Highest Level of Microplastics on Seafloor Discovered

Published on

May 7, 2020

Microplastics

Microplastics in water (stock image).
Credit: © dottedyeti / Adobe Stock

An international research project has revealed the peak levels of microplastic ever recorded in the seabed, with up to 1.9 million pieces in a thin layer covering 1 square metre.

Research found that over 10 million tons of plastic debris enter the ocean annually. Floating plastic debris has successfully caught the attention of the ‘Blue Planet Effect’, while, movie producers and environmentalists take a keen interest in disclose the detrimental effects plastic has on the planet and hoping to curb the excess usage plastic, especially straws and carrier bags are yet to make a huge impact on society. However, the above accumulations account for less than 1% of the plastic that enters the world’s oceans.

The remaining 99% is believed to be resting in the deep ocean. It wasn’t clearly confirmed until now. The journal Science, the research conducted by The University of Manchester (UK), National Oceanography Centre (UK), University of Bremen (Germany), IFREMER. These currents can concentrate microplastics within huge sediment accumulations, which they termed ‘microplastic hotspots’. The hypothetical hotspots accumulate garbage in patches as a result of the currents on the ocean surface.

Dr Ian Kane of The University of Manchester quoted “Almost everybody has heard of the infamous ocean ‘garbage patches’ of floating plastic, but we were shocked at the high concentrations of microplastics we found in the deep-seafloor.

CREDIT: Getty

“We discovered that microplastics are not uniformly distributed across the study area; instead they are distributed by powerful seafloor currents which concentrate them in certain areas.”

The seafloor, which is mainly comprised of fibres contain micoplastics from textiles and clothing despite many countries having wastewater treatment plants.

Once the micrplastics fall into the ocean they either settle out slowly or can be transported rapidly by episodic turbidity currents — powerful underwater avalanches — that travel down submarine canyons to the deep seafloor.

Once the microplastics settle into the deep sea they are driven to the sea bed by ‘bottom currents’ that tend to concentrate fibres and fragments with large drifts of sediment.

Oxygenated water and nutrients also house important ecosystems that can consume or absorb the microplastics.

According to a study conducted by the University of Manchester, the first direct link between the behaviour of the ocean currents and the concentrations of seafloor microplastics and the findings will help to predict the locations of other deep-sea microplastic hotspots and direct research into the impact of microplastics on marine life.

The research team managed to gather sediment samples from the seabed of the Tyrrhenian Sea (part of the Mediterranean Sea) and combined these with calibrated models of deep ocean currents and detailed mapping of the seafloor.

Once the samples were collected the microplastics were separated from the sediment, counted under a microscope and analyzed using infra-red spectroscopy to determine the plastic types.

The team were subsequently able to illustrate the behaviour of the ocean currents and their impact on the distribution of microplastics on the seabed.

Dr Mike Clare of the National Oceanography Centre, who was a co-lead on the research, stated: “Our study has shown how detailed studies of seafloor currents can help us to connect microplastic transport pathways in the deep-sea and find the ‘missing’ microplastics. The results highlight the need for policy interventions to limit the future flow of plastics into natural environments and minimise impacts on ocean ecosystems.”

Dr Florian Pohl, Department of Earth Sciences, Durham University, said: “It’s unfortunate, but plastic has become a new type of sediment particle, which is distributed across the seafloor together with sand, mud and nutrients. Thus, sediment-transport processes such as seafloor currents will concentrate plastic particles in certain locations on the seafloor, as demonstrated by our research.”