Corps efforts offer new hope for oysters, environment
February 9, 2011
- The oyster population in the Chesapeake is estimated to be less than one percent of its size during the 19th century.
- The filtration process is significant to the water and aquatic life - it consumes algae, clarifies the water, helps bay grasses thrive
- Creating larger oyster populations for water purification increases fishery stocks for watermen
- Oysters on the restored reefs in the Great Wicomico are measuring up to six-inches and longer after six years of reef growth.
- Chesapeake Bay Foundation
- Oysters disappearing worldwide: study
- Virginia Institute of Marine Science
- City of Virginia Beach
- USACE NEWS
- HQ USACE
- Virginia Marine Resources Commission
- Lynnhaven River Now
- Norfolk District, USACE
- Chesapeake Bay Program - A Watershed Partnership
- Oyster Restoration - NOAA, Chesapeake Bay Office
The native American oyster - diseased, overfished and languishing in dismal water - couldn't ask for a better friend than David Schulte.
During the hot and humid summer months when sun bathers line the white sandy beaches and stroll along the Virginia Beach boardwalk, built by the U.S. Army Corps of Engineers more than 20 years ago, Schulte douses himself with sunscreen, puts on his trademark straw hat, white cotton tank shirt and shorts, and spends the day going from oyster sanctuary to oyster sanctuary, measuring the size of oysters and gathering underwater imagery of the reefs built since 2004. In the winter, as swirling winds and temperatures dip to 30-degrees, the Midland, Pa. native is bundled up and on the water checking the reefs and thinking of innovative ways to naturally enhance the population of oysters.
Schulte, a marine biologist at the Norfolk District, U.S. Army Corps of Engineers, is turning a barren portion of the Great Wicomico and Lynnhaven Rivers into blossoming oyster reefs, teeming with healthy oysters.
But the shuck doesn't stop there: he has set his sights on the Painkatank River and its potential to become the next Wicomico.
The oyster population in the Chesapeake is estimated to be less than one percent of its size during the 19th century, according to the Maryland Department of Natural Resources. Over time, overfishing, pollution, destruction of habitat and, most recently, disease ravaged the oyster population.
Oysters are a key species for the bay's health because they act as a filter, improving water quality. Chesapeake's historic oyster population could filter the Bay's volume every three or four days. Today's oyster population would take more than a year to filter the same amount of water, according to the Maryland Department of Natural Resources.
The filtration process is significant to the water and aquatic life - it consumes algae, clarifies the water, helps bay grasses thrive and reduces shoreline loss. Fish and crabs hide in the small crevices and holes created by the oysters and shells that make up the reef.
The Norfolk District became involved with native oyster restoration in 1999. The first two projects, in the lower Rappahannock River and the Tangier Sound, were designed to help the commercial oyster fishery. The project's mediocre success required the Corps to go back to the drawing board. The Corps' new strategy became geared toward ecological restoration: developing self-sustaining oyster populations on restored reefs.
With that in mind, Schulte and the U.S. Army Corps Lynnhaven Oyster Restoration Project Team set out restore the reefs and built them to mimic the historical high reef structure from the 1800's, Schulte said.
The vertical design worked, Schulte said. Previous reef construction required a thin shell layer a few inches thick on the bottom. The new blueprint called for a minimum reef height of 12 inches, simulating historic oyster reefs. The goal was to populate tributaries leading to the Chesapeake Bay with protected reefs. The hope then was for a process called recruitment.
During recruitment, oyster adults spawn on the reefs and release tiny larvae into the water. The larvae drift in the water for up to three weeks, looking for a new home. With the primitive eye and foot they develop near the end of their larval phase, they're looking for prime real estate: a hard object, preferably another oyster, to settle on.
"Once they 'set' the baby oyster loses its foot and eye, never to move again, transforming into a tiny version of what we see on our plates when we order oysters on the half-shell," Schulte said.
