Stable Isotope Variations in Particulate Organic Matter and a Planktivorous Fish in the Yangtze River

ABSTRACT

Temporal and spatial changes in δ¹³C and δ¹⁵N of particulate organic matter (POM) and Hemiculter leucisculus were studied in the Yangtze River of China. Isotopic signatures of POM showed seasonal variations, which was assumed to be associated with allochthonous organic input and autochthonous phytoplankton growth. δ¹³C of H. leucisculus was 1.1% higher than that of POM, which suggested that the food source of H. leucisculus was mostly from the POM. A mass balance model indicated the trophic position of H. leucisculus in the food web of Yangtze River was estimated to be 2.0–2.1, indicating that this fish mainly feeds on planktonic organic matter, which agreed with previous gut content analysis.