Saturday, 16 Feb 2019

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Scientists' plea on threat to ocean giants

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Health Desk: 06 February 2018: Scientists are calling for research on the impacts of microplastics on whales, sharks, and rays that strain tiny food, like plankton, out of seawater. They say the ocean giants face "significant risks" from microplastics.

The Gulf of Mexico, the Mediterranean Sea, the Bay of Bengal and the Coral Triangle are priorities for monitoring, according to a review of studies.

Researchers from the US, Australia, and Italy looked at data on threats to large filter feeders from microplastics. These small plastic pieces less than five millimeters long can be harmful to the ocean and aquatic life.

Contamination from microplastics has the potential to further reduce the population sizes of the large filter feeders, they say.

"The full magnitude of risks of ingesting microplastics are yet to be fully investigated," said Elitza Germanov of Murdoch University, Australia, and researcher at the US Marine Megafauna Foundation.

Possible risks include reduced nutritional uptake and damage to the digestive system when microplastics are ingested, she said.

In addition, toxin exposure through plastic ingestion could affect many biological processes, such as growth and reproduction, putting filter feeding populations "under even more strain", she added.

Microplastics are similar in size and mass to many types of plankton. Studies have shown chemicals associated with plastics in the bodies of whale sharks and fin whales. Estimates suggest some whales may be ingesting hundreds of fragments of plastic a day.

A number of filter-feeding sharks, rays, and whales are on the edge of extinction. Many are long-lived and give birth to few offspring during their lives. The whale shark, for example, is listed as Vulnerable on the IUCN Red List.

Found in tropical and warm temperate waters, it is the largest fish in the world, yet feeds on tiny plankton, crustaceans and small fish, reports BBC.

The study, published in the journal Trends in Ecology and Evolution.