Oceans: a plastic soup

Seas and oceans of the Earth Planet more and more looks like a plastic soup. Pictures like the next one will be more frequently seen if we don’t stop the plastic pollution. In this post we are talking about the amount of plastics in the oceans, according to the findings recently published in Plos One. 

INTRODUCTION

Plastic pollution is a phenomenon present in all oceans due to the floating capacity and its durability, as some kinds of plastic can remain in the water for 400 years. Thanks to photodegradation (degradation induced by light) and other weathering processes, plastics breaks into smalls pieces and are scattered through the ocean, and finally they arrive to the oceanic gyres, but also they become accumulated on closed bays, gulfs and seas surrounded by important populations.

There are five oceanic gyres: North and South Atlantic, North and South Pacific and Indian. An ocean gyre is a large system of rotative marine currents, related with the rotational movement of the Earth. (NOAA, Creative Commons)

These plastics have a negative effect on the marine environment, affecting the small organisms of the plankton till the big whales, since they feeds on plastic items or they get entangled. An associated problem is that plastic absorbs persistent organic pollutants, and these are transferred along food chains.

WHICH IS THE AMOUNT OF PLASTIC IN THE OCEANS?

According to a recent research, it has been estimated that there are about 5.25 trillions of plastic particles in the oceans, what suppose a weight of about 268,940 tones. The amount of plastic found in this study is just a 0.1% of the total annual production. In addition, on the one hand, the northern hemisphere contains the half of plastic (55.6% of the particles and 56.8% of the weight), being the North Pacific the zone with the biggest accumulation (37.9% and 35.6% respectively). On the other hand, in the southern hemisphere is the Indian Ocean which accumulates more plastic than others. These results show that, in spite of the population density is higher in the coasts of the northern hemisphere, plastics are spread all over the world thanks to currents and wind. An alternative explanation could be that there are unknown pollutant sources.

About 92.4% of the particles are microplastics (between 0.33 and 4.75 mm), coming from bigger ones.

Distribution of plastics in the oceans: small microplastics (0.33-1.00 mm), big microplastics (1.01-4.75 mm), mesoplastics (4.76-200 mm) and macroplastics (>200 mm). The colours express the plastic density (particles/m2). (Eriksen et al. 2014, Creative Commons)

The study show that, amongst macroplastics, the most common pieces were made of foamed polyethylene (see the picture), but buoys in weight.

The investigation determines that there is an important loss of plastics in the sea surface, specially in the northern hemisphere. The processes implicated are: photodegradation with UV, biodegradation, ingestion by organisms, loss of buoyancy, burial in the sea-floor and beaching.

This publication is under a Creative Commons licence:
Licencia Creative Commons Atribución-NoComercial-CompartirIgual 4.0 Internacional.

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