PHOTO: The living shoreline of cordgrass and oyster reef was built by NOAA to protect Pivers Island in Beaumont, North Carolina. NOAA Fisheries
Oysters and other shellfish are highly popular menu items, particularly in coastal towns where fresh seafood is readily available. These seaside communities are also the very places most likely to suffer flooding — and now an ingenious plan has been concocted to utilize the mountains of used shells generated by the eateries. There is now a plan to use the shells to reduce flooding!
Scientists have long known that oyster beds can help anchor vulnerable coastline and prevent erosion. However valuable these beds may be as far as environmental protection, they have not been adequately protected from overfishing and other depredations. In addition to the threat from over-harvesting, large swaths of oyster populations have been severely damaged by the increasingly intense storms that have decimated the coastline in recent decades; even established oyster reefs can be damaged if the storm is fierce enough. Acidification of the oceans due to man-made pollution also takes a toll. And lastly, oyster populations have been scraped off the sea floor by dredging and pier construction projects.
Now, thanks to recently developed techniques, there are plans in place around the country to rebuild the huge oyster communities of yesteryear, using discarded oyster shells to help get the new shellfish started. The new plans use the natural habits of the oysters to benefit both shellfish and humans! Oysters typically cement themselves to a fixed, hard object as part of their survival strategy. Lacking means of locomotion, they must affix themselves to a permanent location that offers good water circulation. Oysters are filter feeders and are believed to filter up to 50 gallons of water per day. Plankton, decomposing plant and animal material, and other organic particles are filtered by the oysters and utilized to glean nutrients. Oysters are extremely efficient as filters of other undesirable compounds and matter as well, such as nitrogen and algae, and are able to greatly improve the health and clarity of the water bodies that host them. This is yet another beneficial side product of the flood-busting scheme.
As the oysters cement themselves to the sea floor or other underwater features, their irregular shells provide habitat for many other aquatic creatures. Over time, with good husbandry and ideal conditions, huge reefs of oysters can build up, and these reefs can act as natural sea walls. The obvious advantage of these living flood barriers is that they are built and maintained by the natural organisms themselves! Once the oyster reefs are “planted” in the desirable location, the oyster reef is built over time by the oysters, and is always getting bigger and stronger with no further expenditure of dollars or human labor.
So attractive is this relatively cheap and extremely effective natural flood barrier, that federal grants have recently become available to initiate “artificial” oyster reefs in strategic locations from Manhattan to Louisiana. Enter the contributions from the seafood industry: here is where those mountains of used shells are put to good use. Oyster fry must find shelter in order to survive, and the corrugated shape of natural oyster shells are the best bet for them to find protection while they mature. So now, instead of discarding huge mounds of shells into landfills, an after-market has been created to make use of the shells in the most environmentally positive way. The used oyster shells are placed in the correct locations to form natural sea walls, and fry are introduced. Soon the dead shells provide the right conditions for new living reefs to form, and the mature oysters begin to clean the water even as they help protect from floods. A true win-win scenario!