Responses of macroinvertebrates and local environment to short-term commercial sand dredging practices in a flood-plain lake

Highlights: • Effects of sand dredging on inland freshwater ecosystems have rarely been studied. • Short-term sand dredging activity resulted in changes to water depth, transparency, sediment particle size, and lakebed fauna. • Taxa richness, abundance and biomass were enhanced in area adjacent to dredging result of changes in physical parameters. • Alterations to the benthic community were caused by direct removal of sediment and indirect changes to physical conditions. In parts of the developing world, the expansion of industrial sand mining activities has led to serious environmental concerns. However, current understanding of the effects of this activity on an inland water ecosystem remains limited. Herein, we choose the "most affected" lake in China (Dongting Lake), to assess short-term (1 year) effects of sand dredging on key environmental parameters and on the structure of the macroinvertebrate assemblage. Within the dredged area we observed increases in water depth (on average 2.17 m), turbidity and changes in sediment composition (e.g., increase in % medium sand, and a decrease in % clay). In addition, dredging was associated with a 50 % reduction in taxa richness, Simpson and Shannon-Wiener indices, and a 72 and 99 % reduction in abundance and biomass, respectively. Indirect effects were also observed in the zone surrounding the extraction sites (ca. 500 m), most likely as a result of the dredging processes (e.g., sediment screening and overspill) and water flow. No such effects were observed at a nearby reference site. The direct removal of sediment and indirect alteration of physical conditions (e.g., water depth, turbidity and sediment composition) appear to be the most likely cause of variations in the benthic community. Implications of our findings for the planning, management and monitoring of sand dredging in inland waters are discussed.