Ike’s Hidden Damage
TPWD leads efforts to restore oyster reefs and salt marshes after the 2008 hurricane.
By Lance Robinson
Hurricane Ike, the costliest hurricane in Texas history, made landfall across the east end of Galveston Island on Sept. 13, 2008. A storm surge of 15 to 20 feet above normal tide levels was reported along the Bolivar Peninsula and part of the Galveston Bay area. In Chambers County, to the north of Galveston, the tidal surge reached more than 11 miles inland.
The aftermath of Hurricane Ike was very visible to those living in the area and, through extensive media coverage, to the rest of the country as well. As devastating as the damage was to homes and businesses in the coastal communities of the upper Texas coast, less visible but significant damage also occurred to coastal habitats in the region and below the waters of Galveston Bay.
Emergent saltwater and brackish water marshes along the upper Texas coast were heavily eroded or inundated with high-salinity waters from the Gulf of Mexico. The Salt Bayou Marsh, the largest emergent marsh system in Texas, lost more than 700 acres. Erosion of the dune ridge along the beach adjacent to the McFaddin National Wildlife Refuge in Jefferson County exposed 45,000 acres of brackish water marsh to an influx of salt water.
As the high tidal surge and waves moved across the Bolivar Peninsula, thousands of cubic yards of sand and debris were swept into East Galveston Bay. Much of this material settled onto oyster reefs in Galveston Bay, smothering the reefs with up to a foot or more of sediment and burying the hard substrate necessary for oyster larvae to attach and grow.
The Texas Parks and Wildlife Department began mapping submerged habitat in 2007 (as a result of impacts from Hurricane Rita in 2005) using sidescan sonar technology. Comparing bottom habitat maps made before Hurricane Ike to those made after the storm revealed losses of more than half the oyster habitat in Galveston Bay. East Galveston Bay, between Smith Point and the Bolivar Peninsula (where the strongest quadrant of the storm made landfall), had oyster habitat losses of at least 80 percent. TPWD estimates that more than 6,000 acres of oyster habitat were lost in Galveston Bay as a direct result of Hurricane Ike. The estimated cost to restore this habitat to pre-hurricane condition is $300 million.
Through a special appropriation by Congress, a $7 million fishery disaster grant was made available to Texas in 2009 from the National Oceanographic Atmospheric Administration (NOAA). These funds were earmarked for oyster and marsh habitat restoration in the affected area.
Hurricanes are natural events that have been occurring for thousands of years, and similar losses to habitat have occurred in other areas of the Gulf, so the question arises: Why restore these features? The answer: Salt marshes and oyster reefs are two of the most productive and valuable ecosystems found along the Texas coast. The benefits that we receive from these ecosystems are priceless.
TPWD employees and volunteers on the upper Texas coast have been planting grasses to restore marsh areas, such as at Galveston Island State Park. Similar work to restore Ike-damaged marshes has taken place at J.D. Murphree Wildlife Management Area and McFaddin National Wildlife Refuge.
Marshes provide many valuable ecological services to coastal ecosystems and have been described as one of the most biologically productive habitats on Earth, often compared to tropical rainforests. Marshes function as biological filters by slowing runoff and allowing contaminants to settle, so excess nutrients are absorbed and utilized for plant growth. As plants die, the accumulation of decaying plant material provides critical nutrients for a variety of small invertebrates at the bottom of the food web. In turn, these tiny creatures are consumed by juvenile shrimp, crabs and fish.
Functioning as a nursery, marsh edges also provide refuge for these feeders. In fact, the majority of the inshore commercially and recreationally important species — shrimp, blue crabs, flounder, red drum and spotted seatrout — spend a portion of their life cycle in these habitats. Salt marshes help reduce coastal erosion by dissipating wave energy and serving as sediment traps. The effects of coastal flooding can be minimized by marshes, which slow runoff and absorb rainwater.
The upper Texas coast is dominated by marshes that range from freshwater marsh to intertidal salt marsh (covered at high tide, uncovered at low tide). A portion of the Salt Bayou Marsh system is located at the J.D. Murphree Wildlife Management Area, where marsh loss is at a rate approaching 1 percent per year. Hurricane Ike changed upwards of 700 acres of the system from vegetated marsh to shallow open water from scouring due to the storm surge.
Most people know oysters as an ingredient in gumbo, as the namesake in Oysters Rockefeller or simply in raw splendor on the half-shell, but oysters are so much more than a delicious source of food.
