Guest essay by Eric Worrall

Scientists have discovered Antarctic Krill can digest or at least break up lumps of plastic into even smaller lumps – but when the krill were force fed large quantities of radioactive plastic over an extended period their ability to digest plastic deteriorated.

Krill found to break down microplastics – but it won’t save the oceans Digestion of plastic into much smaller fragments ‘doesn’t necessarily help pollution’, Australian researchers say A world-first study by Australian researchers has found that krill can digest certain forms of microplastic into smaller – but no less pervasive – fragments. The study, published in Nature Communications journal on Friday, found that Antarctic krill, Euphausia superba, can break down 31.5 micron polyethylene balls into fragments less than one micron in diameter. … Unfortunately, Dawson said, krill were unlikely to provide a solution to the levels of plastics and microplastics polluting the oceans. “It’s not necessarily helping plastic pollution, it’s just changing it to make it easier for small animals to eat it,” she said. “It could be a new source of plastics for the deep ocean.” A study by Newcastle University in December found microplastics in the stomachs of deep-sea creatures from 11km deep trenches in the Pacific Ocean. Dawson said microplastics that had been digested by krill were also too small to be detected in most oceanic plastic surveys, meaning the level of microplastics in the ocean could be higher than currently assumed. …

Read more: https://www.theguardian.com/environment/2018/mar/12/krill-can-turn-microplastics-into-nanoplastics-study

The abstract of the study;

Turning microplastics into nanoplastics through digestive fragmentation by Antarctic krill Amanda L. Dawson, So Kawaguchi, Catherine K. King, Kathy A. Townsend, Robert King, Wilhelmina M. Huston & Susan M. Bengtson Nash Microplastics (plastics <5 mm diameter) are at the forefront of current environmental pollution research, however, little is known about the degradation of microplastics through ingestion. Here, by exposing Antarctic krill (Euphausia superba) to microplastics under acute static renewal conditions, we present evidence of physical size alteration of microplastics ingested by a planktonic crustacean. Ingested microplastics (31.5 µm) are fragmented into pieces less than 1 µm in diameter. Previous feeding studies have shown spherical microplastics either; pass unaffected through an organism and are excreted, or are sufficiently small for translocation to occur. We identify a new pathway; microplastics are fragmented into sizes small enough to cross physical barriers, or are egested as a mixture of triturated particles. These findings suggest that current laboratory-based feeding studies may be oversimplifying interactions between zooplankton and microplastics but also introduces a new role of Antarctic krill, and potentially other species, in the biogeochemical cycling and fate of plastic.

Read more: https://www.nature.com/articles/s41467-018-03465-9

The expression of concern about nano-plastic seems a stretch. Breaking micro-plastic into smaller chunks, making it available to even more versatile and varied microorganisms further down the food chain, is likely enough to effect complete clearance. Anyone who has ever owned a boat knows how difficult it is to protect fuel from contamination by the ubiquitous fungus and bacteria which thrives in sea water. It seems highly likely that at least one other organism, somewhere in the world’s oceans, has developed a taste for our plastic waste.

Correction (EW): the plastic wasn’t radioactive, I misread “Triturated” as “Tritiated” (h/t Phil)

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