Great Pacific Garbage Patch

Subject: Environment

Section: Pollution

Context: In the Great Pacific Garbage Patch, coastal life piggybacks on plastic trash.

What is the Great Pacific Garbage Patch?

There are some water currents in the oceans 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.

Inside this gyre, just north of Hawaii, lies a long east-west strip where some of the debris in these currents has collected over the years. The eastern part of this is the Great Pacific Garbage Patch. It is, per one estimate, 6 million sq. km big and more than 50 years old.
The patch 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 4 particles per cubic metre. Mass-wise, however, heavier, more visible objects that haven’t yet broken down into smaller particles accounted for 92% in 2018.

What did the new study find?

The tsunami off the Japanese coast in 2011 contributed to the debris in this garbage patch. Until at least 2017, researchers had found debris washing ashore on the West coast of North America containing live lifeforms originally found in Japan.
From November 2018 to January 2019, researchers collected 105 pieces of plastic debris from the eastern part of the NPSG, “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 (i.e. of the open ocean) were present on 94.3% of them and coastal species, on 70.5%. That is, organisms found on coasts were getting by on small floating islands of garbage (to humans) out in the Pacific Ocean.
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, and 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.

What do the findings mean?

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 – which is reminiscent, in turn, 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).

Aquatic Zones

The littoral zone is the shallow water near the shore. In the ocean, the littoral zone is also called the intertidal zone.
The pelagic zone is the main body of open water farther out from shore. It is divided into additional zones based on water depth.
- In the ocean, the part of the pelagic zone over the continental shelf is called the neritic zone, and the rest of the pelagic zone is called the oceanic zone.
The benthic zone is the bottom surface of a body of water. In the ocean, the benthic zone is divided into additional zones based on depth below sea level.