Plastic waste in the ocean


Fishing nets, packaging bags and other debris threaten wildlife in some coral reef ecosystems deep in the ocean.

A survey of 84 coral reef ecosystems at 25 sites in the Pacific, Atlantic and Indian ocean basins found that plastic debris brought by human activities is almost everywhere, in both shallow and deep waters.

The team, led by marine biologist Hudson Pinheiro from the University of São Paulo in Brazil, set out to investigate the biodiversity of remote coral reefs, which researchers expected to remain pristine. But during their sampling they noticed that "these places were not as pristine as we thought," Pinheiro said. The results showed that 77 of 84 ecosystems contained large plastics - plastic items 5 centimeters or more in diameter. Researchers found that this type of plastic makes up 88% of all human-generated trash on coral reefs

Many of the debris found in more remote areas are discarded fishing gear, including nets and lines. In some places, the team found evidence of "ghost fishing," where abandoned fishing nets tangled in coral reefs are still catching and killing fish.

In non-coral reef marine ecosystems, human-made plastic waste is usually concentrated near the sea surface, mainly various consumer products. But coral reefs are different—Pinheiro and colleagues found that deeper reefs contain more large plastics than shallower ones. This could be for a variety of reasons, such as stronger waves on shallow reefs, which may carry plastic away and push it deeper. And plastic removal is mostly done on shallow reefs.

Deep-water coral reefs are home to a large number of fish species, which may explain why so much fishing net gear is found in these ecosystems. As there are fewer fish in shallow waters, deep-sea fishing has become more common, and the amount of trash found here may reflect this. "Because of the pollution and degradation of shallow reefs, fishermen have to move further from the coast and fish in deeper reefs," Pinheiro said.

Plastic waste damages coral ecosystems in many ways. Ropes, nets, etc. can become entangled in corals and cause breakage. Plastic debris can also harbor bacteria and other microorganisms that can damage corals. "There have been other studies linking the presence of plastic to coral disease," Pinheiro said.

As the United Nations negotiates an international treaty to eliminate plastic pollution, people need to consider how to eliminate this type of deep-sea pollution. “We’re not talking about going to the supermarket and exchanging plastic bags for paper ones, we’re talking about people who depend on fishing for food,” Pinheiro said, urging negotiators to consider discussing subsidies and other initiatives to help fishermen use less plastic, or Develop biodegradable materials to help end pollution of the deepest coral reefs.

Roisin Greene, co-director of the World Economic Forum's Global Plastics Action Partnership (GPAP), which works with business organizations and governments to find solutions to plastic pollution, said GPAP's perspective is focused on the spread of plastic on land. The paper provides "a better understanding of the consequences of plastic leaking into the environment." This information is important to ensure that organizations like GPAP can provide the best advice.