa Rocks Coastkeeper (Tanja Lagoon, New South Wales, Australia) protects and advocates for the Wapengo and Nelson lagoons, which are prime Sydney Rock Oyster habitats – producing 10 percent of the continent’s rock oysters. The Mimosa Rocks Coast is located approximately 500 kilometers south of Sydney. The coastal lagoons produce award-winning oysters, but are threatened by siltation from logging operations of eucalyptus forests, as well as disease. Mimosa Rocks Coastkeeper has prevailed in a case to stop a wood-chipping operation until an ecological review, including impacts on oysters, is completed.