Trophic niche and food resource for herbivorous benthic invertebrates using stable isotope

Abstract

This study aimed to identify seasonal and latitudinal differences in benthic food web structures along with southern and eastern coast of Korean peninsular using carbon and nitrogen stable isotope analyses. Benthic invertebrate and macroalgal samples, and sufrace seawater sample were collected from two regions (Tongyeong and Uljin) during the cold (May) and warm season (July-August). Muscle tissues of benthic invertevbrate, plant tissue and particulate organic matter (POM) which was filtered from seawater were dried for 48h at 60℃, and then analyzed stable isotope ratio using IRMS. Common herbivorous benthic invertebrates in Uljin were Turbo cornutus and Mesocentrutus nudus, while T. cornutus, Hemicentrotus pulcherrimus, and M. nudus were the abundant herbivores in Tongyeong. In both regions, benthic invertebrates showed much higher stable isotope values (both carbon and nitrogen) than macroalgae and/or POM, indicating that the macroalgae and POM were the important food sources for herbivorous benthic invertebrates. According to isotopic mixing model, the proportion of macroalgae in the diet of T. cornutus and M. nudus was higher in the warm than in the cold seasons, and higher in Uljin than in Tongyeong. While POM were not direct food sources for T. cornutus and M. nudus, but contributed slightly to the diets of the two species. Further studies such as gut contents analyses of benthic herbivorous invertebrates combined with the stable isotope analysis can enhance our abilities to evaluate impact of grazing by benthic herbivores on benthic macroalgal abundance in Korean waters.