Researchers from Japan and Thailand have made a groundbreaking discovery regarding microplastics in coral. They found that all three parts of the coral anatomy—surface mucus, tissue, and skeleton—contain microplastics. This significant finding was made possible thanks to a new microplastic detection technique developed by the team and applied to coral for the first time.
These findings may also shed light on the ‘missing plastic problem’ that has puzzled scientists, where about 70% of the plastic litter that has entered the oceans cannot be found. The team hypothesizes that coral may be acting as a ‘sink’ for microplastics by absorbing it from the oceans.
Humanity’s reliance on plastics has undeniably brought convenience to our lives but has also caused severe damage to our ecosystem. In the oceans alone, an estimated 4.8–12.7 million tons of plastics flow into the marine environment annually. These findings underscore the urgent need to address the pervasive issue of plastic pollution for the health of our planet.
“In Southeast Asia, plastic pollution has become a significant issue. Collectively, nearly 10 million tons of plastic waste are dumped annually, equivalent to 1/3 of the world’s total,” explains Assistant Professor Suppakarn Jandang from Kyushu University‘s Research Institute for Applied Mechanics (RIAM) and first author of the study. “Some of this plastic is discharged into the ocean, where it degrades into microplastics.”
In 2022, RIAM joined forces with Thailand’s prestigious Chulalongkorn University to establish the Center for Ocean Plastic Studies, a pioneering initiative aimed at tackling the pressing issue of plastic pollution in Southeast Asia. Spearheaded by the esteemed Professor Atsuhiko Isobe, the international institute is set to make waves with its groundbreaking research.
Focusing on the coastal region of Si Chang Island in the Gulf of Thailand, the research team delved into the profound impact of microplastics on local coral reefs. Renowned for its pristine reef flats and significance in anthropological studies, Si Chang Island provided a captivating backdrop for the team’s vital field work.
“Coral has three main anatomical parts: the surface mucus, the outside of the coral body; the tissue, which is the inner parts of the coral; and the skeleton, the hard deposits of calcium carbonate they produce. Our first step was to develop a way to extract and identify microplastics from our coral samples,” continues Jandang. “We put our samples through a series of simple chemical washes designed to break apart each anatomical layer. After each subsequent layer was dissolved, we would filter out the content and then work on the next layer.”
The team collected and studied 27 coral samples across four species and found 174 microplastic particles, with most ranging from 101–200 μm in size. The microplastics were distributed with 38% on the surface mucus, 25% in the tissue, and 37% in the skeleton.
The most prevalent types of microplastics found were nylon, polyacetylene, and polyethylene terephthalate (PET), accounting for 20.11%, 14.37%, and 9.77% of the identified samples, respectively. These findings suggest that coral may act as a marine plastic ‘sink,’ sequestering plastic waste from the ocean.
“The ‘missing plastic problem’ has been troubling scientists who track marine plastic waste, but this evidence suggests that corals could account for that missing plastic,” says Jandang. “Since coral skeletons remain intact after they die, these deposited microplastics can potentially be preserved for hundreds of years. Similar to mosquitos in amber.”
Further study is needed to fully comprehend the implications of these findings on coral reefs and the global ecosystem. It is imperative that we delve deeper into this matter to gain a comprehensive understanding of its far-reaching impact.
“The corals that we studied this time are distributed all around the world. To get a more accurate picture of the situation, we must conduct extensive studies globally across an array of coral species,” concludes Isobe. “We also do not know the health effects of microplastics on coral and the larger reef community. There is still much to be done to accurately evaluate the impact of microplastics on our ecosystem.”
Journal reference:
- Suppakarn Jandang, María Belén Alfonso, Haruka Nakano, Nopphawit Phinchan, Udomsak Darumas, Voranop Viyakarn, Suchana Chavanich, Atsuhiko Isobe. Possible sink of missing ocean plastic: Accumulation patterns in reef-building corals in the Gulf of Thailand. Science of The Total Environment, 2024; DOI: 10.1016/j.scitotenv.2024.176210