The area around the BO rig hosts 1,728 species, among them whale sharks, tarpon, tuna, sea turtles and sperm whales.

“The greatest part of the Gulf ecosystem is out of sight beneath the surface,” says Larry McKinney, executive director of the HRI. This largely unmonitored region, he adds, is “incredibly sensitive to the toxic effects of oil and dispersant”, as well as to the low oxygen levels associated with deep-water plumes.

Nature investigates five of the Gulf of Mexico’s signature species

by Melissa Gaskill

http://www.nature.com/news/2010/100630/full/466014a.html

Species: TARPON  (Megalops atlanticus)

Risk: Ingestion of oiled prey diverts metabolic energy from the fish’s other needs. Oil and dispersants can coat gills and primitive lungs (which are used to breathe at the surface).

Species: BLUE FIN TUNA Bluefin (Thunnus thynnus)

Risk: Oil causes larvae deformation and death.

The northern Gulf of Mexico is a crucial breeding ground for the Atlantic bluefin tuna, one of the world’s most important commercial fish.

Even if tuna eggs escape unscathed, the hatched larvae face a loss of food supply. Oil reduces primary production of phytoplankton and zooplankton, on which larval fish depend for food, says Shirley, which implies that few tuna larvae are likely to survive in the oiled sections of the Gulf this year.

Species: KEMP’S RIDLEY SEA TURTLE (Lepidochelys kempii)

Risk: External exposure to oil causes burns and infections. Ingestion or inhalation damages digestive and respiratory systems, liver, kidney and brain; causes immune suppression, reproductive failure and death.

 Females are known to enter the spill area post-nesting. Juveniles and adults forage there. More than 425 dead sea turtles have been reported in the spill zone and conservationists fear that more have been killed where oil was ignited to control its spread.

Species: WHALE SHARK  (Rhincodon typus)

Risk: Direct contact with oil could fatally coat gills. Oil could reduce or contaminate plankton, the whale shark’s primary food source.

The world’s largest fish, whale sharks are filter feeders that subsist on fish spawn and plankton blooms — foods typically available off the Mississippi River delta in the summer.

Species: SPERM WHALE (Physeter macrocephalus)

Risk: Inhaling volatile components can lead to unconsciousness, pneumonia, organ damage and death. Direct contact with oil and dispersants causes skin and eye infections. Oil in prey accumulates in tissue, causing disease and a decreased reproductive rate.

About 1,700 vulnerable sperm whales live year-round in the Gulf, rarely straying from essential habitat within 100 kilometres of the Mississippi River delta — the area of the spill. The animals breathe at the surface and dive deep to feed on squid, exposing the whales to oil and dispersants at a range of depths.