(14-06-10) Giant plumes of crude oil mixed with methane are sweeping the ocean depths with devastating consequences. Now, we can see a disaster on the surface, but we must be also worried about the great underwater disaster, the effects on marine life that we cannot see yet.

    It was in mid-May that scientists detected the vast underwater plumes of crude oil spreading like medusa’s locks from the out-of-control gusher in the Gulf of Mexico. BP immediately dismissed the reports, also Federal officials called the scientists’ claim “misleading, premature and, in some cases, inaccurate.

    Now it is increasingly clear that the initial reports of undersea oil were right, that life-giving oxygen in the water column is indeed being depleted, and that unless the laws of chemistry have been repealed, dispersants are likely worsening the tentacles of undersea crude. What might have been just another oil spill—albeit a bad one—has been transformed into something unprecedented.

    The Deepwater Horizon disaster will enter the record books not for how much but for where: an enormous release of crude oil not only onto vulnerable shorelines and fragile marshes but into the largely unexplored depths of the sea.

    The consequences for the delicate balance of existence in the vulnerable ecosystems of the gulf, and for the vast cycles of nature that sustain life there and beyond, are as incalculable as they are potentially devastating.

    We must worry about oil on the surface. It’s going to cause very substantial and Now noticeable damage—marsh loss and coastal erosion and impact on fisheries, dead birds, dead turtles—but we’ll know what that is. It’s the things we don’t see that must worry the most. What happens if you wipe out all those jellyfish down there? We don’t know what their role is in the environment. But Mother Nature put them there for a reason,” and many are in the plumes’ paths.

AN UGLY ALCHEMY AT 5,000 FEET DOWN

    Their presence has blown to smithereens the cliché that oil floats on water. That correctly describes what happens when pure crude spills into the sea from a well in shallow water or a tanker at the surface, as happened with the Exxon Valdez. But when a gusher is 5,000 feet down, consists of a mix of crude oil and dissolved methane, and is being disgorged under tremendous pressure and temperature, studies predict that the physical and chemical properties of the spill will undergo an ugly alchemy.

    The dispersants are changing the chemistry and physics of the oil, they are creating microlayers of oil that are being carried by the deep currents. Even without dispersants, the crude gets broken into zillions of droplets suspended in the water column and corralled there, prevented from rising to the surface. The result is the undersea plumes first detected from the research vessel Pelican three weeks after the blowout.

    Making matters more worst, the chemical dispersants that work fairly well on surface spills, breaking apart oil slicks into droplets that degrade more quickly than a contiguous layer, may be exacerbating the undersea-oil problem.

    A 2007 report by the Minerals Management Service—which OK’s oil and gas leases—on the environmental consequences of oil and gas drilling on the outer continental shelf concluded that an underwater plume is a real possibility.The use of dispersants on oil spills could cause these compounds to reach the deeper water reef areas.

    BP has pumped 185,000 gallons of dispersant onto the out-of-control wellhead (plus 800,000 on the surface). That is causing more of the gushing crude to break up into the very form unlikely to rise to the surface. There have been no suggestions that BP intended to keep the worst of the spill out of sight.

    As far as scientists can tell, the undersea oil is actually a witch’s brew of crude mixed with dissolved methane, stretching 15 miles long, 5 miles wide, and 300 feet thick in the case of one plume detected by the Pelican, and 22 miles long, 6 miles wide, and 3,000 feet thick in the case of a plume found by University of South Florida researchers aboard the WeatherBird II last week. The latter plume reaches all the way to the surface.

ONLY DETECTED BY SOPHISTICATED INSTRUMENTS

    NOAA’s skepticism about plumes is correct on one point. Contrary to what the phrase conjures up, oil plumes are not black serpentines. The USF researchers caught one on camera last week, but in general they can be detected only by sophisticated instruments lowered into the depths. Samples hauled up do not even look black, though when they are run through a filter, black specks are revealed.

    These undersea rivers of oil, though not nearly as concentrated as oil at the surface, are likely to affect the gulf through two mechanisms: The first is oxygen depletion, which has been estimated at 30 percent in the plumes. The other will be direct toxic effects of the oil and methane.

    Leatherback turtles and sperm whales dive to the 3,200-foot depths where plumes have now been detected, and aren’t smart enough to take evasive action. They don’t necessarily recognize the plumes as something dangerous. Sharks, shrimp, and squid are all inhabitants of the deep, which would protect them from a Valdez-type spill on the surface, but now puts them in the crosshairs.

    Marlin, snapper, and grouper swim hundreds of feet down. One of the biggest losses may be bluefin tuna. Already imperiled from overfishing, the species breeds only in the Mediterranean Sea and the gulf. This could spell the end to bluefin tuna. Even small bits of crude, like those in the plumes, can suffocate fish by gunking up their gills.

    Other species imperiled by the deep-sea plumes include those that migrate down from the surface and others that make the reverse commute. There are plankton that go from the surface to the middle of the water column, and other things eat them and go down deeper, and other things eat them and go to the bottom. All the zones of life interact, and now they’re probably all being hammered.

    The worst effect of large-scale death on the gulf floor is nothing as photogenic as dead pelicans, but much more pernicious. The organisms most likely to be harmed by the oil plumes are those at the base of the food chain. Most of the primary producers, such as phytoplankton, live throughout the water column. Effects on them would cascade to the larger species we care about.

    Uniquely in the crosshairs are creatures living at or near the sea floor: deep-sea corals, jellyfish, and soft-bottom fish such as Atlantic croaker, sand seatrout, Atlantic bumper, sea robin, and sand perch. Three coral reefs live in the area under the surface slick, and two are close to one plume that scientists tracked last week. Oil could be lethal to a reef.

    Of special concern are the hundreds of “seep” communities in the gulf, enclaves of crustaceans, weird tube worms, tiny fish, mussels, and crabs that live near natural gashes in the sea floor. These seeps release hydrocarbons, which might suggest that the oil-and-methane plumes are good for these creatures.

    Oil on the ocean surface eventually evaporates, is degraded by sunlight, gets consumed by microbes, or washes up on beaches, where it can be collected. The fate and effects of the undersea oil are largely unknown.

Text: Guadalupe Romero