Crude oil is edible for bacteria, but it’s not exactly something you’d want to see on the dinner menu. Recent research suggests oil can enter the food chain, which means residues could make their way into our seafood.

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Researchers at Alabama’s Dauphin Island Sea Lab found oil’s fingerprints on the coastal ecosystem.

In the months after BP’s Deepwater Horizon oil spill, bacteria in the Gulf of Mexico feasted upon the carbon-rich oil. Those bacteria then became food for other microorganisms, called zooplankton. The zooplankton in turn became food for fish, jellyfish, and whales.

The scientists looked for certain types of carbon in the zooplankton to trace the carbon’s origin. Oil tends to have more of the lighter form of carbon, called carbon-12. Other food sources have more of the heavier carbon-13.

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Zooplankton from the area affected by BP’s Deepwater Horizon spill contained enough carbon-12 to suggest that oil had entered their food chain.

William Graham, who headed the study, said scientists knew bacteria would eat the oil, but were unsure how much oil residue would enter the rest of the food web.

Graham and his colleagues can’t say for certain if this means oil toxins have entered the food chain. But it does show a pathway exists from the oil spill to the food chain.

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Further studies are looking at how the oil changed productivity in the ecosystem, and exactly how quickly it happened.

If oil residues are building up in the food chain, they will be more concentrated in the creatures at the top. Humans sit at the top of the food chain in the Gulf, so Graham’s research could give us clues about the safety of Gulf seafood.

The Dauphin Island Sea Lab’s research was published in IOP Publishing’s Environmental Research Letters.