Dispersion spares surface-dwelling animals, such as birds and otters. But as oil drifts downward, it falls on fish and on the eggs that are stuck to surfaces or buried in the sediment. To find out just how dangerous dispersed oil might be to fish, Hodson and colleagues performed a series of laboratory experiments with beakers that were meant to simulate contaminated lakes. In all of the beakers, the scientists mixed water with diesel oil, then added newly hatched trout embryos. In some beakers, the scientists added a dispersing agent. Their analyses, published in the journal Environmental Toxicology and Chemistry, showed that dispersants greatly increased the amount of hydrocarbons that could affect fish. In turn, that extra dose of exposure made the oil 100 times more toxic to the animals. Toxicity was measured as an elevated enzyme response in the livers of the fish. Exposure to dispersed oil doesn't kill a lot of fish, Hodson added. Instead, it either kills eggs before they hatch or leads to damage or deformities in juvenile fish. Compared to the horrifying appearance of oil-drenched birds on beaches, it can be hard to catch the attention of the public -- or even of cleanup managers -- with such subtle and hidden health effects. "What he's saying, and he's correct, is that it could be way more fish fingerlings or eggs that are impacted than you'd ever impact birds," Kinner said. "It kind of adds fuel to the discussion." Another message of the study, Kinner added, is that, when it comes to accidents that involve oil, there are no easy answers and no happy endings. "Once the petroleum product is spilled, there is going to be damage no matter what," she said. "It's already a bad situation. The question is: How are we going to minimize the risks as much as possible?" Related Links: Go to Discovery Earth for slide shows, quizzes, interviews and more. |
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