Marine biodiversity is related to sustainable development and service function of marine ecosystems. The South China Sea (SCS) is an important part of the Indo-Pacific convergence zone, with high biodiversity and abundant marine resources.  

However, species diversity has decreased in the SCS over recent years, and traditional biodiversity monitoring methods have some limitations. 

Recently, Prof. ZHANG Hui from the research team led by Prof. XIAN Weiwei at the Institute of Oceanology of the Chinese Academy of Sciences (IOCAS) conducted a comprehensive study of biodiversity in the SCS by environmental DNA (eDNA) metabarcoding. 

The study was published in Environmental Research on Nov. 11. 

The researchers identified multiple trophic levels from one eDNA sample. Three gene markers were employed, 18S rRNA gene V4 region (18S V4), 18S rRNA gene V9 region (18S V9), and 12S rRNA gene (12S), to amplify three assemblages (phytoplankton, invertebrate, and fish) DNA, respectively, from eDNA samples. 

"We revealed 192 phytoplankton, 104 invertebrate, and 61 fish species from 18S V4, 18S V9, and 12S, respectively," said Prof. ZHANG. Phytoplankton were divided into 19 phyla. Invertebrate belonged to the following two taxa: planktonic protists and metazoans. The fish species belonged to 31 families and 49 genera. 

The three assemblages generally exhibited an increase in species diversity with increasing longitude in the study area in the SCS, said Prof. XIAN. In other words, eDNA abundance reflected the assemblage variations across longitude. 

In addition, the researchers revealed the relationship of the three assemblages and environmental factors. Canonical correspondence analysis showed that four factors, chlorophyll α, depth, salinity, and temperature, were correlated with assemblage structure.

The study was supported by the National Natural Science Foundation of China, the Strategic Priority Research Program of the Chinese Academy of Sciences, and Youth Innovation Promotion Association CAS.