Consumer‐diet discrimination of δ13C and δ15N: Source‐ and feeding‐oriented patterns based on gut content analysis in a large subtropical river of China,River Research and Applications

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Consumer‐diet discrimination of δ13C and δ15N: Source‐ and feeding‐oriented patterns based on gut content analysis in a large subtropical river of China
River Research and Applications ( IF 2.2 ) Pub Date : 2020-06-16 , DOI: 10.1002/rra.3644
Sai Wang, Bang‐Ke Luo, Ying‐Jun Qin, Lin‐Hui Su, Simon D. Stewart, Tuan‐Tuan Wang, Jin‐Peng Tang, Bai‐Dong He, Jin‐Hua Zhang, Hsing‐Juh Lin, Yang Yang

Understanding the trophic discrimination (∆¹³C and ∆¹⁵N) between consumers and diets in fluvial systems remains difficult because of the variable food sources and complex predator–prey interactions from headwaters to the estuaries. Here, stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotopes in fish and invertebrates from a large subtropical river in southern China were determined to explore trophic discrimination in conjunction with a gut content analysis. The ∆¹³C values showed significant differences (p < .05) among functional feeding groups, with fish, shrimp, and insect scrapers presenting higher ∆¹³C values (1.20 ± 0.23‰ to 1.51 ± 0.31‰) than other groups. The ∆¹⁵N values varied significantly between invertebrates (0.64 ± 0.17‰ of insect collector‐gatherers to 1.63 ± 0.36‰ of shrimp predators) and fish (1.98 ± 0.19‰ of detritivores to 2.71 ± 0.43‰ of crustaceavores) and exhibited an increasing tendency from primary to secondary consumers. A linear regression analysis revealed that the longitudinal changes in ∆¹³C and ∆¹⁵N were closely associated with the δ¹³C of periphyton, the δ¹⁵N of particulate organic matter (POM) in water, and the relative contribution (%) of periphyton and organic detritus to the diet composition of consumers. These results indicated that discrimination factors might not only be influenced by the isotope signatures of basal food sources but also downstream shifts in dominant food items utilized by consumers. In particular, trophic discrimination between periphyton– and detritus–based food chains, such as “epilithic diatoms–shrimp scrapers–crustaceavorous fish” and “POM–bivalves–molluscivorous fish,” displayed regionally specific patterns. When back‐calculating to the diet assimilation and trophic position in subtropical streams and rivers, we suggest using the basin‐scale ∆¹³C value of 0.96 ± 0.26‰ for all consumers and ∆¹⁵N values of 1.07 ± 0.32‰ for invertebrates and 2.38 ± 0.37‰ for fish.

更新日期：2020-06-16

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