Water Pollution: The Abyssal Plain

The abyssal plain is a cold and dark place which is located between 3000/4000 and 6000 meters below the sea surface and called a relatively deep sea-floor. While studies usually indicate that deep-sea is flat-plain habitat layer known as abyssal zone and oceanic trenches like the Marina Trench are made from steep valleys that go even deeper (Trenches might reach 11,000 km depth). The latter zone mentioned is called hadal zone.

If two zones are compared, the abyssal zone is much more like a one huge habitat whereas hadal trenches are tiny islands and they cover less 1% of the earth’s surface. Each hadal zone island can have their own unique endemic fauna.

Figure 1. Anemones and Nankai Trough (copyright belongs to the Japan Agency for Marine-Earth Science and Technology)

In Nankai Trough, at approximately 3848 m depth, sea anemones were observed as they settled on some plastic. At this depth, since the habitat becomes quite diverse, it is really complex to predict what might happen after this interaction, and some of the results we will see in time might be unexpected.

Additionally, in one of the studies (Chiba and their team), 16 % of the recording proved the sight of plastic in the vicinity of deep-sea organisms such as ray-finned fish and sea anemones, which were often attached to the plastic garbage. The recording even indicated that deep-sea mollusks were entangled with plastic bags in the Japan Trench, where at a depth of 8,046 meters (26,400 feet).

While soft plastics like bags can harm the animals by smothering them, hard plastics can give some animals like anemones an unfair advantage. For example, creatures such as sea anemones need hard surfaces, typically rocks to settle on and grow. However when hard plastics become a habitant in this vicinities, sea anemones starts to have extra places to hold on. One of the study’s findings was that that even in places with no rocky surfaces, sea anemones were able to settle down on hard plastic. This could potentially cause them to become the new invasive species.

However, the Mariana Trench is also surprisingly polluted for being so remote. A study found that crustaceans pulled from the depths were more contaminated with the pollutants that survived I this depth than animals found in China’s most polluted rivers. The organisms had high levels of persistent organic pollutants (POPs) like PCBs. These compounds can persist in the environment for hundreds of years.

Figure 2.Plastic Pollution in Mariana Trench

According to a recent estimations in one area of the Pacific, the area started to be called as the “Great Pacific Garbage Patch,” contains 79,000 metric tons of mostly plastic trash.

Figure 3. A deep sea crab in Toyama Bay/ Sea of Japan. Image credit: Japan Agency for Marine-Earth Science and Technology (JAMSTEC).   

        

“Why Japanese deep-sea is a front target for these plastics?  A previous study (Jambeck et al. 2015) estimated the top 20 contributors of mismanaged plastic waste available to enter the ocean in 2010. Countries placed on the Asian continent represented 12 of the top 20 of these countries, with China way out ahead of the pack. Japan is located in the area where a large amount of plastic waste is transported from these massive waste producers via ocean currents such as Kuroshio, so the seas around Japan could be a hotspot of plastic debris. ” 

Although several countries have pledged to implement bans on plastic usage starting with single-use plastics nationally (regarding the call of United Nations Assembly), the resolutions are non-binding.

 

References

[1]	B. Sridharan, "Mongabay," 28 June 2018. [Online]. Available: https://news.mongabay.com/2018/06/the-plastic-crisis-sinks-to-a-new-low-in-the-deep-sea/. [Accessed 17 April 2022].
[2]	Lisbdnet, "Lisbdnet," 1 December 2021. [Online]. Available: https://lisbdnet.com/what-is-at-the-bottom-of-the-ocean-floor/. [Accessed 17 April 2022].
[3]	J. Daley, "Smithsonian," 11 May 2018. [Online]. Available: https://www.smithsonianmag.com/smart-news/study-shows-deepest-parts-ocean-are-polluted-plastic-180969049/. [Accessed 17 April 2022].
[4]	M. Campbell, "Applied Sciences," 28 April 2021. [Online]. Available: https://www.technologynetworks.com/applied-sciences/news/single-use-plastics-found-at-the-deepest-points-of-the-ocean-348206. [Accessed 17 April 2022].
[5]	T. M. Y. A. e. a. Nakajima R, "Massive occurrence of benthic plastic debris at the abyssal seafloor beneath the Kuroshio Extension, the North West Pacific," Marine Pollution Bulletin, no. 112188, 2021.