Gulf oil disaster still puzzles scientists

One year after the chocolaty crude started spewing out of the bottom of the Gulf of Mexico, leading to the largest accidental oil spill in history, scientists say they're still trying to piece together what's happening to the environment.

Some potential clues about the impact of the spill have made themselves known: dead baby dolphins and sea turtles; oiled brown pelicans; fish with strange sores; sticky marsh grasses; tar balls on beaches.

But the big picture hasn't come into focus yet.

Did the oil spill shatter the Gulf's food chain? Will fish have trouble reproducing because of exposure to hydrocarbons? What did those dispersants, which were supposed to break up the oil, do to the ecosystem on the bottom of the Gulf of Mexico? Or did the Earth already heal itself?

Scientists can't say for sure, and it may be years or decades before some of these nagging questions about the Gulf oil disaster's impact will be answered with any sort of authority or clarity, they said in interviews....