But.... what's to keep the sea turtles from swimming under the berms and into the sea???
It might be the nature of the berm itself - size, depth it goes to, etc. But I believe it's due to these other reasons:
Turtles breath air - though they have an extremely high lung capacity and dive-depth like Penguins and Whales.
In the water which is riddled with oil (oil isn't just on the surface) the oxygen content is dropping *in* the water itself which means (confirmed) oxygen level depletion.
This means that air-breathing animals have to come to the surface more often to breath.
Once on the surface they get thoroughly coated with oil.
This might hinder their ability to swim (can swim as fast) and can't dive as deep (lack of use of flippers, etc)
As well as oil and chemical toxicity - I imagine it's not safe and sound - they're likely suffering from effects of intoxication, not just oil-coated flippers and oxygen levels being depleted - but intoxication in their bloodstream due to content of the water/oil/chemical dispersants.
Therefor the surface seems, to a turtle, to be the smartest idea - the thought of diving deep to possibly leave the area simply might be out of their capacity - especially if the oil surrounds them in a large area.
Let's say a turtle is on the oily surface - realizes it's a bad place to be - and then dives to try to get away - comes up 40 feet away - in more oil. Then dives again - comes up in more oil.
How far, how deep does an animal have to swim to get away from it? At what point will that animal become too exhausted/sick to continue?
Birds that fly are also getting caught up in this tragedy - why can't they just fly away? Same thing - physical changes. Oil is thick, sticky and gooey - like a really thick syrup.
Animals aren't exposed to enough oil-spills to adapt. They can avoid other various natural disasters (fire, earthquake, etc) to a more successful degree because they happen frequently enough to adapt to those conditions and respond in the best way to avoid tragedy. but oil-spills don't happen often enough for a species to adapt and then pass that adaptation down to the offspring - which is why oil spills are so tragic.