Oil spill imperils an unseen world at the bottom of the gulf
Sunday, May 16, 2010
In total darkness at the bottom of the Gulf of Mexico lives a creature with many scuttling legs and two wiggling antennae that jut from a pinched, space-alien face. It is the isopod, Bathynomus giganteus, a scavenger of dead and rotten flesh on the mud floor of the gulf.
"If you think of a giant roach, put it on steroids," said Thomas Shirley, a marine biologist at Texas A&M University. "They can be scary big."
There is beauty in the lightless deep as well. Fan corals, lacylike doilies, form gardens on the seafloor and on sunken ships. The deep is full of crabs, sponges, sea anemones. Sharks hunt in the dark depths, as do sperm whales that feed on giant squid. The sperm whales have formed a year-round colony near the mouth of the Mississippi River, and have been known to rub themselves on oil pipes just like grizzlies rubbing against pine trees.
This is the unseen world imperiled by the uncapped oil well a mile below the surface of the gulf. The millions of gallons of crude, and the introduction of chemicals to disperse it, have thrown this underwater ecosystem into chaos, and scientists have no answer to the question of how this unintended and uncontrolled experiment in marine biology and chemistry will ultimately play out.
The leaking gulf well, drilled by the now-sunken rig Deepwater Horizon, has cast a light on a part of the planet usually out of sight, out of mind, below the horizon, and beyond our ken. The well is surrounded by a complex ecosystem that only in recent years has been explored by scientists. Between the uncapped well and the surface is a mile of water that riots with life, and now contains a vast cloud of oil, gas and chemical dispersants and long, dense columns of clotted crude.
"Everybody fixates on the picture of the cormorant or the bird flailing around all covered with oil, and while that's obviously sad to see, no one should assume there's not similar things occurring in the open ocean," said Andy Bowen, an oceanographer at Woods Hole Oceanographic Institution in Massachusetts. "It's not like the open ocean is irrelevant."
More is known about the surface of the moon than about the world at the bottom of the sea. Scientists long ago clung to the "azoic hypothesis" about the deep -- the presumption that nothing could possibly be alive so far from the photosynthetic world.
Gradually that belief succumbed to living proof to the contrary. Life finds a way. Instead of photosynthesis, there is chemosynthesis. Organic matter rains into the depths from higher in the water column. Oil itself is a part of this mysterious universe, leaking naturally from the seafloor. It is testament to life's ingenuity that for some bacteria, oil is food.
The broken well is 5,000 feet below the surface, on the continental slope, which is the long hill that runs from the edge of the continental shelf to the abyssal plain in the central gulf. The pressure is about 2,230 pounds per square inch, 152 times that of the atmosphere at sea level. The temperature is just a few degrees above freezing.
But the Deepwater Horizon well is in an area that is comparatively well explored. Scientists have been actively studying the deep coral reefs of the gulf, in many cases venturing personally in submersible vessels that can withstand the crushing depths. This strange realm can be disorienting.
"It's sort of like being in the Grand Canyon with the lights out and in a snowstorm," Bowen said.
The topography is full of knolls, hills, canyons -- the leaking well is located in Mississippi Canyon Block 252 -- and the sea bottom is not simply mud.