Creating larger oyster populations for water purification increases fishery stocks for watermen, which means more revenue for the approximately 1,800 full-time watermen left standing after the bay's decline.
Ken Smith, president of the Virginia Waterman's Association, said deterioration of the Chesapeake Bay's health took its toll on watermen. About 5,000 watermen used to work the bay, but when the tides changed, they were forced to find other work, said Smith.
"It was good living when I started, and in the mid 80's, that changed," he said. "I make half of what I used to bring home and the decline is a direct reflection of the health of the Chesapeake Bay ... We stopped having fish in those areas; they were dead zones."
The Corps partnered with the VMRC and Virginia Institute of Marine Science to revive the fading oyster population and increase recruitment in Chesapeake Bay tributaries, and constructed the first Wicomico River reefs in 2004. Starting with the Wicomico reef habitat, Schulte and his team decided to focus on a tributary-by-tributary fashion, starting with small, tidally retentive systems most likely to provide oyster recruits for restored reef habitat. One of the goals of the Great Wicomico River oyster restoration project was to increase local recruitment, and thus, the population.
In just a few years, the team's efforts paid off. The adult oyster population on remnant habitats - former reef bases that were dormant and covered with silt and algae - were now home to baby oysters from protected reefs, and the oyster population had increased from 630,000 to 13.80 million by 2008. The adult oyster population on the restored habitat was 119.20 million in 2007 and was about the same in 2008 - in 2004, there was not a single mollusk on the habitat.
Schulte said the team was successful, and the Virginia Marine Resources Commission moved some of the Great Wicomico recruits, or "seed" oysters, to areas for later harvest, while leaving the sanctuaries alone to produce still more recruits in the future.
"The restored reefs are now performing better than we could have hoped," Schulte said. "The tides have changed - both for watermen and the recruitment of oysters."
Smith, the 40-year waterman who has worked the northern neck of the Wicomico, Potomac and Rappahannock Rivers and tributaries, believed that if the bay was clean, nature would take care of the rest. For Smith, seeing is believing.
"Now there is grass growing there that we haven't seen in years ..." Smith said about Glee Point at the northern neck of the Wicomico. "Oysters are piling up on the rip-rap, pilings, rocks along the shoreline - I attribute it to the recruitment from the Corps' reefs."
During a recent trip to the Lynnhaven, Schulte measured oysters six- to eight-inches long on protected reefs. The average oyster ranges from three- to-four inches. Oysters on the restored reefs in the Great Wicomico are measuring up to six-inches and longer after six years of reef growth, Schulte said. Disease killed some of the oysters, but many survived and new baby oysters, called "spat," have recruited to the reefs in large numbers. This should allow the reefs to continue to be a home for many millions of oysters, Schulte said.
"That's amazing and it shows us that it is only going to get better," he said.
The Corps protects thousands of oysters with aquaculture netting, which is part of an anti-predator experiment. These oysters and larger shell reefs built in 2007 and 2008 are thriving at several sites in the river. Early monitoring is showing some of the restored reefs are on a track similar to the older Great Wicomico high-relief reefs.
The findings from Wicomico, which have been published recently in the journal Science, indicate that the restoration project resulted in a 57-fold increase in the Great Wicomico oyster population and is currently the largest restored oyster reef network in the world. Adult oyster densities are averaging about 700 per square meter of reef, with about 300 young oysters, called "spat," adding up to about 1,000 oysters per square meter of high relief reefs. These densities have never before recorded in the modern-day Chesapeake Bay. The oysters are all from wild recruitment, not planted "spat-on-shell."
"This is the first time the Chesapeake Bay Program goal of a 10-fold increase in native oysters has been met in any location, and we exceeded it by almost six times," said Col. Andy Backus, commander of the Norfolk District, U.S. Army Corps of Engineers, which manages the project for the federal government.
