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.