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Passage:
A new paper published by Rochman and her colleagues in February, in the journal Ecology, sifts through past research on marine debris to assess the true extent of the environmental threat. Plenty of studies have sounded alarm bells about the state of marine debris: Rochman and her colleagues set out to determine how many of those perceived risks are real Often. Rochman says, scientists will wrap up a paper by speculating about the broader impacts of what they've found. Maybe their study has shown that certain seabirds eat plastic bags, for example, and the paper goes on to warn that whole bird populations are at risk of dying out. "But the truth was that nobody had yet tested those perceived threats." Rochman says. "There wasn't a lot of information." Rochman and her colleagues examined more than a hundred papers on the impacts of marine debris that were published through 2013. Within each paper. they asked what threats scientists had studied-366 perceived threats in all and what they'd actually found. In 83 percent of cases, the perceived dangers of ocean trash were proven true. In most of the remaining cases. the working group found the studies too shoddy to draw conclusions from—they lacked a control group, for example. or used faulty statistics.
Strikingly. Rochman says, only one well-designed study failed to find the effect it was looking for, an investigation of mussels ingesting microscopic plastic bits. The plastic moved from the mussels' stomachs to their bloodstreams. scientists found. and stayed there for weeks—but didn't seem to stress out the shellfish. A lot of ocean debris is "microplastic," or pieces smaller than five millimetres. These may be the beads from a facial scrub. fibres shed by synthetic clothing in the wash. or eroded remnants of larger debris. Compared to the number of studies investigating large-scale debris. Roclunan's group found little research on the effects of these tiny bits. There are also, she adds, a lot of open questions about the ways that ocean debris can lead to sea-creature death. Many studies have looked at how plastic affects an individual animal or that animal's tissues or cells, rather than whole populations. And in the lab, scientists often use higher concentrations of plastic than what's really in the ocean. None of that tells us how many birds or fish or sea turtles could die form plastic pollution or how deaths in one species could affect that animal's predators, or the rest of the ecosystem. "We need to be asking more ecologically relevant questions." Rothman says. Usually, scientists don't know how disasters like oil spills or nuclear meltdowns will affect the environment until after they've happened. she says. "We don't ask the right questions early enough." But if ecologists can understand how the slow-moving disaster of ocean garbage is affecting ecosystems. they might be able to prevent things from getting worse.