Over 70% of deep-sea fish have ingested plastic, study finds

fish in laboratory being checked for plastic ingestion

Plastic pollution is affecting marine life in some of the most remote parts of the Atlantic Ocean with almost three quarters of a sample of more than 230 deep-water fish collected by NUI Galway scientists having ingested plastic particles.

The contamination level among the fish species, located in the northwest Atlantic thousands of kilometres from land and 600m down in the ocean, is one of the highest reported frequencies of microplastic occurrence in fish worldwide, according to the study published today in the journal Frontiers in Marine Science.

Microplastics are small plastic fragments that commonly originate from the breakdown of larger plastic items entering the ocean. Other sources may be waste water effluents carrying plastic fibres from clothing and microbeads from personal care products. Due to their low density, most of these microplastics float at the sea surface.

Midwater trawls

As part of the study the NUIG scientists participated in a transatlantic crossing onboard the marine institute’s Celtic Explorer vessel. During this research cruise they took dead deep-sea fish from midwater trawls such as the spotted lanternfish, rakery beaconlamp, stout saw-palate and scaly dragonfish.

The fish ranged in size from the smallest species the Glacier Lantern at 3.5cm to the largest species, the stout saw-palate at 59cm. Upon return to Galway the fish were inspected at the NUIG’s Ryan Institute for microplastics in their stomach contents.

PhD candidate and lead author Alina Wieczorek said: “Deep-water fish migrate to the surface at night to feed on plankton [microscopic animals] and this is likely when they are exposed to the microplastics.”

One of the inspected spotted lanternfish, which was 4.5cm in size, had 13 microplastics extracted from its stomach contents. The identified microplastics were mostly fibres, commonly blue and black in colour.

In total, 233 fish were examined and 73 per cent had microplastics in their stomachs, “making it one of the highest reported frequencies of microplastic occurrence in fish worldwide”.

Internal damage

Previous studies have shown microplastics can be ingested by numerous marine animals from zooplankton to worms to fish. The ingestion of microplastics may cause internal physical damage, inflammation of intestines, reduced feeding and other effects.

What is also of concern, Ms Wieczorek said, was that many of these ingested microplastics have associated additives, such as colourants and flame retardants that are added to plastics during production process, and/or pollutants that are adsorbed on to the microplastics from the sea.

“There is now evidence that some of these toxins on the microplastics can be transferred to animals that eat them, with potential harmful effects.”

Co-author Dr Tom Doyle of the Ryan institute at NUIG, said: “It’s worrying to think that our daily activities, such as washing our synthetic clothes in our washing machines, results in billions of microplastics entering our oceans through our waste water stream that may eventually end up in these deep sea fishes.”

Polluted patch

The fish were sampled from “a warm core eddy”, which is a circular current in the northwest Atlantic Ocean. Similar to what are known as ocean gyres, these currents are now thought to accumulate microplastics and that the sampled fish may have originated from a particularly polluted patch of the Atlantic.

Ms Wieczorek added: “This would explain why we recorded one of the highest abundances of microplastics in fishes so far, and we plan to further investigate the impacts of microplastics on organisms in the open ocean.”

The research was carried out within the Plastox project, a European collaborative effort to investigate impacts of microplastics in the marine environment under the JPI Oceans framework and supported by the iCRAG (Irish Centre for Research in Applied Geoscience) project, funded by Science Foundation Ireland.

The study can be read at: http://bit.ly/2EEmMHI