Distribution of Eukaryotic Environmental DNA in Water and Sediment from Offshore Petroleum Platforms in the Gulf of Thailand

Biomonitoring and environmental impact assessment of marine ecosystems are important for the effective management of petroleum platform activity. Eukaryote biodiversity in water and sediment near petroleum platforms in the Gulf of Thailand was surveyed using environmental DNA (eDNA) based on 18S ribosomal DNA variable region 4 (18S rDNA-V4), the full-length 18S rDNA gene (18S rDNA-FL), and cytochrome c oxidase subunit 1 (COI). Water and sediment samples were collected from three platforms. The water sample was also collected from a reference site located farther south, away from the platforms. Both 18S rDNA markers outperformed COI. A total of 1144 and 889 species were found in water and sediment when analyzed by 18S rDNA-V4, and 519 species were found in sediment when analyzed by 18S rDNA-FL. Only 99 species were found in water samples when analyzed by COI. Alpha-diversity (Shannon and Simpson Evenness) indices were significantly different in water (p < 0.05), but not in sediment (p > 0.05). Beta-diversity (PCoA and NDMS) revealed significant species components between different petroleum platforms (p < 0.01). Species distribution revealed biological connectivity between eukaryotes from different platforms suggesting the importance of platforms on ecological impacts. This study also illustrates the possible application of eDNA for monitoring ecological toxicity around petroleum platforms.