Lateral carbon export of macroalgae and seagrass from diverse habitats contributes particulate organic carbon in the deep sea of the Northern South China Sea.

Our study explored the lateral export of macroalgae and seagrass to the deep sea of the Northern South China Sea (NSCS). Particulate organic carbon (POC) collected from a depth of 500 m off southwestern Taiwan (station T) and Dongsha Atoll (station K) underwent environmental DNA (eDNA) and stable isotope assays. Metabarcoding using 18S V9 rDNA revealed lateral export of macrophyte detritus in NSCS. At station K, seagrass detritus predominated, while at station T, macroalgae-derived detritus was dominant. The consistency in the stable carbon isotope signature between POC and macrophytes indicates that stable carbon is an ideal bio-indicator for tracking macrophyte detritus destination and transformation after it has been laterally exported. Based on robust scientific methods, these findings provide valuable insights into the lateral export of macrophyte detritus to the deep sea in POC, influenced by habitat species, and shaped by distinct oceanographic physics around NSCS.