Dissecting the Cause of Death in the Gulf - Oceana USA
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July 15, 2010

Dissecting the Cause of Death in the Gulf

Warning: what follows isn’t exactly light reading.

The New York Times reported yesterday on the complicated task of performing necropsies — i.e., animal autopsies — on sea turtles and other creatures that have been found dead in the Gulf of Mexico since the spill started.

It’s not easy to determine the cause of death of these creatures. Of the 1,978 birds, 463 turtles and 59 marine mammals found dead in the Gulf since April 20th, few show visible signs of oil contamination.

And in the case of sea turtles, a more familiar culprit may be at fault: shrimp trawls and other commercial fishing gear that scoop up turtles as bycatch and prevent them from going to the surface to breathe.

Here’s a simplified breakdown of how the veterinary investigators begin to determine the cause of death:

1. Death by BP crude oil:

If they find oil residue on an animal, investigators will use chromatographic spectrum analysis to determine if it has the same “chemical signature” as BP crude.

2. Death by dispersants:

If an animal is found hemorrhaging, dispersants could be the cause. Dispersants contain solvents that can break down red blood cells, causing hemorrhaging. At least one dolphin found dead in the Gulf was bleeding from the mouth and blowhole.

3. Death by fishing gear:

If a creature has sediment in its airways or lungs, it’s good evidence of drowning in fishing gear. In addition, if a Kemp’s ridley sea turtle has recently ingested shrimp, that’s a good indication it was caught in a shrimp trawl. Kemp’s ridleys are normally not fast enough to catch shrimp.

And this list doesn’t include the indirect causes of death — such as boat strikes as a result of the possible “narcotic effect” of oil that may render some creatures unable to get away fast enough.

Investigators plan to take tissue and fluid samples of the creatures to test them for disease and hydrocarbons, as well as for dispersants, but believe it or not, the NYT reports that no samples have yet been sent to labs, because NOAA scientists are still debating what types of results will prove most useful.

Oceana’s campaign director Jackie Savitz told the Times that there was no excuse for the delay.

“It’s absolutely urgent that it should be done immediately.”

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