According to a study from the Justus Liebig University in Gießen (JLU), reef-forming corals incorporate small plastic particles permanently into their calcareous skeleton and contribute in this way to cleaning the seawater of microplastic. For the study, Dr. Jessica Reichert and her team examined four types of coral that live in the Indopacific. They simulated a heavy microplastic pollution and subsequently analysed skeletons and tissue of the corals.

 

Dr. Jessica Reichert, who heads the study, and her team estimate that the studied types of coral in reefs could bind worldwide up to 20,000 tons of microplastic a year, which is around 1 percent of the microplastic in the reef water. "Corals are the first organisms to be discovered as a living sink for microplastic in the sea. Our study puts coral reefs in a new light. They not only help to maintain the ecological equilibrium of the oceans, but also serve as a long-term storage system for microplastics," says the coral researcher. For the study, Reichert and her team simulated heavy microplastic contamination in seawater aquariums over a period of more than 18 months. Through a microscope, they observed live how the corals ingest the small, approx. 100 micrometre particles into their bodies. The plastic particles get into  the animals' organism together with seawater. Corals normally live on plankton that they filter from the water with special cells. In this process, other small particles are also ingested. "Normally, the coral excretes such inedible particles again," says Reichert. "Occasionally, however, something goes wrong with this self-cleaning process. The coral chokes, so to speak, and the particle remains in the body." How many microplastic particles get into the bodies of the sea creatures through this process was shown by tissue and skeleton analyses of 54 corals. It was found that the animals stored up to 84 microplastic particles per cubic centimetre – predominantly in the skeleton, but also in the tissue. One of the studied corals, as Reichert reports, took up as much as 600 microplastic particles and, in the process, doubled its body size from five to ten centimetres. What long-term consequences for the corals and reef systems are connected with the storage of microplastic is still unclear. An earlier study from the Gießen team together with an Australian research group had shown that some coral species when subjected to microplastics grow more slowly or can become ill. Reichert also suspects that the ingestion of microplastic could have a long-term effect on the stability and level of resistance of reefs. Microplastic would then be an additional threat to the eco systems already endangered by climate change.

 
Further information: download the study „Reef-building corals act as long-term sink for microplastic“

 

Sources:

• Informationsdienst Wissenschaft idw-online.de (Nov. 30, 2021)
• chemie.de (Dec. 2, 2021)
• Photo: © unsplash.com, Claudio Schwarz