More than 1,000 million tonnes of plastic waste flow into the ocean each year around the world, of which only 44 tonnes float on the surface of the ocean and most of the rest is unknown.It is thought that the product will eventually sink into the deep sea and plastic waste will accumulate on the bottom of the deep sea, but the actual condition of the deep sea waste has not been clarified.
Even in the waters near Japan, it is expected that an extremely large amount of plastic waste will be accumulated on the deep sea floor due to the transportation of waste leaked from East and Southeast Asian countries due to the Kuroshio Current moving northward.In particular, a group of the Japan Agency for Marine-Earth Science and Technology has set out to investigate the seabed of the "Kuroshio sequel / recirculation area" off the Boso Peninsula, which is one of the sea areas that are expected to form huge trash pools. rice field.
In September 2019, a manned submersible research vehicle "Shinkai 9" was used to survey the deep-sea plains about 6500 km off the Boso Peninsula and at a depth of 500 m.As a result, we found plastic waste that is orders of magnitude higher than similar deep water zones, especially disposable plastics such as plastic bags.The amount is large compared to depressions such as trenches and submarine canyons where garbage is likely to collect, and even almost intact food packaging manufactured over 6,000 years ago was found.This suggests that in the deep sea, plastics hardly deteriorate and may remain for a very long time.
According to this survey, a part of the large amount of waste carried by the Kuroshio will settle and deposit on the deep sea floor in the waters around Japan, and the deep sea floor of the "Kuroshio continuation / recirculation area" is one of the main collection points for plastic waste. It turned out to be one.Even on the surface layer of the "Kuroshio / Recirculation Area" off the coast of Shikoku, the ocean current circulates in a large swirl, so there is a possibility that the pollution of the seabed is spreading due to the accumulation and sedimentation of plastic waste caught in the vortex. It is said that the value is high, and it will be the subject of future research by this group.
Paper information:[Marine Pollution Bulletin] Massive occurrence of benthic plastic debris at the abyssal seafloor beneath the Kuroshio Extension, the North West Pacific
