10 million tonnes of plastic enter the ocean every year, mainly through rivers but as it turns out most plastic is not floating on the ocean surface.
Sea surface accumulations only account for 1% of the estimated marine plastic budget while microplastics account for 3.5 %. All the plastic that is seen in locations like the great pacific garbage patch is just the tip of the iceberg.
Just off the coast of Italy in the Mediterranean Sea the university of Manchester found a concentration of 1.9 million microplastic pieces per square metre (4 pieces/gram) on the ocean floor. Perhaps more disturbingly is that all seafloor samples that were taken contained microplastics.
The microplastics (fragments smaller than 1mm) are being concentrated in specific locations on the ocean floor by powerful currents, at a depth 600 to 900m, where the currents have the greatest interaction with the seafloor.
These ‘thermohaline-driven currents’, naturally build large accumulations of sediment on the seafloor but it has been shown that they also control the distribution of microplastics.
On the surface the currents concentrate plastics into giant floating garbage patches, below the surface they move and settle heaps of microplastics into biodiversity hot spots and owing to their small size, microplastics can be easily ingested by organisms of all sizes increasing transfer of harmful toxic substances throughout the food web and to us.
Have a wonderful day.
HAQUA Research Dept.