Identifying patterns in the multitrophic community and food-web structure of a low-turbidity temperate estuarine bay

Abstract

Food web dynamics outline the ecosystem processes that regulate community structure. Challenges in the approaches used to capture topological descriptions of food webs arise due to the difficulties in collecting extensive empirical data with temporal and spatial variations in community structure and predator–prey interactions. Here, we use a Kohonen self-organizing map algorithm (as a measure of community pattern) and stable isotope-mixing models (as a measure of trophic interaction) to identify food web patterns across a low-turbidity water channel of a temperate estuarine-coastal continuum. We find a spatial difference in the patterns of community compositions between the estuarine and deep-bay channels and a seasonal difference in the plankton pattern but less in the macrobenthos and nekton communities. Dietary mixing models of co-occurring dominant taxa reveal site-specific but unchanging food web topologies and the prominent role of phytoplankton in the trophic base of pelagic and prevalent-detrital benthic pathways. Our approach provides realistic frameworks for linking key nodes from producers to predators in trophic networks.

Phytoplankton Fuel Fish Food Webs in a Low-Turbidity Temperate Coastal Embayment: A Stable Isotope Approach

“…The difference in trophic enrichment between estuarine and coastal nekton highlights the biological transport of coastal OM to the estuary. Notable seasonal patterns have been reported in primary producers and lower TL consumers from GYB (Kang et al, 2020). Therefore, the apparent consistency in the nekton species composition, stable isotope values, and trophic contribution of OM sources indicates the resilience of fish food webs in GYB under changing environments.…”

“…However, the mobility of nekton adds more dimensions to dynamics of higher trophic level consumers like fish, which are limited within the lower trophic level macroinvertebrates. Although we have reported the OM flow to dominant fish taxa through primary consumers in order to explain the patterns of multitrophic (plankton, primary and secondary consumers) community structures (Kang et al, 2020), the scope for incorporating community wide approach for nekton was limited. In this study, we quantified and elaborately evaluated the OM sources supporting nekton food web by incorporating intergroup variability and mobility of consumers, and further established the findings in multitrophic study (Kang et al, 2020).…”

Biochemical Composition of Seston Reflecting the Physiological Status and Community Composition of Phytoplankton in a Temperate Coastal Embayment of Korea

“…Because of the mixing of freshwater and seawater, estuaries are characterized by pronounced gradients of physical, biogeochemical, and biological processes [2]. Spatiotemporal variabilities in these processes strongly influence the biological community characteristics of the estuarine-marine continuum [3][4][5]. Seston is composed of suspended living and dead material, and plays a vital role in the biogeochemical cycling of materials in estuarine and marine ecosystems [6].…”

“…The seasonal variability in phytoplankton community composition and primary production is tightly coupled to high input of nutrients delivered by freshwater [24,29,30]. Furthermore, recent evidence demonstrates that in situ primary production, principally by phytoplankton, serves as the prevalent contributor of SPM and POM in this embayment system, thus providing a major trophic base to the benthic and pelagic food web [5,26,31]. For this reason, Gwangyang Bay provides an excellent test-bed system to examine the spatiotemporal variations in the biochemical composition of seston, which may provide insight into the major biogeochemical processes linked to the high biological activity (i.e., phytoplankton biomass and primary production) observed in the phytoplankton-based coastal ecosystem.…”

Food Web Trophic Structure at Marine Ranch Sites off the East Coast of Korea

“…The GPO may move considerable distances on foraging paths from their dens, so the midden contents might not reflect their complete diets (Hartwick et al, 1984;Scheel and Bisson, 2012). More importantly, their diet compositions may seldom capture topological descriptions of food webs to characterize their trophic niche (Kang et al, 2020). Alternatively, carbon and nitrogen stable isotope analyses (referred to here as δ 13 C and δ 15 N values, respectively) have been applied successfully to the identification of diets, feeding habits, and trophic ecology of cephalopods (Cherel et al, 2009;Merten et al, 2017;Murphy et al, 2020).…”