Corals can filter microplastics out of the water and thus contribute to the fight against marine pollution - albeit at a high price. Scientists at the University of Giessen have come to this conclusion. In saltwater aquariums, they examined four types of coral that are found in the Indo-Pacific. For 18 months they exposed the cnidarians to strong microplastic pollution and were able to observe with the microscope how the corals ingested the approximately 100 micrometer-sized particles. Tissue and skeletal analyzes showed that the animals incorporated up to 84 microplastic particles per cubic centimeter. This happens when the corals filter plankton from the water as food. Foreign substances that they pick up in the process are usually excreted. But sometimes they stay in the coral - like the plastic.
According to study director Jessica Reichert, reef corals around the world can bind up to 20,000 tons of microplastic per year.
That corresponds to about one percent of the microplastics in the reef waters.
With their study, the biologists from Giessen have shown for the first time that living beings can remove microplastics from the environment in the long term.
This service could have fatal consequences for the corals themselves: the stored plastic may damage the stability and resilience of the reefs.
Link to the study: https://doi.org/10.1111/gcb.15920