Paradise lost: Microplastic pollution on a remote coral island, Vietnam

Despite microplastic pollution now being ubiquitous in natural environments, there remains several unknowns in terms of which zones may act as microplastics sinks. Coral reefs are the most ecologically diverse marine ecosystem, supporting 25% of all ocean species, and have high socio-economic value, offering ecosystem services such as coastal protection and tourism. However, the average cover of tropical reefs has declined by 50-75% in nearly all global regions over the last 30-40 years due to a range of anthropogenic stressors. There is growing evidence that coral reefs can entrap plastics and that microplastic (>5 mm) pollution threatens coral physiology. However, there is a lack of understanding as to the occurrence, accumulation, spatial distribution and impacts of microplastic pollution on coral ecosystems. It is, therefore, necessary that more research is undertaken within coral reefs to understand microplastic contamination levels and ensure effective mitigation measures are in place.

The islands of Con Dao, Vietnam, are 90 km from the Mekong Delta coast and are a designated national park, with a 14,000 ha marine protected area that conserves endangered wildlife and a diverse range of coral that support hundreds of fish species. Although considered pristine, Con Dao it is influenced by the Mekong River, which is one of the top contributors to marine plastic waste worldwide, posing an increasing risk to this biodiversity hotspot. Understanding the volumes and impacts of microplastic pollution in this area will allow insight into the levels of exposure and risk coral reefs in Southeast Asia, including the highly biodiverse Coral Triangle, have from increasing plastic pollution.Here, the occurrence and spatial distribution of microplastics in water and sand samples from Con Dao is presented. Reef health is also provided through photogrammetry whereby 3D reconstruction of reef sites allows analysis of coral cover and diversity, in addition to structural complexity, which is strongly correlated to reef health indicators including biodiversity, especially within tropical reef ecosystems. Potential sources of microplastics are also discussed through polymer identification by FT-IR analysis.