The impacts of the growing oil spill in the Gulf of Mexico has still not fully become evident, but the potential implications to the region known for its abundant and diverse fish and wildlife could be devastating, reports the Wildlife Management Institute. Direct damage or mortality caused by contamination from oil and the chemical dispersants being applied to break up the spill are the most immediate concerns. However, the longer-term impacts to the coastal habitat of the Gulf Coast states could be felt for decades if a substantial amount of oil makes its way into the? region's already fragile wetlands.

Efforts to contain the oil slick and skim and remove the surface oil are continuing and will play a large part in determining exactly where and how bad the impacts are to the region. Although some oil has started to wash up onshore at the Breton and Bon Secour National Wildlife Refuges as well as other parts of the Louisiana coast, containment efforts thus far have kept most of the oil slick offshore. According to the U.S. Fish and Wildlife Service, 25 national wildlife refuges could potentially be impacted.

The spill was caused by the explosion and collapse of the Deepwater Horizon offshore oil rig on April 20. The well is more than 5,000 feet below the surface, making the efforts to cap the well and stop the leak much more challenging. The National Oceanic and Atmospheric Administration (NOAA) estimates that the well is leaking 210,000 gallons (5,000 barrels) of oil into the Gulf daily. At that rate, it is estimated that 4 to 5 million gallons of oil are in the Gulf's waters already. However revelations by lease-holder, BP, during a congressional briefing on May 11 suggest the rate of the leak could be much higher, perhaps as much as 60,000 barrels each day. Either way, it is very likely that this spill will surpass the 1989 Exxon Valdez spill of nearly 11 million gallons that is still the worst oil spill in U.S. history.

The most immediate danger is to seabirds, fish, marine mammals and sea turtles. Direct mortality or injury from oil spills can occur when oil coats bird feathers reducing their buoyancy, and when birds groom themselves ingesting the oil and causing damage to internal organs. So far there has been about a dozen bird rescues, primarily brown pelicans and northern gannets, from the Deepwater Horizon spill. Officials also have expressed concerns about oiled wildlife damaging eggs during this primary nesting period. Marine mammals and turtles also may come into direct contact with the oil as they rise to the surface. The deaths of six dolphins and dozens of sea turtles have not been conclusively linked to this spill, but state wildlife officials said that the brunt of the direct impacts is yet to be seen.

The indirect effects of the oil spill as it stays offshore are associated primarily with impacts to fish spawning and contamination of food sources. The oil slick on the surface of the water will block sunlight, damage fish eggs and impact plankton that is a primary food source for numerous fish and wildlife species. In addition, concerns have been raised about the toxicity and effectiveness of the chemical dispersants being used to break up the oil, causing it to settle on the ocean floor. More than 430,000 gallons of the dispersant Corexit?a product described by its manufacturer as similar to household soaps and detergents?have been dropped on the oil slick , yet little research has been done on how the proprietary chemical ingredients will affect the ecosystem. The chemicals are likely to kill fish larvae, shrimp, coral and other marine life. The dispersed oil that settles on the ocean floor also is likely to smother ocean plants and persist in the environment, remaining highly toxic for decades as it slowly degrades. Little is known how ocean currents will affect subsurface movement of the contaminants when it can no longer be tracked. Currently, the decision to use the dispersants is a tradeoff to protect the region's fragile wetlands at the potential expense of its marine life.

The greatest potential long-term impacts from the oil spill are if and when the oil reaches the coastline. About 40 percent of the nation's coastal wetlands are found along southern Louisiana and even before this oil spill there has been a dramatic decline?estimated at 20,000 acres lost each year?in these wetlands. About 4.7 million ducks, including lesser scaup, canvasback, redhead, teal, pintail and wigeon, winter offshore in the coastal marshes of southeastern Louisiana. Had the spill occurred in the winter, it would have been devastating to waterfowl, but most wintering ducks have moved out and the greatest risk at present is to resident mottled ducks that currently are brood rearing. The marshes also provide the breeding habitat for numerous shellfish species such as shrimp, blue crab and oysters, as well as speckled trout, redfish and other fish species?about 20 percent of the nation's commercial seafood originates in coastal Louisiana. Should the oil reach the marshes in a thick, tar-like consistency it will smother the vegetation there, which could lead to erosion and subsidence of the marshes, adding to the wetland loss happening before this crisis.

Already, the collapse of the Deepwater Horizon and the resulting oil spill are impacting the region's economy. A vast area of the Gulf has been closed to commercial fishing and the persistence of contamination in fish and shellfish could close the fishery for an extended period of time. In addition, the potential affect on tourism for these coastal areas is substantial. However, it will not be clear what the impacts to the region's natural systems is for some time. (jas)