Swimming in Plastic

On my commute last week I came across an article addressing the fact that microplastics have been found in humans for the first time. Plastics have previously been found in the guts of fish and also in tap water so this news has not come as a great surprise; but how did the plastic get there and what are we doing to stop it? This trilogy of blog posts will look into the effects of plastic waste in our oceans and what impacts this is having on us humans.

The concept of a plastic cycle has been introduced and given similar processes and stages as a biogeochemical cycle, such as the hydrological cycle or the carbon cycle. As with any other cycle the plastic first has to enter the system. Plastic that has been created can be from a terrestrial source or from an ocean-based source.

The land-based plastics come mainly in the form of microplastics which are missed in the filtration system of waste water treatment; these land-based plastics make up approximately 80% of the plastics found in the ocean. Ocean-based plastics can be accidental or purposeful. For example a shipping container may have a spillage or fishing fleets may dump debris directly into the ocean.

Figure 1. Concentration of plastic in surface waters in the oceans. Coloured dots demonstrate mass concentration areas. Grey areas represent accumulation sites. Source: Cózar et al., 2014.

Despite where the plastic derives from, the improper disposal of the waste causes mass accumulation zones in gyres. Gyres are the result of the wind patterns around the globe, the position of land masses and Earth’s rotation; there are five in total. The concentration of plastic debris in the oceans can be seen in figure 1. Once plastic is in the gyres it goes through the process of weathering by wind and waves but also hydrolysis and UV degradation.

Figure 2. Rubber ducked washed ashore. Source: MNN.

Knowledge was improved about how these gyres circulate waste due to the adventures of 28,000 rubber ducks. In 1992 a shipping container bound for the United States was lost at sea resulting in its cargo to be released into the ocean. Ducks from this shipment are still washing up around the world today with some being found in Hawaii, Alaska and even Scotland. The ducks turning up in good condition over 20 years after their great plunge into the ocean highlights the longevity of plastic. It is believed that at least 2,000 of the ducks are still circulating in the North Pacific Gyre; what is known as the Great Pacific Ocean Garbage Patch. Whilst it is hard to measure, it is thought that the total weight of microplastics in the North Pacific is 21 x 10^8 tons; that is the weight of approximately 150,645,624 London buses in the North Pacific alone!

Figure 3. Travel patterns of the rubber ducks. Source: MNN.

Once the plastic finds itself within the ocean it will eventually start to break down by the aforementioned methods. Plastic floating around the ocean can create a new habitat, known as a plastiphere, and increase the items density as a result of organisms growing on the material causing sinking into the deeper ocean. This means that areas that we thought could remain untouched from the pollutant are impacted. Early this year plastic was found at the bottom of the Mariana Trench.

Next week I will look into the impacts this is having on wildlife and what this means ultimately for us humans.