"I have seen first-hand the positive ecological impact this project has had. We hope to increase the existing Lynnhaven River from fifty to sixty acres of reefs to one hundred acres and do additional plantings of spat-on-shell baby oysters on some of the restored reefs," Backus said.
The Corps, Lynnhaven River Now and the City of Virginia Beach, with the endorsement of the Commonwealth of Virginia, were instrumental in overlooking and continuing the efforts once the U.S. Army Corps Lynnhaven Oyster Restoration Project started, Schulte said.
Schulte and the U.S. Army Corps Lynnhaven Oyster Restoration Project Team received the Coastal America Partnership Award in 2009 for their innovative and successful ongoing efforts to restore and protect the coastal environment, specifically, the Native American Oyster, in the Lynnhaven River.
But this doesn't mean Schulte will spend a lot of time sitting idle - he can usually be found on the waters of the Great Wicomico, Lynnhaven and canvassing the Painkatank River as a potential site as research and solutions continue.
Did you know'
The Chesapeake Bay watershed is approximately 64,000 square miles. The Lynnhaven basin is about 64 square miles and in many ways is a microcosm of the Chesapeake Bay. The watershed is heavily urbanized, and much of the original forested areas and a sizeable portion of the wetlands, which once lined the river, is now lost. In the 1890's, James Baylor, who surveyed all of Virginia's oyster grounds, called Baylor Grounds, delineated 986 acres of public oyster grounds in the Lynnhaven River, specifically in Broad Bay, Linkhorn Bay, Crystal Lake and Lynnhaven Bay.
By the mid-1970s the natural oyster reefs in the Lynnhaven River were essentially gone except for a few scattered patches, less than one acre in size.
All of the Lynnhaven River's waters were closed to shellfish harvest of any sort due to high bacteria levels in the water. However, the Corps considered the river a good candidate site based on several factors: the history of high oyster recruitment in the river, its once-extensive oyster beds and the high-density remnant oyster population where the Corps found more than 1,000 oysters per square meter of stone rip-rap along shorelines. The Corps estimated there were 10 million to 20 million oysters, scattered mostly on rip-rap and along marsh edges throughout the Lynnhaven River system, prior to the proposed Corps reefs. Some of the adults were observed at 5 to 7 inches in length, which indicated the wild Lynnhaven oyster had significant resistance to the diseases MSX and Dermo. Both diseases typically kill native oysters when they are 1 to 2.5 inches in length.
The Corps first proposed the Lynnhaven River as a potential restoration site in 2003 and planning began in 2004. Several small reefs were built in the river prior to the planning, but due to their design and placement, had not done well. By consulting with physical oceanographers and using a hydrodynamic model, the Corps determined that the design of the prior reefs caused them to trap excessive amounts of sediment and their locations were not ideal for receiving or providing oyster larvae.
The Corps used the hydrodynamic model to help place the Corps-built reefs in better locations. The Corps also found and used historic information about Baylor Grounds in the Lynnhaven River. The information was lost for many years after the Commonwealth of Virginia removed all Baylor, or public, oyster grounds managed by the state and surrendered them to private industry.
The reefs were built in two stages during 2007 and 2008. The City of Virginia Beach provided funding for spat on shell: a hatchery bred wild Lynnhaven strain oysters, "set" the resulting larvae on shells in the hatchery and then planted on several Corps-built reefs identified as being "source reefs." These reefs, once mature oysters are on them, will provide oyster larvae to most areas throughout the Lynnhaven River system. This spat on shell amounted to more than 5,000 bushels of baby oysters, numbering more than 10 million planted oysters on the corps "source" reefs.
Currently, 60 million to 90 million oysters live on Corps reefs. Many of these survived disease and grew to a large size, especially the City of Virginia Beach spat on shell, some of which are up to 6 inches long now. The Corps plans to construct more reefs and plant more spat on shell, increasing oyster recruitment throughout the river. The Corps is in the process of building about 40 more acres of reefs over the next few years and hopes to exceed 200 million oysters in the Lynnhaven River.