Trophic response of fishes to rainfall variability in a temperate estuarine system of Korea: A stable isotope approach

Abstract

To assess the basal resources supporting food webs impacted by rainfalls, we compared stable isotope ratios (δ¹³C and δ¹⁵N) of fish consumers and organic matter sources between up- and down-sites in an estuary between seasons (June and September) and years (2018 and 2019) that showed different patterns of summer monsoon. Our study showed seasonal differences in the δ¹³C and δ¹⁵N values of basal resources and fish consumers in both years. At the up-site, significant differences of δ¹³C values of fish consumers were found between years, resulting from changing rainfall period, thereby causing a shift in food availability from terrigenous organic matter to periphyton. In contrast, at the down-site, the consistent isotopic values of fishes were observed in both years, suggesting that rainfall shift has a negligible impact on resources for fishes. Overall, the annual shift in resources for fishes in the estuary may be controlled by contrasting rainfall events.

Keywords: Climate change; Estuary; Isotopic niches; SIAR mixing model; Stable isotopes; Trophic structure.