Oceanic gyres are vortexes of water which occur where multiple ocean currents meet, linking into a system of circular ocean currents. The largest of them is North Pacific Subtropical Gyre (NPSG) and you’ve likely heard of the infamous Great Pacific Garbage Patch that exists within it.
Large amounts of floating human-made debris are transported and concentrated there, but according to a new study in PLOS Biology, so is floating marine life.
“The ‘garbage patch’ is more than just a garbage patch. It is an ecosystem, not because of the plastic, but in spite of it,” says Dr Rebecca Helm, a marine biologist at Georgetown University in the US and senior author of the paper.
Known as obligate neuston, marine surface-dwelling organisms play a critical role in the ocean surface food web. They include sea life such as jellyfish, snails, barnacles, crustaceans, and algae –which are thought to be transported and concentrated by ocean surface currents.
But scientists know very little about where these organisms live, and until now only one oceanic region has been known to concentrate them: the Sargasso Sea in the Subtropical North Atlantic gyre.
But researchers have identified another thanks to citizen science.
In 2019, long-distance swimmer Benoît Lecomte undertook an 80-day, almost 278-kilometer swim from Hawaii to San Francisco in the US. His marathon journey took him through the NPSG and the researchers asked the sailing crew accompanying him to collect daily samples of sea creatures and plastic waste.
His route was planned using computer simulations of ocean surface currents to predict areas with high concentrations of marine debris.
“We found that densities of floating life were higher inside the central NPGP than on its periphery,” they write.
The occurrence of plastic waste was also positively correlated with the abundance of three groups of floating sea creatures: sea rafts (Velella sp), blue sea buttons (Porpita sp), and violet sea snails (Janthina sp).
The researchers suggest that “subtropical gyres and other areas of high plastic concentration may be more than just garbage patches” and that “these regions may serve important ecosystem functions as ‘neuston seas.’”
“The possible overlap between garbage patches and neuston seas has important implications for established and emerging high seas impacts and activities,” they write.
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