More than half a month after the paper was published in early February, Dr. Song Xikun of the State Key Laboratory of Offshore Marine Environmental Sciences at Xiamen University and Peng Xiaotong, a researcher at the Institute of Deep-sea Science and Engineering of the Chinese Academy of Sciences, will receive emails from journalists from all over the world from time to time. From academic journals such as Nature to social media, their recent findings have raised concerns about marine environmental protection.
Together with domestic and foreign collaborators, they discovered plastic "oases" deep in the South China Sea. The vast deep-sea soft-facing seabed is often considered the "desert" of life.
"Large plastic piles are becoming a new hotspot for biodiversity on the deep seabed," reads a cover paper published in Environmental Science and Technology Letters.
Benthic biomes found on deep-sea plastic surfaces
Unexpected: plastic biomes found on the deep seabed!
In July 2018, as one of the instructors, Song Xikun took the "Jiageng" research vessel to participate in the first "Haisi Xuetang" voyage of Xiamen University to carry out undergraduate marine science internship in the South China Sea. While sailing through the Luzon Strait, more than a dozen college students collected the first plastic sample from the study through benthic trawls. They were surprised to find that the piece of plastic had dozens of egg sacs of deep-sea shellfish attached to it.
In the next 3 voyages, such "adventures" continued.
"Some animals obtained through trawling are easy to identify, such as starfish. But most of the organisms attached to the plastic are small and need to be observed and identified with the help of stereo microscopy. Gu Yifan, an undergraduate student at Xiamen University Malaysia who participated in the sea sampling, said, "What impressed me most was the collection of a plastic bottle with a small dark horn on it, which is easy to ignore without looking closely - this is a jellyfish hydra body." ”
As early as May 2018, when Peng Xiaotong took the "Deep Sea Warrior" deep submersible, he first found a large seabed plastic pile in the trench of the Xisha Trough in the South China Sea, and collected a wealth of samples. Through sample sharing, researchers from Xiamen University and the Institute of Deep Sea of the Chinese Academy of Sciences conducted a comprehensive and systematic study of the samples collected by jiageng and deep sea warriors. In 2019, the researchers also carried the Beidou research vessel of the Yellow Sea Fisheries Research Institute of the Chinese Academy of Fishery Sciences to collect similar shellfish egg sacs on the Bohai Shared Voyage of the National Foundation of China, and these findings played a key role in studying plastic samples in the South China Sea.
"When I first saw shellfish egg sacs on the surface of plastic, I was deeply shocked, I didn't think that deep-sea plastic waste has become a breeding ground for some marine animals, and then I came into contact with more and more samples, the diversity of species on these plastics is beyond our imagination, there are 11 phyla, 49 species, which makes me eye-open!" Lu Mingxin, a master's student at Xiamen University who participated in the study, said.
Growing upwards like trumpets are the hydra bodies of bowl jellyfish, about a third of which already have the ability to release jellyfish discs, so large plastic piles may become the source of release of local deep-sea mothers; those "plates" with long spines and inverted buckles are Atlantic disc shell shells — they are brachiopods, the dominant species here. There are also cold-water corals, polychaetes, and specialized parasitic flats.
"This is the first time we've seen animals living on plastic up close, and we've been amazed at their diversity." Dr. Bernhard Ruthensteiner of the Bavarian State Museum of Natural History in Bavaria, Germany, who participated in the study, said.
Willow Dark Flowers: There is a "Garden of Eden" at the bottom of the sea
"From shallow to deep seas, the number and diversity of marine life decline dramatically as water depths increase. There is no light here, there is a lack of oxygen, the pressure is also high, and it is very unfriendly to living organisms. "In addition, many marine benthic invertebrates need to live on a harder substrate, but most of the seas only have soft sandy or muddy substrates, which also makes it difficult for them to survive on the deep seabed." ”
But the larvae of some deep seafloor invertebrates are "lucky" to encounter the plastic on the seabed, stick themselves to the surface of the plastic by secreting mucus, and then move on to the next stage of life, gradually growing up.
The newly discovered plastic "oasis" is reminiscent of other known deep-sea ecosystems: deep-sea hydrothermal fluids, cold springs and whale fall. Benthic communities in these habitats are mainly powered by chemical autotrophic bacteria and decomposed cetacean carcasses.
"In contrast, deep-sea plastic biomes appear thin and fragile, and they should rely mainly on plankton carcasses and organic particles that settle from the surface of the sea to drive their operations, which are much less nutritious than hot vents, cold springs and whale fall." Song Xikun told China Science Daily, "Because of this, most of the individuals epiphytic to the surface of plastic are millimeters, which is easy to be ignored by researchers." ”
Woe to the unsure: heaven or a trap?
From the most remote South and North Poles to the deepest Mariana Trench – plastic is everywhere.
Large plastics in the marine environment are very dangerous to some endangered marine life, such as cetaceans, turtles, etc., and in severe cases, they will die by swallowing or being entangled in plastic.
"But the results of this study powerfully impact our traditional perceptions." We have always believed that plastic is harmful to marine life and not beneficial. But it has now been found that, at least for a few organisms, plastic provides them with additional habitat. "The relationship between plastics and biological and ecological environments may be more complex than we expected." ”
Some scientists have also expressed concern. Dr Florian Pohl of Durham University in the United Kingdom, who was not involved in the study, said: "The impact of this change on deep-sea ecosystems is completely unknown, the previous natural habitat may have been damaged by the arrival of plastic waste, native species may also be replaced by plastic waste, and we are not even too late to recognize the ecosystem before plastic arrived here." ”
"It's hard to judge whether this is a good thing or a bad thing." Zhang Xiaodi, a doctoral student at the Institute of Deep Sea Studies of the Chinese Academy of Sciences, who participated in the study, said, "On the one hand, it shows the strong self-regulation ability of marine ecosystems, but on the other hand, more life activities may accelerate the decomposition of plastic waste, which may lead to the formation of more microplastic particles into the biological chain and finally into the human body." ”
For the little life that chooses to make a home on plastic, there is a crisis lurking under the seemingly thriving surface. Atlantic disc shellfish are the dominant taxa here, but researchers have yet to find sexually mature individuals, meaning they are not yet able to reproduce on plastic. Researchers aren't yet sure why, either because the attachment time isn't long enough, or because the hardness of the plastics doesn't allow them to continue to develop to sexual maturity, or because the plastics themselves have unknown hazards to these organisms.
Is the undersea plastic "oasis" a paradise or a trap? There is no definitive answer. "I think whatever is found in plastic, we should call on the public to minimize the use of single-use plastic products and start with ourselves to protect the marine environment." Zhang Xiaodi said. (Li Chenyang)
Related Papers:
https://dx.doi.org/10.1021/acs.estlett.0c00967
Source: China Science Daily