BP-oil threatens cold-water corals

Photo by: Igor GOLUBENKOV

Thousands of barrels of oil continue to leak into the ocean from British Petroleum’s Deepwater Horizon each day, and as we have been able to see in countless news reports a lot of it reaches the surface.

Less well known is that a significant portion of the oil never make the full 1 502 meter (4928 feet) journey to the surface. Instead, the stratified waters of the Gulf of Mexico capture the oil or slow down its ascent, and this oil is now threatening numerous life forms far below the surface.

According to Dr Gregor Eberli, Dr Mark Grasmueck and Ph.D. candidate Thiago Correa – all three from the Marine Geology & Geophysics division of the University of Miami (UM), the oil that fails to reach the surface is a serious threat to planktonic and benthic life throughout the region, including many species of cold water coral. Planktonic life is all the tiny living creatures the drift around in the ocean, while benthic life is life confined to the sea floor.

“The deep water communities within the Gulf of Mexico and in the Straits of Florida are well hidden from us, but they include many species of cold-water corals that live in water at depths of 600 — 1500 m. (1969 -4921 ft.) in waters as cold as 3° Celsius (37.4°F),” Eberli explained.  “Unlike their more familiar shallow-water counterparts, these corals do not live in symbiosis with unicellular algae called zooxanthellae, but are animals that feed on organic matter floating through the water column. We know that most of the food consumed by the cold-water corals is produced in the surface waters and eventually sinks down to the corals.”

To make the problem even worse, the large plumes formed as a result of the oil spill has placed themselves between the deep-water corals and their food source. Some of these plumes are several miles long, and organic material – i.e. animals and plants – that sink through the plumes will become contaminated by micron-sized oil droplets. These droplets might not look as dramatic as a sea surface filled with crude oil, but they are equally damaging.

“It is most likely that the delicate cold-water corals are not able to digest these oil-laden food particles and will perish in large numbers,” said Eberli. “We are especially concerned because the migrating oil plumes have the potential to destroy or greatly diminish these deep-sea coral communities as they are carried by the currents. These corals are important because they are the foundation of a diverse ecosystem that at last count includes over 1,300 marine species, according to Dr. Thomas Hourigan at NOAA.”

Severe damages might not be limited to the Gulf of Mexico

The Loop Current transports water from the Gulf of Mexico to the Atlantic Ocean, passing through numerous significant coral sites on its way from the eastern Gulf of Mexico through the Straits of Florida and northward to the Blake Plateau off North Carolina. The water enters the Straits of Florida to form the Florida Current and further north the Gulf Stream. Tiny droplets of oil suspended in the water could therefore wreck havoc with ecosystems far away from British Petroleum’s Deepwater Horizon.

While several (albeit not perfect) methods do exist for cleaning crude oil from the surface of the ocean, we know hardly anything about how to rid the water column from oil plumes.