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How coastal species are living on plastic debris in the ocean

Context: Plastic trash is abundant in our urban refuse, rivers, and forests, from the slopes of the highest peaks to the depths of abyssal trenches. A new study by researchers from Canada, the Netherlands, and the U.S. has reported that coastal lifeforms have also colonised plastic items in the ocean

“The Anthropocene epoch” is the name some scientists have proposed for a new period in history characterised by the influence of one species on the planet’s geology, ecosystems and even its fate — none other than Homo sapiens.

When did it began?

• Scientists are still figuring out when this epoch really began; some candidates include the first nuclear weapon test and rapid industrialisation after the Second World War.
• Another contender is the creation of plastic trash which is abundant in our urban refuse, rivers, and forests, from the slopes of the highest peaks to the depths of abyssal trenche
• Ocean life has washed ashore at beaches with stomachs of plastic debris. Plastic has provided ample evidence of its persistence in the natural universe, but of late, scientists have also been uncovering evidence that it is becoming one with nature in troubling new ways.

The Great Pacific Garbage Patch

• There are some water currents in the ocean that, driven by winds and the Coriolis force, form loops. These are called gyres.
• The North Pacific Subtropical Gyre (NPSG) is one such, located just north of the equator in the Pacific Ocean.
• It consists of the Kuroshio, North Pacific, California, and North Equatorial currents and moves in a clockwise direction.
• These currents flow adjacent to 51 Pacific Rim countries. Any trash that enters one of these currents, from any of these countries, could become part of the gyre.
• It contains an estimated 45,000-1,29,000 metric tonnes of plastic, predominantly in the form of microplastics.
• The numerical density of plastics here is around four particles per cubic metre. Mass-wise, however, heavier, more visible objects that haven’t yet broken down into smaller particles accounted for 92% of the plastics in 2018.

The study

• From November 2018 to January 2019, researchers collected 105 pieces of plastic debris from the eastern part of the NPSG, which is considered “the most heavily plastic-polluted ocean gyre on the globe,”
• Based on studying them, they reported that 98% of the debris items had invertebrate organisms.
• They also found that pelagic species (species of the open ocean) were present on 94.3% of them and coastal species on 70.5%.
• The number of coastal species such as arthropods and molluscs identified rafting on plastic was over three-times greater than that of pelagic species that normally live in the open ocean.
• In all, they found organisms belonging to 46 taxa. While 37 of them were coastal, the rest were pelagic.
• Among both coastal and pelagic organisms, crustaceans were the most common. The coastal species were most commonly found on fishing nets whereas the pelagic species on crates.

The relevance of the findings

• The researchers have written in their paper that “the introduction of a vast sea of relatively permanent anthropogenic rafts since the 1950s” has given rise to a new kind of “standing coastal community in the open ocean”. They’ve named it the neopelagic community.
• They write in their paper that while coastal species have been found on human-made objects in the open ocean before, they were always considered to have been “misplaced” from their intended habitats. The neopelagic community, on the other hand, is not misplaced but lives on plastic items in the garbage patch, including reproducing there.
• The finding recalls a study published on April 3, in which researchers reported that polyethylene films had chemically bonded with rocks in China. This, in turn, is reminiscent, of the “anthropoquinas” of Brazil (sedimentary rocks embedded with plastic earrings) and the “plastiglomerates” of Hawai’i (beach sediment + organic debris + basaltic lava + melted plastic).