Marine biologists often refer to oysters as “ecosystem engineers” or “foundation species.” An ecosystem engineer is a species that creates or modifies habitat, while a foundation species is one that has a strong role in structuring a community. Oysters, by attaching and growing upon cultch (any substrate upon which juvenile oysters cement themselves) and other oysters, create reefs. These reefs are habitat for numerous other reef organisms. The reef community is structured around the oysters.
The importance of this reef-building ecosystem service cannot be underestimated, as it is linked to nearly all other oyster ecosystem services. For example, oysters improve recreational fishing. Large, predatory fish like to gather around three-dimensional structures, and there’s an abundance of small prey species for larger fish to feed on within crevices in the reef structure.
Oyster reefs also function as natural bio-filters. A single adult oyster can filter about 50 gallons of water in one day, removing small, suspended particles from the water and improving water quality and clarity.
Consider the scale of this operation. A 130-acre oyster reef with 10 adult oysters per square meter will filter approximately 260 million gallons of water in a day. By comparison, it takes 39 wastewater treatment plants in Houston to filter a comparable amount.
In addition to improving water quality and clarity, the filtering activities of oysters also have a positive effect on the aquatic food web. The tiny particles removed from the water by oysters include many microscopic plants and animals (collectively known as plankton). Oysters are selective about which filtered particles they actually ingest, and they reject much of the plankton that they capture as something called “pseudofeces.” Since these psuedofeces contain many undigested planktonic organisms, they are a valuable food source for many small worms, crustaceans, fish and other reef-dwelling organisms.
Oyster reefs can serve to stabilize shorelines and reduce erosion when they occur parallel to shore as fringing reefs. Fringing reefs can intercept incoming waves and greatly reduce their energy, minimizing erosion and damage.
And yes, in addition to these ecological services, oysters are a popular and valuable seafood item. The Texas oyster fleet harvests about 5.8 million pounds of oysters annually, valued at about $17 million. The commercial oyster industry provides significant economic benefit to coastal communities and certainly contributes to the wonderful quality of life on the Texas coast.
Marsh habitat restoration
By using sediments dredged from the nearby Golden Pass Liquefied Natural Gas ship terminal, the shallow open water and subsiding marsh areas at Salt Bayou were raised to an elevation conducive to healthy marsh growth. Thanks to the partnership with Golden Pass, funds intended to restore about 40 acres of marsh were leveraged to restore about 1,600 acres of intertidal marsh within the Salt Bayou Marsh system, over 40 times the original goal. The areas were also planted with marsh species, such as smooth cordgrass and saltmeadow cordgrass, to accelerate revegetation.
Disaster grant funding is also being used to protect more than 45,000 acres of marsh within the Salt Bayou system by replacing a four-mile section of the beach ridge at McFaddin National Wildlife Refuge. This beach ridge suffered erosion from Hurricane Ike and now receives overwash during high tide events, allowing sea water into the Salt Bayou marshes. The berm construction will protect the coastal marsh system from the high salinities of the Gulf.
Once completed, these projects will result in the enhancement, protection and restoration of approximately 54,000 acres of coastal marsh.
Oyster reefs create homes for many organisms. Work is under way in Galveston Bay to restore reefs.
Oyster habitat restoration
Since September 2009, more than 1,300 acres of oyster habitat have been restored in Galveston Bay. These oyster restoration projects were ranked based on the thickness of sediment overlaying the reef. More than 174,000 tons of cultch — materials such as oyster shell, river rock or crushed concrete — have been placed onto 200 acres of sediment-covered reefs. For areas where sediment depths were less than three inches, more than 160 commercial oyster fishermen were contracted to pull dredges to bring buried shell to the surface, re-exposing the hard substrate. This oyster habitat will become available for harvest in a couple of years.
In East Galveston Bay, where the largest loss of oyster reef occurred, the Texas Parks and Wildlife Department closed the area to all oyster harvest for two years, allowing the surviving oysters to spawn. Coupled with the department’s oyster restoration projects in the area, the newly settled oysters were able to establish, grow and spawn over two seasons before being harvested. Where there were no oysters growing after Hurricane Ike, by the fall of 2011 the restored reefs were home to more than 356,000 oysters per acre.
Though the unsightly scars from Hurricane Ike are fading, the less visible natural resource recovery in the area has been slower. With optimum growing conditions, these coastal habitats would take decades to return to their former state. Unfortunately, conditions are far less than desirable. Reduction in freshwater inflows, loss of sediment inputs in the upper reaches of estuaries from rivers and ongoing drought conditions all combine to slow this natural recovery along the upper coast.
Ongoing restoration efforts along the Texas coast by TPWD and others are mitigating many of these obstacles and accelerating the return of these hidden yet important natural resource victims of Hurricane Ike.