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Plastics, those indestructible relics of our throwaway culture, are omnipresent in the oceans, making their way into everything from sea salt to seabirds. Now, a new study finds seabirds may be giving back, shuttling particles from ocean garbage gyres back to shore in their poop. Around colonies where seabirds congregate, the pungent white streaks may form halos of plastic pollution—contaminating soil and potentially cycling back into the sea.
The study, conducted on northern fulmars in the frigid waters off Canada’s Labrador Peninsula, is the first to measure plastics in seabird guano. The idea arose when a group of researchers studying plastic ingestion by seabirds were having coffee and pondering where the junk they found stuffing birds’ stomachs might ultimately wind up.
“We thought, let’s take a look in there and see what we find at the end of their gastrointestinal tract,” says Jennifer Provencher, a marine ecologist at Acadia University in Wolfville, Nova Scotia, and lead author on the paper.
Local Inuit hunters collected 30 of the stocky gull-like seabirds, which nest by the tens of thousands in the rocky cliffs of Baffin Island, Nunavut. The researchers dissected the birds’ stomachs and intestinal tracts. What they found was eye-opening.
“Almost all of the birds had plastics in their stomachs,” Provencher says. “Half had microplastics in their poop.” Most of the plastics were dust-sized fibers—and most were blue, although some were black or red. Provencher is trying to figure out what the various colors mean. The excreted fragments are likely a mix of remnants of larger pieces that had been ground up during digestion and microfibers that are now ubiquitous in the environment.
The new study shows marine animals have a role in transporting plastics throughout the ecosystem, says University of Toronto ecologist Chelsea Rochman, who studies contaminants in aquatic ecosystems but was not involved in the new research.
“What I think is interesting is that some of these birds forage quite far out to sea and now they’re coming onto land and shuttling that plastic around,” says Rochman. “Should we be surprised that it’s in their poop? Probably not. Should we be thinking about it? Probably.”
Provencher suspects that vast numbers of plastic-eating birds pooping in the same place could create halos of plastic pollution around the colonies. Previous research has shown that seabirds transport chemical pollutants such as DDT and PCBs from the ocean to land. Not only could microplastics add to the pollution burden, but endocrine-disrupting phthalates and other harmful chemicals used to manufacture plastics could leach out. On top of that, plastics are themselves magnets for waterborne pollutants.
An estimated 4.4 to 12.7 million tonnes of plastics enter the oceans annually, where more than 100 species of seabirds have been found to ingest them, either directly or in plastic-contaminated prey.
“The more plastics the birds have in their stomach, the more they poop out,” Provencher says. “That means that for birds that are colonial, that hang out by the tens of thousands, there is a potential for that poop to make a difference” to the wider ecosystem.
Scientists don’t yet know how the excreted plastics may affect soil and marine ecosystems. “We’re just on the cusp of figuring out what is going on with guano and plastics,” says study coauthor Mark Mallory, also at Acadia University. In a worst-case scenario, Mallory says, plastic runoff could enter the ocean food web and be eaten by larger predators, further concentrating the pollution. The researchers will be investigating the potential ecosystem effects of plastics around fulmar colonies in northern Canada later this summer.