Nekton food web structure and dynamics in the Southern Sea of Korea

Abstract

The global environmental changes have altered the major environmental drivers in the marine ecosystems, leading to reshaping the food web structures. This research addressed the energy flow in the estuarine, coastal and offshore continental shelf food webs and how their linkage to the environmental gradients over space and time. This research employed stable isotopes and fatty acid analysis to quantify the relative contribution of basal resources and their pathways to the motile nektonic consumers. Studies were carried out in a low turbidity coastal embayment and the offshore continental shelf ecosystem in the Southern Sea of Korea. This dissertation is composed of three separate studies. The first study found that fish food web in low turbidity and high productivity coastal ecosystems are mostly fueled by phytoplankton which contrasts to the existing consensus of high importance of detritus-based organic matter in estuarine and nearshore food webs. In the second study, a combined approach by stable isotopes and fatty acid composition showed that in phytoplankton-based coastal ecosystems, the fish food webs demonstrate limited seasonal variation due to trophic redundancy under sufficient primary production. The third study suggested a reduction in benthic-pelagic coupling during stratified water condition shifts the trophic dynamics of pelagic and bentopelagic fish in offshore continental shelf ecosystems. Together the three studies highlighted the food web structures in the different compartments of the marine ecosystem in the Southern Sea of Korea. The findings of this study can provide empirical information for the predictive ecosystem modeling and develop strategies for sustainable utilization and management of marine ecosystems.