Abstract:Bioturbation of macroinvertebrate is one of the key factors in maintaining the nutrient cycling in freshwater ecosystems. Currently,the understanding of the similarities and differences in the bioturbation effects between benthic macroinvertebrate communities and single species was still very limited. This study aims to explore the differences in bioturbation effects caused by single species and communities,as well as the effects on the distribution characteristics of the biogenic element such as organic carbon and nutrients at the sediment-water interface in freshwater systems. We selected five typical benthic species (Unio douglasiae,Bellamya aeruginosa,Corbicula fluminea,Neocaridina denticulata sinensis and Limnodrilus hoffmeisteri) for laboratory culture experiments. Seven microcosmos were established to culture benthic macroinvertebrate populations (signal species group) and their communities (community group). Nutrients including ammonia nitrogen (NH3-N),nitrite (NO2--N),nitrate (NO3--N),dissolved total phosphorus (DTP),and dissolved organic carbon (DOC) in both the sediment (upper layer and bottom layer) and overlying water,influenced by bioturbation,were measured at the beginning and seventh day. Besides,the changes of the tested variables induced by per unit biomass for each group were calculated. The results indicated that the bioturbation by single species groups led to a decrease of NH3-N in sediment (P < 0.05) and an increase of NO3--N content both in sediment and overlaying water (P < 0.05). In contrast,the bioturbation of the community group promoted an increase in NH3-N (P < 0.05) and induced the NO3--N deposition from the overlying water into the sediment. The community group significantly increased the DTP content in the overlying water (P < 0.05),but this phenomenon was not observed in signal species groups. The independent bioturbation of single species groups all promoted a decrease in DOC content in the overlying water (P < 0.05). Limnodrilus hoffmeisteri was the only species that resulted in a decrease in the DOC content of sediments (P < 0.05). In contrast,the DOC concentration within the community group remained unchanged (P > 0.05),due to intermediate interactions among the benthic macroinvertebrates. On a per-unit-biomass basis,the community group's effects were less pronounced than those of the single species groups. The bioturbation effect per unit biomass of Limnodrilus hoffmeisteri had the most significant impact on the changes in the concentrations of C,N,and P in the overlying water and sediment. However,its bioturbation effect was suppressed in the community condition,meaning that the species with a high bioturbation intensity per unit biomass were more likely to be suppressed in the community.