Trophic dynamics of macroinvertebrate communities of a subtropical river in China

Abstract

This study was the first attempt to resolve both spatial and temporal patterns of macroinvertebrate trophic dynamics in a Chinese subtropical river continuum, the Shengli River, from 1st to 4th order. Gut content analysis was adopted to assess the trophic basis and consumption rates of communities. Furthermore, annual energy flow food webs were constructed. Trophic basis analyses showed that 34–79% of the diet of macrozoobenthos in the Shengli River and its tributaries was amorphous detritus. Leaf litter was the second most important food source, followed by animal material. Filamentous algae, diatoms, and fungi served only as subsidies, contributing no more than 5% to total consumption. The macroinvertebrates in 1st and 3rd order streams appeared to show seasonal consumption patterns of different food types, while the communities in 2nd and 4th order streams had the same diet composition throughout the year. Total consumption rates of the communities increased from 1st to 3rd order streams, and declined in 4th order streams. The energy flow food web of 1st order streams was simpler than those of higher‐order streams. With increasing stream order, the food webs increased in complexity until 3rd order, and became simpler again in 4th order streams.