Crafty coastal species are colonising plastics – with potentially devastating results

The sheer volume of plastics dumped, trickled or escaped into our oceans is seen as a major global problem, threatening biodiversity, injuring or killing vulnerable marine animals, and even harming human health.

Now, new research shows life can bloom even in the direst of places: coastal plants and animals are actually colonising floating plastic debris in the open ocean.

The study, published in Nature Communications, describes findings of coastal flora and fauna thriving afloat on plastic garbage hundreds of kilometres out to sea in the North Pacific Subtropical Gyre, more commonly known as the ‘Great Pacific Garbage Patch’. It proves once again – in case we needed reminding – that nature is a crafty and adaptable beast.

But the discovery doesn’t write off the wrongs of plastic pollution, nor does it bode well for marine ecosystems.

“The issues of plastic go beyond just ingestion and entanglement,” says Linsey Haram, lead author of the article and a former postdoctoral fellow at the Smithsonian Environmental Research Center (SERC), US.

“It’s creating opportunities for coastal species’ biogeography to greatly expand beyond what we previously thought was possible.”

That means potential new frontiers for creatures that have always lived in geographically contained zones.

“The open ocean has not been habitable for coastal organisms until now,” says SERC senior scientist Greg Ruiz, who heads the Marine Invasions Lab where Haram worked on this new research. “Partly because of habitat limitation – there wasn’t plastic there in the past – and partly, we thought, because it was a food desert.”

In order to establish whether the theorised colonisation of floating plastic debris was really happening at scale, Haram teamed up with Ocean Voyages Institute, a non-profit that collects plastic pollution, and oceanographers Jan Hafner and Nikolai Maximenko from the University of Hawai’i at Manoa.

Hafner and Maximenko created models that could predict where plastic was most likely to pile up in the Pacific Garbage Patch, which flows on established systems of currents.

Woman sorting floating plastic debris on a boat
Anika Albrecht of Ocean Voyages Institute, on a 2020 expedition collecting floating plastic debris in the North Pacific Subtropical Gyre, where she served as Chief Mate. Credit: Ocean Voyages Institute 2020 Gyre Expedition

The Institute collected 103 tonnes of plastics and debris from the patch in a single year, some of which was sent to SERC’s Marine Invasions Lab. There, Haram analysed the species that had colonised the floating plastic debris, and found an astonishing range of species living and thriving there, including anemones, hydroids and amphipods.

It’s yet another example of humans creating paradigm shifts in natural ecosystems, and Ruiz says scientists are still not sure exactly how these plastic-bound creatures are getting their nutrients – but it could be that the plastic itself acts like a reef, and attracts more food sources.

It means marine scientists now have an entirely new food system to contend with, and one that’s highly mobile and could feasibly drift into all sorts of geographical zones.

“Coastal species are directly competing with these oceanic rafters,” Haram says. “They’re competing for space. They’re competing for resources. And those interactions are very poorly understood.”

It also raises the threat of biological invasion. This kind of invasive colonisation has already played out when large bodies of water shift, for example when the 2011 Japanese tsunami carried debris – and accompanying organisms – from Japan to the coast of North America.

But vast colonies of marine species floating in the ocean for years at a time could expand the opportunities for invasive species to cause havoc in delicate coastal communities.

“Those other coastlines are not just urban centres…That opportunity extends to more remote areas, protected areas, Hawaiian Islands, national parks, marine protected areas,” Ruiz says.

While the authors don’t yet know how common these hitch-hiking communities are, the global dependence on plastics shows no sign of abating. Cumulative plastic waste is estimated to soar to 25 billion metric tonnes by 2050. Coupled with the fact that climate change is stirring up increasingly frequent and violent coastal storms – as we’re seeing on the east coast of Australia – that pollution will continue to be thrust out to sea.

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