Stable isotope analysis of food sources sustaining the subtidal food web of the Yellow River Estuary

Abstract Estuarine food webs can be supported by local benthic or pelagic primary producers and by the import of organic matter. Until now, studies precisely quantifying the main energy sources in estuarine food webs have been limited for diverse species. The main pathway by which primary nutrients and energy are transported is not explicit and impedes conservation and restoration of estuarine ecosystems in Marine Protected Areas (MPAs). In this study, carbon and nitrogen stable isotopes were measured, to assess the primary food sources for consumers in the subtidal zone of the Yellow River Estuary. More than half of the detected consumers showed a balanced diet, with no significant feeding preferences. The remaining consumers mainly relied on microphytobenthos (MPB) and Cordgrass ( Spartina ). MPB contributions ranged from 31% to 38% for fishes and from 24% to 33% for invertebrates, while the contribution of Spartina ranged from 30% to 43% for fishes and from 24% to 38% for invertebrates, respectively. MPB was regarded as the primary autochthonous food source, while Spartina was regarded as the primary allochthonous source. Consumers showed a low reliance on food sources originating from the Yellow River, with diets conforming more to a marine based pattern. This study provides the first detailed investigation of the contribution of food sources in the subtidal zone of the Yellow River Estuary. The results of this study enhance our understanding of energy pathways in estuarine ecosystems, in addition to providing data to inform the conservation and restoration of coastal ecosystems.