Abstract:

The Ganjiang River is the seventh-largest first-level tributary of the Yangtze River, and knowledge is limited about the river’s macrobenthos assemblages. Here, we carried out a comprehensive assessment of macrobenthos species diversity in the river system, and then identified the potential drivers of the observed community patterns based on combined datasets of available historical records and field investigations from 2016-2017. A total of 330 species have been recorded to date, including 138 from the historical record and an additional 267 from the 2016-2017 investigations. In particular, this river network harbors a high array of mollusk diversity, with 17 gastropods and 31 bivalves endemic to China while 32 molluscs endemic to China were recorded in the 2016-2017 investigations. The dominant species in the Ganjiang River can tolerate pollutants. The density, biomass and richness index of branches of midstream were all higher than those of main stream, branches of the upstream and branches of the downstream. The canonical correspondence analysis (CCA) showed that five environmental factors (substrate, sand-excavating, altitude, turbidity, velocity) and four spatial factors (PCNM1, PCNM11, PCNM12, PCNM15) were the key drivers structuring macrobenthos community variation. The variation partitioning analysis indicated that the environmental factors had a stronger effect on macrobenthos communities than the spatial factors. This study provides useful information to enhance the conservation of benthic biodiversity in the Ganjiang River.

Key words: Ganjiang River, macrobenthos, community structure, biodiversity, canonical correspondence analysis