Isotopic identification of trophic structure in a Hupo marine ranching ecosystem off the southwestern coast of East Sea

Abstract

In order to enhance fisheries resources by creating hard bottom ecosystem on the sandy habitat in coastal zone, artificial reefs are deployed and juvenile fish are released in marine ranching area. The present study firstly examined trophic structure in the Hupo marine ranching ecosystem of the southwestern coast of the East Sea. Samplings for colonized biota and potential sources of organic matter were performed at artificial reef (AR), natural rocky reef (NR), and sandy-mud bottom (NS, control site) habitats in July and November 2010. Although little different isotope values of organic sources between sites and seasons was appeared, significantly less negative δ13C of benthic algae than that of phytoplankton were shown. No spatial and seasonal difference of isotopic signature of consumers (divided by cluster analysis) was found between NR and AR ecosystem in July and November. Besides more negative δ13C values of consumers at AR habitats compared to those at NS habitat were presented. Thus, deployment of artificial reefs made the trophic structure of sandy bottom ecosystem alike that of rocky bottom ecosystem though diversify trophic base. Same trophic niche between released and wild starry flounders suggested that successful settlement of released individuals. Further studies directed to long-term monitoring on seasonal and interannual variations of trophic structure by the effects of the creations of new macroalgal habitats on fisheries yield.