Food sources of herbivorous benthic invertebrates using stable isotopes and stomach contents analyses

Abstract

The purpose of this research wasacross to understand the variations of feeding patterns for herbivorous benthic invertebrates (Mesocentrotus nudus and Turbo sazae) different seasons and latitudes along the southern and eastern coasts of the Korean Peninsula using analyses of carbon and nitrogen stable isotopes and stomach contents. Benthic invertebrate and macroalgal samples, and surface seawater were collected from two locations (Tongyeong and Uljin) and during the cold (February-May) and warm seasons (July-August). Muscle tissues of benthic invertebrate, macroalgae and particulate organic matter (POM) were dried for 48h at 60℃, and then analyzed stable isotope ratio using IRMS. Prey items of M. nudus were analyzed using stereomicroscope. 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 only contributed slightly to the diets of the two species. In addition, the proportion of macroalgae in T. cornutus and M. nudus significantly increased during the colder season in Tongyeong. Stomach contents analyses of M. nudus revealed that macroalgae were the primary prey items, making up a substantial volumetric proportion. Both stable isotope and stomach content analyses can strengthen our understanding of the feeding strategies of benthic herbivorous invertebrates and enhance our ability to assess the impact of benthic herbivore grazing on the abundance of benthic macroalgae in Korea.