Cross-ocean patterns and processes in fish biodiversity on coral reefs through the lens of eDNA metabarcoding

Increasing speed and magnitude of global change threaten the world's biodiversity and particularly coral reef fishes. A better understanding of large-scale patterns and processes on coral reefs is essential to prevent fish biodiversity decline but it requires new monitoring approaches. Here, we use environmental DNA metabarcoding to reconstruct well-known patterns of fish biodiversity on coral reefs and uncover hidden patterns on these highly diverse and threatened ecosystems. We analysed 226 environmental DNA (eDNA) seawater samples from 100 stations in five tropical regions (Caribbean, Central and Southwest Pacific, Coral Triangle and Western Indian Ocean) and compared those to 2047 underwater visual censuses from the Reef Life Survey in 1224 stations. Environmental DNA reveals a higher (16%) fish biodiversity, with 2650 taxa, and 25% more families than underwater visual surveys. By identifying more pelagic, reef-associated and crypto-benthic species, eDNA offers a fresh view on assembly rules across spatial scales. Nevertheless, the reef life survey identified more species than eDNA in 47 shared families, which can be due to incomplete sequence assignment, possibly combined with incomplete detection in the environment, for some species. Combining eDNA metabarcoding and extensive visual census offers novel insights on the spatial organization of the richest marine ecosystems

ORGANIC MATTER AND NUTRIENT PROFILE OF THE TWO-CURRENT-REGULATED-ZONE IN THE SOUTHWESTERN SUMATRAN WATERS (SSW)

The Indian Ocean is influenced by monsoon systems which alter the ocean’s physical and chemical properties. Specifically, the southwestern Sumatran waters in the eastern Indian Ocean are considered a dual current regulated zone i.e. affected by South Equatorial Counter Current (SECC) and South Java Current (SJC). This area is considered as having an important role in the transfer of organic matter or the biological pump. However, the information about this area is minimal, especially in terms of organic matter and nutrient profile. This study will update the recent information about the area, including the profile of particulate organic matter (POM), macro-nutrients, total suspended solids (TSS), macromolecule-degradingbacteria, and soft bottom macrobenthic organisms sampled from 26 stations in both the SECC-regulated zone and the SJC-regulated zone. The physical profile is typical of tropical watersand both zones have a distinct profile of organic matter and nutrients. The particulate organic carbon (POC), particulate organic nitrogen (PON), and TSS of the SECC-regulated zone can be considered higher than those of the SJC-regulated zone. This region is categorized as mesotrophic waters, especially from the surface up to 100 m. The production of nutrients and organic matter in the water column in this area contribute significantly to the abundance of heterotrophic bacteria and benthic organisms

Circumglobal distribution of fish environmental DNA in coral reefs

DNAQUA International Conference : international Conference on the Use of DNA for Water Biomonitoring , [En ligne], , -Coral reefs host the highest fish diversity on Earth despite covering less than 0.1% of theocean’s seafloor. At the same time they are also extremely threatened. Data synthesesover decades of surveys estimate the total number of coral reef fishes to vary from 2,400 to8,000 species distributed among roughly 100 families. But this diversity remains largelyunknown