Many of the biggest threats to our health come in the form of invisible microbes, the latest example being the novel coronavirus that originated in Wuhan, China. The same is true for the health of the environment: imperceptibly small microplastics can pose serious risks to ecosystems both on land and in water.
However, microplastics have been saturating nature to an alarming degree. Blown by the winds, these tiny particles have even reached the top of mountains. Driven by ocean currents and facilitated by gravity, they have also settled to the bottom of the oceans.
Recently, a team of researchers from the Scripps Institution of Oceanography discovered that there could be a million times more pieces of plastic in the ocean than previously thought. According to their new estimates, ocean water contains up to 8.3 million pieces of mini-microplastics per cubic meter, which is five to seven orders of magnitude more than previous estimates.
"For years we have been doing microplastics studies in the same way, using a net to collect samples," explained one of the researchers, Jennifer A. Brandon. "But something smaller than that mesh network has escaped."
Now comes more proof that microplastic pollution has reached endemic levels in the oceans. New research by an international team of scientists has found that up to 1.9 million pieces of plastic have formed in a thin layer in just 1 square meter at certain points on the seabed.
This is one of the highest levels of microplastic pollution ever recorded in ocean water. According to scientists, these microplastics deposited on the seabed come mainly from fibers used in textiles and clothing. These particles are largely left unfiltered by domestic wastewater treatment plants, from where they enter rivers and oceans, spreading everywhere.
Scientists have also shown that currents near the ocean floor, known as near-bed thermohaline currents, play an important role in how microplastics travel to the seafloor. "These currents are known to supply oxygen and nutrients to deep-sea benthos, suggesting that deep-sea biodiversity hotspots may also be microplastic hotspots," the researchers explain.
These undersea currents can lead to the accumulation of microplastics in large quantities in sediments at selected submarine microplastic hotspots. These deep-sea hot spots are the equivalents of the giant garbage patches that float like huge eyes on the surface of the oceans driven by surface currents.
"Almost everyone has heard of the infamous 'garbage patches' of floating plastic in the ocean, but we were surprised by the high concentration of microplastics we found on the seafloor," says Ian Kane, a geologist at the University of Manchester and lead author of the new study.
“We found that microplastics are not evenly distributed in the study area; instead, they are distributed by powerful currents on the seabed that concentrate them in certain areas ”, adds Kane.
Deep sea currents play a key role in transporting oxygen and nutrients from the surface to the seafloor, where unique ecosystems often thrive. However, they are now also helping the accumulation of tiny plastic particles on the ocean floor, which is sure to interfere with the forms of marine life there. The effects of massive plastic pollution on the ocean floor have yet to be fully studied and understood.
"It's unfortunate, but plastic has become a new type of sediment particle, which is distributed across the seabed along with sand, mud and nutrients," laments Florian Pohl, scientist at the Department of Earth Sciences of the Durham University in the UK.