Plastisphere: a new ecosystem was born in a littered ocean

Plastisphere: a new ecosystem was born in a littered ocean
Plastisphere: a new ecosystem was born in a littered ocean
12 August 2021, 10:03SciencePhoto: Rebecca Ricks
Environmentalists are studying the properties of the plastisphere, a synthetic ecosystem that has developed in the oceans with the appearance of a huge amount of plastic waste.

Its inhabitants are organisms that have adapted to this environment, from animals floating on plastic bottles in the ocean to bacteria feeding on plastic.

The main source of pollution in the oceans is plastic bottles, with an estimated 1 million bottles entering the world's waters every minute. As a rule, these are bottles made of polyethylene terephthalate, or PET. Last month, scientists identified two ocean-dwelling bacteria that eat PET bottles, Thioclava sp. BHET1 and Bacillus sp. BHET2. This discovery is further evidence that ocean plastic has created its own unique environment in which new organisms emerge. The Guardian talks about what is hidden behind the term "plastisphere", which appeared in ecology less than ten years ago, but promises to remain forever.

The word "plastisphere" was coined by Linda Amaral-Zettler, a marine microbiologist at the Royal Netherlands Institute for Marine Research. According to the scientist, she tried to come up with an understandable term for biofilm on plastic. A biofilm is the term for a set of microorganisms located on a surface, the cells of which are attached to each other. This is how the word "plastisphere" appeared in a study published in 2013 by the journal Environmental Science & Technology. According to Amaral-Zettler herself, despite the novelty of the word, the concept behind it is much older - the plastisphere has existed since plastic appeared. The plasticized marine environment is an ecosystem like coral reefs or Siberian taiga. Its most famous fragment is the Great Pacific Garbage Patch, an accumulation of anthropogenic garbage about the size of two France. But there are no more places on Earth without plastic.

If in the 2013 work, of which Amaral-Zettler was one of the authors, the plastisphere meant only a group of organisms that colonize plastic, such as bacteria and fungi, then since then the content of the term has become noticeably wider. Now the inhabitants of the plastisphere are, for example, such large organisms as crabs and jellyfish, which travel across the ocean using plastic as a means of transportation. The understanding of the plastisphere has also evolved: this ecosystem is already clear, somewhat complex. It contains organisms that live by photosynthesis, there are predators and prey, there are symbionts and parasites - that is, according to Amaral-Zettler, "the full range of possible interactions, as in other ecosystems."

The plastisphere differs from all other ecosystems in that it did not evolve over millions of years, but appeared simultaneously and thanks to the efforts of people. However, despite the artificiality of the origin of the environment itself, all its inhabitants are quite natural. In addition, they have excellent developmental opportunities: unlike most natural materials, plastic is highly durable and resistant, allowing attached organisms to grow and spread over a huge area.

One recent study has demonstrated an interesting feature of the plastisphere: certain colors of the plastic affect the diversity of the microbes that colonize them. Thus, communities on blue microplastics had a richer diversity than communities on yellow or transparent plastic. The plastisphere is potentially dangerous: organisms colonizing plastic can travel all over the world, and among them there are harmful ones. In the same 2013 study, vibrios were described containing pathogens that, among other things, cause gastroenteritis. Some of the plastic that gets into the water sinks, while the other floats on the surface, becoming the habitat of all kinds of microbes. When plastics are submerged in water, they attract carbon, iron, nitrogen and phosphorus, which in turn attracts microorganisms.

Potential pathogens are one of the issues of greatest interest to researchers in the plastisphere. The second is the ability of some microbes to biodegrade hydrocarbons, that is, to devour plastic. The latter ability is not, in general, unique. Five years ago, Japanese scientists discovered Ideonella sakaiensis in a landfill, a bacteria that developed an enzyme that allowed them to eat plastic. However, as shown by another study, the inhabitants of the plastisphere have a richer genome - probably, this helped them to adapt to the "surface lifestyle." At the same time, they are by no means mutants: although plastics are a relatively new material, it is made mainly from oil components. So the bacteria had plenty of time to develop degradation mechanisms. Perhaps, in the future, bacteria, if they do not completely eat up the plastisphere, will at least tell us how to solve the problem of plastic waste.

In any case, scientists will have to carefully study the microbiome of the plastisphere, which, like the microbiome of the gastrointestinal tract for humans, is extremely important for the health of the planet. It is already quite clear that, once it has appeared, the plastic ecosystem will remain with us forever.

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