As part of the University of Western Australia (UWA) Inquiring Minds Series, Oceans Institute Director Carlos Duarte, along with UWA PhD student Julia Reiser, presented findings that give a global picture of plastic concentrations in the world’s oceans.
Computer modeling indicated that plastic debris should accumulate in central gyres of the ocean, or, in other words, stagnant areas of water that are unaffected by currents around coastal areas. Until the study, only one around the Pacific Ocean had ever been studied.
To build a global picture, the Oceans Institute used the aggregate of minute aquatic organisms that float or swim in the surface film of a body of water captured in Neuston samplers to skim the top 10cm of the ocean and collect samples containing small buoyant plastic particles in collaboration.
The particle concentration in the gyres was 100 to 1000 times greater than in the rest of the ocean.
One big surprise for the researchers is that they were expecting values in excess of one million tonnes of plastic and only found between 10 and 30,000 tonnes of plastic. According to Dr. Duarte and Ms. Reiser, this means plastic is being lost somewhere. The pathways of loss included particles breaking into smaller and smaller pieces due to UV radiation, degradation by bacteria, and abundant organisms acting as a sink for the particles.
The fish, which are found in the ocean’s gyres, come to the surface to feed at night and ingest broken down plastic particles since they are about the size of their usual prey.