Coral reefs are some of the most unique and biodiverse ecosystems on earth, providing invaluable ecological services and supporting millions of livelihoods worldwide. While they cover less than 1% of the sea floor, coral reefs are home to more than 25% of marine species. However, these vital ecosystems are increasingly threatened by microplastic pollution, which harms their growth, reproduction, and resilience.
The Western Indian Ocean, stretching from East Africa to Mauritius, is an area of great biodiversity, with multiple coral reefs. However, it is also at great risk caused by climate change, pollution, and other anthropogenic activity.
In 2014, an expedition to three of the Mauritian outer islands, Rodrigues, St. Brandon’s Atoll, and Agalega Island investigated chemical contamination in these remote reef systems. Among other studies, microplastic was determined in different corals.
While they may be confused for a plant, or even a rock, corals are living animals of the phylum Cnidaria — same as jellyfish. While most of corals’ nutrition comes from its symbiosis with microscopic algae living in their tissue, they are also equipped with stinging cells and able to actively hunt or engage in filter feeding. As a result of their feeding techniques, they can accumulate microplastic particles either through direct uptake (confused for food items), the particles getting stuck in their skeleton systems, or bioaccumulation if their prey items (zooplankton) have ingested plastic particles earlier.
Microplastics were found in all six coral types sampled, with concentrations averaging 0.78 particles per gram of coral. These included fibers (53%) and fragments (47%), primarily made of polypropylene (PP; 78%) and polyethylene (PET; 18%). This result makes sense because these are some of the most widely used plastic polymers.
Interestingly, microplastic levels were similar across Rodrigues, Agalega, and St. Brandon’s Atoll—remote islands far from major human activities. This uniformity suggests ocean currents, specifically the South Equatorial Current, are distributing plastics over vast distances.
Soft corals, which rely on more active feeding strategies, showed higher microplastic levels than hard corals, which are reliant on symbiosis with zooxanthellate algae.
Coral reefs are biodiversity hotspots and protect coastlines while supporting millions of livelihoods. The ingestion of microplastics by corals can harm their growth, reproduction, and resilience, threatening these fragile ecosystems further impacted by climate change and overfishing.
This study underscores the urgent need for international action to reduce ocean plastic pollution. It highlights the necessity of better monitoring of microplastic pollution and implementing policies targeting plastic waste, especially in remote oceanic regions. Although the data reflects conditions in 2014, it serves as a valuable baseline for tracking changes in microplastic pollution over time.
Addressing this invisible but pervasive threat requires ongoing research and collective action, ensuring the protection of these vital ecosystems for generations to come.
More information:
A new bioinformatic tool, BGC Atlas, was developed by a consortium of bioinformaticians. It identifies and clusters biosynthetic gene clusters from publicly available datasets, offering a centralised database and a web interface for metadata-aware exploration of BGCs and gene cluster families (GCFs).
Jan Velecký is a researcher at the RECETOX center. In the interview, he explains what protein engineering is about, why it is important to study protein solubility, and how machine learning can be crucial for human knowledge.
