Deposit-feeding aquatic oligochaete worms are abundant and widely distributed benthic animals in lakes that affect the nutrient cycling between sediments and the water and thus the water quality. This effect can be density-dependent and affected by the presence of filter-feeding bivalves, which can modulate the worms’ impact. We conducted a mesocosm experiment with high, medium, and low densities of the tubificid worms Limnodrilus hoffmeisteri (Oligocheata, Tubificida, and Naididae) in the presence of the filter-feeding bivalve Hyriopsis cumingii. In the low-density treatment, the concentrations of nitrate nitrogen (NO3−-N), ammonium nitrogen (NH4+-N), and organic suspended solids (OSSs) increased moderately compared with the control. In the medium- and high-density treatments, there were also increases in total nitrogen (TN), total phosphorus (TP), soluble reactive phosphorus (SRP), total suspended solid (TSS) and inorganic suspended solid (ISS) concentrations. Moreover, the biomass of phytoplankton (Chl a), the light attenuation coefficients, and the abundance of both cladoceran and rotifer zooplankton rose with increasing worm densities. Water quality deteriorated in both the medium and high worm density treatments, likely due to increased nutrient leading to an increase in the biomass of phytoplankton in our mesocosms, even though plankton-consuming bivalves were present. Thus, during the restoration of eutrophic shallow lakes with a high density of worms, more bivalves are needed to compensate for the negative impact of worms on water quality.
Su et al. (Thu,) studied this question.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: