Monday, June 21, 2010

Sharks and Submerged Oil Spell Trouble Off the Alabama Coast

A two-inch layer of oil is hugging the sea floor off the Alabama coast, according to a report in the Mobile Press-Register. The news comes roughly a week after a layer of floating crude came ashore in the same area at the Bon Secour National Wildlife Refuge.

Perhaps most alarming is news that unusually large schools of sharks have been spotted just off Alabama beaches. This could be a sign that bait fish upon which sharks feed have moved closer to shore because of low oxygen levels caused by the BP oil spill.

The Press-Register report provides more grim evidence of the oil spill's impact. Writes reporter Ben Raines:

The Press-Register found a number of patches of submerged oil 40 to 100 feet off the beach, apparently collecting along rip currents and sandbars. The carcasses of sand fleas, speckled crabs, ghost crabs and leopard crabs were spread throughout the oil, a thick layer of the material caking the bodies of the larger crabs. Their claws looked as if they been turned into clubs made of oil.

Those weren't the only alarming scenes from Raines' report:

Dark patches seen in deeper water Friday might also have been oil, but exceptional numbers of large sharks meant diving down to investigate was not an option. Hammerhead, bull and other sharks were schooling around a boat anchored in 6 feet of water just outside the breaking waves.

Most of the sharks in the deeper water were 6 feet long or more. Smaller sharks could be seen inside the first sandbar, in one case in a school 27 strong.

Huge schools of bait hugged the seashore, attracting large numbers of birds. King mackerel, Spanish mackerel, mullet, ladyfish, speckled trout and other fish schooled in unusually large numbers amid the sharks.

Dead fish seen onshore seemed to have collected in the areas closest to the underwater oil. It was unclear if the fish died because of exposure to the oil.

Scientists are reporting very low oxygen levels off the Alabama coast, Raines reported:

The Dauphin Island Sea Lab measured large areas of low oxygen water just off the beach at Fort Morgan last week, beginning in water around 20 feet deep. Monty Graham, a University of South Alabama scientist, theorized that the population of oil-consuming microbes had swelled, and those tiny animals consumed lots of oxygen.

Sea life begins to die if oxygen levels drop below 2 parts per million.

Graham found some areas where the oxygen level was below 1, and that could explain reports of strange behavior among fish:

"The low oxygen explains things we've been hearing, like reports of flounder swimming on the surface," Graham said.

The low oxygen levels offshore may also explain the dense aggregations of fish seen in the surf zone. The turbulent area near shore is naturally high in oxygen due to the influence of the breaking waves.

You can check out a video report from the Press-Register about current conditions on the Alabama coast.

Submerged oil at Bon Secour shoreline


Anonymous said...

But, of course!

Anonymous said...

have heard the same thing about schooling fish from Pensacola to the Keys...