Thursday, August 21, 2014

Implications of the Continually Growing Accumulation of Microplastics in the World’s Oceans

In an article appearing in the journal Science, authored by Kara Lavender Law of the Department of Oceanography at Woods Hole, Massachusetts and Richard C. Thompson of the School of Marine Science and Engineering at Plymouth University UK, attention is drawn to microplastics in the world's oceans. 

Although the focus of the pollution of the marine environment with plastics is usually on the unsightly appearance of this detritus, there is now growing concern among the scientific community of the presence of so-called, “microplastics” – particles of plastic so small as to be essentially undetectable by the eye.  Microplastics have been used to describe particles smaller than 5 mm in diameter (where 5 mm = .197 inches).  This particular population of marine pollutants is ever-growing due to the ineluctable degradation of plastic pollutants to microplastic-sized particles. 

One of the chief environmentally-based concerns is focused on the fact that particles of this size are readily ingested by organisms as small as zooplankton – organisms that play a crucial role in the marine food chain. The sources for microplastics in the marine ecosystem are manifold including –
·         Degradation of larger items entering rivers through runoff, tides, wind and catastrophic events such as tsunamis, hurricanes and earthquakes
·         Cargo lost at sea and other debris originating from on board ocean vessels
·         Microplastic-size particles such as cosmetic beads and clothing fibers that on account of their size can readily pass through waste water treatment facilities.

Once in the oceans these particles are passively transported by many and diverse factors.  They are found ubiquitously in coastal sediments around the world and, as stated previously, are readily ingested by many types of marine organisms including mussels that can retain these particles long after ingestion.  The impact of the presence of these particles on the biology of the organisms that ingest them is not clearly understood.
One of the more disturbing properties of microplastics is their propensity to adsorb environmentally harmful chemicals such as dichlorodiphenyl-trichloromethane (DDT) and polychlorinated biphenyls (PCBs) on their surface and consequently passively concentrate these dangerous substances.

Although the real risk of the presence of microplastics upon the health of the marine ecosystem is exceedingly difficult to ascertain, it is certainly worthy of further study.

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