Gulf Oil Spill Effects on Underwater Life

Chemical Dispersants

• As part of the clean up, BP used 1.8 million gallons of chemical dispersant to break sheets of oil into drops that sink below the surface. The dispersant kept the oil from coating beaches and shoreline, but also made it easier for animals to ingest the drops as they moved through water, and to consume drops of oil stuck to plankton. University of West Florida biologist Wade Jeffrey believes oil may have entered the lowest levels of the food chain and may "cascade up" to larger organisms. Scientists suspect oil and dispersant have triggered new diseases in fish and have played a role in the high number of baby dolphins that have washed ashore dead in 2011.

Fish

• Crude oil clogs fish gills compromising the respiratory systems, while toxins from hydrocarbons take a toll on reproductive and immune systems. Fishermen have caught red snapper with black skin lesions and rotting fins, while female snappers have been found with deformed ovaries. Roughly 20 percent of the bluefin tuna died in the spill, a significant loss for the species that has declined significantly over the past 20 years. Conservation groups fear sturgeon and sawfish, two endangered species, may be at greater risk of extinction because of the oil.

Coral Reefs and Other Habitats

• Scientists surveyed the ocean floor near the spill site and discovered severe damage to coral reefs. Penn State University biologist Charles Fisher found a black substance coated roughly 90 percent of the coral, which was either dead or dying. Coral reefs are critical habitats that support roughly 25 percent of all marine life. Seaweed and marsh grasses, important habitats for many underwater species, also show signs of stress that may be due to millions of gallons of oil that have sunk to the ocean floor and seeped into the sediment.

Invertebrates

• Oysters, shrimp, crabs, sea stars, sea cucumbers and other invertebrates have been hit hard by BP oil. Large areas of oyster beds were destroyed during the spill. Shrimp boats report meager catches, and some shrimpers are pulling up tar balls in their nets. Researchers have found traces of oil in blue crab larvae, a species often used as a benchmark of the health of an ecosystem. Marine biologists are monitoring the direct effects of the oil on these species and the effects of species who feed on these species.