Food web structure in the Ulleungdo and Dokdo coasts revealed by stable isotope analysis

Abstract

The objective of this study was to determine the trophic structure of dominant fish and benthic invertebrate species in the Ulleungdo and Dokdo coasts of Korea, based on their stable carbon and nitrogen isotope ratios (δ13C and δ15N). All consumer species and their potential food sources were sampled in May 2021 at the two sampling sites around the Ulleungdo and Dokdo. At the both sites, the whole of consumers had quitely wide ranges of both δ13C and δ15N values (-19.7 to -12.8‰ and 6.2 to 11.8‰ in Ulleungdo and –21.0 to -10.1‰ and 4.3 to 16.9‰ in Dokdo, respectively). However, only for fish species, there were relatively narrow ranges of both δ13C and δ15N values at the both sites (-19.4 to -17.0‰ and 7.6 to 10.9‰ in Ulleungdo and –20.0 to -18.2‰ and 7.4 to 10.8‰ in Dokdo, respectively), suggesting a lower trophic diversity by the narrow isotopic niches. The δ15N values can be generally used to assess the effects of anthropogenic nitrogen inputs on coastal ecosystems. In this regard, the fish species in the two island coasts were considerably lower δ 15N values than those in the Korean coastal waters, suggesting low human activities. These results suggest a unique perspective on trophic relationships between fish species and dietary items in the island coastal ecosystem.