Multi-marker eDNA metabarcoding reveals multi-taxon biodiversity patterns in oilfield-associated sediments and adjacent seawater of the Yellow River Delta
Coastal oilfield regions are characterized by complex sedimentary environments where petroleum-related inputs, nutrient conditions and metal-associated gradients may jointly influence biological communities. However, biodiversity information from these habitats remains limited, particularly across multiple taxonomic groups. In this study, a multi-marker environmental DNA metabarcoding approach was applied to investigate biodiversity patterns in oilfield-associated sediment and adjacent seawater from the Yellow River Delta, China. Fifteen sediment samples from three oilfield regions, Feiyantan, Gudongquan and Xintan, and three adjacent seawater samples were collected. Four genetic markers were used to characterize sediment bacteria, sediment invertebrates, phytoplankton and fish. After quality filtering and sequence processing, 2,435 bacterial ASVs, 97 invertebrate ASVs, 86 phytoplankton ASVs and 28 fish OTUs were obtained. Bacterial communities showed pronounced spatial variation among oilfield regions, whereas sediment invertebrate communities exhibited weaker but still detectable regional differences. Sediment environmental variables showed clear covariation patterns, particularly among several metal elements. db-RDA and Spearman correlation analyses suggested that bacterial and invertebrate community patterns were associated with multiple environmental gradients, including PHCs, TOC, TN, TP, S2- and metal variables. Overall, this study provides a multi-taxon eDNA biodiversity baseline for coastal oilfield ecosystems and highlights the usefulness of combining eDNA metabarcoding with sediment environmental measurements for ecological monitoring.