There may no longer be any perfectly clear seas anymore – when JAMSTEC’s(Japan Agency for Marine Earth Science and Technology)deep sea submersible vehicle conducted its first observation of the deep ocean floor, the first object to strike the investigator’s eye was a piece of garbage.
There is an important ecosystem in the deep sea. Since sunlight cannot penetrate to the deep sea floor, the deep sea ecosystem is very different from one that depends on photosynthesis, which produces organic matter using sunlight. This so-called deep sea chemosynthesis ecosystem can synthesize organic matter from methane and hydrogen sulfide bubbling up from the ocean floor. Because of the features of this particular ecosystem, some researchers believe that the dark abyssal region of the sea is the origin of life.
Scientists also believe that there are many unknown deep sea ecosystem sites still in existence. In fact, new marine life is being increasingly discovered; however, at the same time, a lot of garbage is also being found in unexpected areas of the sea.
It has been announced that scientists have found that deep sea sediment core samples collected from the deep seabed (1,000 to 3,500 m depth) in the North Atlantic, the Mediterranean, and the Southwest Indian Ocean contain a massive amount of blue and red plastic fibers(Woodall et al. 2014).
These core samples were taken from 12 sites, and all of them contained tiny plastic fragments. After carefully investigating the result of these spot checks, researchers have concluded that plastic debris exists ubiquitously all over the deep seafloor.
These plastics found on a seabed were, of course, originally floating at the ocean’s surface. Probably more than 250,000 tons of plastics are currently floating on the surface of the world’s oceans (Eriksen et al. 2014) , but there may be a lot more plastic deposited on the deep-sea floor.
There is no clear overview of how much plastic debris lies deep in the ocean floor right now, but research has revealed a maximum of 40 grains of microplastic in a 50 ml sample of mud collected from the Indian Ocean (Woodall et al. 2014).
At 50 ml, this amount is about one-third of a small teacup. It seems so little, and yet this level of plastic pollution in the Indian Ocean is frightening. It is actually 10,000 times higher than the pollution observed in a gyre, where plastic debris gathers on the surface layer of the ocean (Woodall et al. 2014).
The average amount of plastic debris found on the deep seafloor is about twice as much as on the shallow seafloor. To be precise, plastic debris is accumulating more in the deep ocean than in the shallow ocean.
Microplastics are well known for adsorbing persistent organic pollutants (POPs) such as DDT and PCBs. Scientists hypothesize that, over time, such contaminated microplastics are eaten by marine animals and are incorporated into the food chain; however, the full extent and consequences are hard to quantify.
Even if from now on we stop plastic waste from entering the sea, the plastic that is already there will accumulate at increasing depth in the oceans, because a vast amount of microplastics are already bobbing between the waves, raring to go from the ocean surface to the deep sea.