Seasonal Variation in Food Web Structure and Fish Community Composition in the East/Japan Sea

Abstract

The aim of this study was to assess the temporal variability in the trophic structure of a fish community and the trophic levels of dominant fish species off the eastern coast of Korea. We analyzed the community composition and the stable carbon and nitrogen isotope ratios (δ 13 C and δ 15 N) for fish species in Hupo coastal waters over four seasons. Fish assemblages were mainly dominated by resident benthic and benthopelagic fish. In contrast, there were low numbers of pelagic fish, including migrating and occasional species, which varied significantly by season. The fish assemblages generally had relatively wide ranges of δ 13 C and δ 15 N (− 21.1 to − 16.3‰ and 10.0 to 14.2‰, respectively), reflecting a clear distinction between resident (mostly benthic or benthopelagic) vs migratory (mostly pelagic) fish. Resident species showed no seasonal differences in their isotopic signatures, whereas pelagic species showed temporal variability in δ 13 C and δ 15 N values. The isotopic niche of fish assemblages showed distinctly different patterns between spring-summer and winter-fall with the seasonal changes in the fish community. These patterns might be associated with seasonal variation in the fish community caused by seasonal changes in environmental conditions (e.g., hydrographic parameters and food availability). Our results can offer baseline information/trophic data for ecosystem models that can be used to evaluate the effects of climate on marine ecosystems.

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

“…Based on the δ 15 N values of herbivores and suspension feeders as benthic and pelagic baselines, respectively, and assuming a trophic fractionation of 3.3 ± 0.26 (McCutchan et al, 2003), our TL estimation denoted that the marine ranching ecosystem is characterized by a trophic length of 3.5, as observed previously in the adjacent restored macroalgal bed (Kang et al, 2008) and natural rocky habitat (Park et al, 2020). The gap in δ 15 N values between primary (herbivores) and tertiary (predatory fish) consumers recorded on average 2.6 to 4.6 (MH site) and 1.8 to 4.6 (PH sie).…”

“…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). The dietary resources of a species within a marine food web can be resolved by the δ 13 C values of its tissues, as the latter contains information on the source (benthic or pelagic) of prey items (Kang et al, 2008;Park et al, 2020). Similary, their δ 15 N values provide an estimation of their position in the food web, increasing with the assimilation of resources at relatively higher trophic levels (TLs; Post, 2002;Caut et al, 2009).…”

Temperature increase drives critical slowing down of fish ecosystems

“…Scientists have realized the importance of deeply capturing the relationship between marine communities and seasonal changes of ocean warming at a finer scale (considering season or shorter time periods). Some studies have also presented apparent seasonal fluctuations of fish abundance and biodiversity in marine ecosystems by assessing and understanding the composition and seasonal changes of the fish assemblage and doing relevant statistical analyses [ 14 – 17 ]. The results suggested that these seasonal variations could derive from the migration and arrival of species and their own seasonal changes of behavior related to the seasonality of temperature patterns.…”

Temperature Increase Drives Critical Slowing Down of Fish Ecosystems

“…Scientists have realized the importance of deeply capturing the relationship between marine communities and seasonal changes of ocean warming at a finer scale (considering season or shorter time periods). Some studies have also presented apparent seasonal fluctuations of fish abundance and biodiversity in marine ecosystems by assessing and understanding the composition and seasonal changes of the fish assemblage and doing relevant statistical analyses [3, 30, 50, 72]. The results suggested that these seasonal variations could derive from the migration and arrival of species and their own seasonal changes of behavior related to the seasonality of temperature patterns.…”