The plastic waste floating in the sea has become a new habitat for some organisms: bacteria, viruses, fungi and algae form thriving biofilms on the waste particles. DNA analyzes of colonized plastic parts from the two large garbage patches in the North Pacific and North Atlantic now show how the inhabitants of the plastisphere have adapted to their artificial environment. They reveal specific genetic differences between plastic inhabitants and plankton microbes.
Millions of tons of plastic end up in the oceans every year through rivers, air and beaches. There they spread to the most remote areas, are ground up into microplastics and deposited on the seabed. Other pieces of plastic form huge garbage patches in the large currents of the Pacific and Atlantic. Plastic pollution has long been endangering many animals, damaging ecosystems and also our health. But there are organisms that have adapted: for them, the floating plastic carpets and plastic particles have become a new habitat – the plastisphere.
Expedition to the garbage patches of the oceans
But how do the bacteria, viruses, fungi and algae that live in plastic adapt to this new habitat? “The plastisphere has been well studied taxonomically. What is less known, however, are the functional strategies that enable the microorganisms in the biofilm to survive under the extreme conditions of a nutrient-poor environment and high UV pollution on the surface of the open oceans,” explains co-author Mechthild Schmitt-Jansen from the Helmholtz Center for Environmental Research (UFZ) in Leipzig.
To investigate this, two research teams visited the two large plastic waste whirlpools in the North Atlantic and North Pacific in 2019 and collected samples of the macroplastic floating around there. They then analyzed these samples in the laboratory for the DNA present in them. The focus of these analyzes was on the functional genes of the genetic material present on the plastic. “Functional genes contain genetic information that allows microbes to, for example, produce proteins, control metabolic processes, build cell structures or regulate signaling processes in the cell,” explains co-author Erik Borchert from the GEOMAR Helmholtz Center for Ocean Research Kiel.
Larger genomes and more genes
The result: “Our data reveal a characteristic metagenome of the plastisphere with similar features in both seas,” report the researchers. The bacterial biofilms on the floating plastic parts therefore differ significantly in their genetic structure and function from those of the microorganisms floating freely in the sea. “The microorganisms in the biofilm have more gene copies in order to effectively absorb nutrients, use and break down carbon and ward off UV radiation through effective mechanisms or quickly repair damage to the genome,” reports lead author Stefan Lips from the UFZ.
The analyzes also showed that the genomes of the microbial plastic inhabitants are, on average, significantly larger than those of normal sea plankton. “While planktonic microbes have streamlined their genomes to minimize the costs of their growth, the plastisphere shows less evidence of such adaptation to nutrient-poor conditions,” the researchers explain. “On the contrary: the plastisphere has larger, nitrogen-rich genomes with more non-essential genes.”
No need to save
Lips and his colleagues see the reason for this in the better availability of nutrients on the plastic particles: in the biofilms, different types of microbes provide each other with building blocks for their metabolism. The chlorophyll concentrations are also higher in the biofilms than in plankton, and the plastic inhabitants can use alternative energy sources such as anoxygenic photosynthesis, in which no oxygen is produced. “This suggests that the microbes of the plastisphere have the potential to produce more biomass relative to the surrounding plankton,” explains Schmitt-Jansen. “As a result, eutrophic niches are formed in the nutrient-poor desert of the open oceans.”
Taken together, the results show that the microbial inhabitants of marine plastic have adapted to their artificially created habitat in several ways. This is good for these microorganisms, but not necessarily for the oceans: “This is not a good sign for the oceans because only their original, natural state is considered healthy – and any deviation from this is considered a deterioration,” says Lips. Whether and how plastic growth influences the sensitive geochemical balance of marine ecosystems now needs to be further researched.
Source: Helmholtz Center for Environmental Research – UFZ; Specialist article: Environmental Pollution, doi: 10.1016/j.envpol.2026.127830