The Great Pacific Garbage Patch is a big problem largely because of all the tiny problems it contains. About 21,290 tons of microplastics are now sloshing around the eastern Pacific alone, according to a recent study, slowly crumbling under the region's harsh sunlight without ever truly breaking down.

Microplastics cause plenty of ecological damage around the world, but many also harbor their own weird ecosystems of opportunistic sea life. And as another new study indicates, some of those stowaways might be even more ecologically dangerous than the scraps of plastic they rode in on.

There's particular concern about Halofolliculina, a single-celled protozoan with wing-like tentacles that resemble devil horns. It plagues coral reefs by invading their limestone skeletons, causing a disease named skeletal eroding band (SEB) for a dark, coral-killing stripe that creeps across infected reefs. It also now surfs the open sea on crumbs of man-made trash, according to the new study, which investigates diverse "rafting communities" of tiny wildlife that cling to North Pacific microplastics.

"[We] found these little buggers living on plastic debris floating way offshore in the western Pacific, which wouldn't be terrifying in itself since a lot of strange critters live on plastic debris," lead author Miriam Goldstein writes in a post on Deep Sea News. "But Halofolliculina is a pathogen that causes skeletal eroding band disease in corals, and this piece of debris was headed toward Hawaii."


Rather than fully breaking down at sea, plastics often crumble into smaller and smaller pieces. (Photo: NOAA Marine Debris Program)

First discovered in 1988 near Papua New Guinea, SEB once seemed limited to parts of the South Pacific and Indian oceans — until it was found in the Caribbean in 2004 and Hawaii in 2010. The new study may be too late to keep Halofolliculina out of Hawaii, but it could still shed light on how these diminutive devils got there. And with reefs around the world already immersed in man-made dangers, any insight that might thwart future invasions could mean life or death for entire marine ecosystems.

"The mechanism behind the spread of SEB are not known," the study's authors write, "but since the Hawaiian Islands are highly impacted by plastic debris collected by the North Pacific subtropical convergence zone, it is possible that debris facilitated the dispersal of Halofolliculina to this area."

It's unclear whether plastics were Halofolliculina's only ticket to Hawaii, Goldstein points out, but they apparently could have been. And based on the biodiversity found on such minuscule pieces of seafaring plastic, it is clear that garbage patches are becoming much more than just garbage.

"Along with Halofolliculina, there are all kinds of creatures living on plastic debris that wouldn't normally be able to survive floating in the middle of the ocean," Goldstein writes, citing regular rafters like gooseneck barnacles, bryozoans and rafting crabs along with less expected interlopers such as brittle stars, sea spiders and a shipworm. "Essentially, the trash acts like tiny little islands."

With so many of those islands now adrift in the Pacific — not to mention other oceans and even lakes — their full environmental impact won't be easy to assess. But given the known dangers of plastic pollution, plus the possibility of invasive hitchhikers, it's unlikely the planet's growing masses of marine plastic will turn out to be paper tigers. And while cleaning up these messes is all but impossible, the study's authors suggest the best way to weaken a garbage patch is to simply stop feeding it.

"[A]ny potential impacts of the debris-associated rafting community on coastal or pelagic ecosystems can be most effectively limited by an overall reduction in the quantity of plastic pollution introduced into the marine environment," they conclude. Or, as Goldstein adds in layman's terms, "plastic does not belong in the ocean, and we have really got to stop putting it there."

Russell McLendon is science editor at MNN. Follow him on Twitter and Google+.

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