Interspecific interactions modulate bioturbation efficiency and nutrient dynamics in freshwater benthic communities

Using the snails Filopaludina bengalensis and Gabbia orcula, along with tubificid worms and Chironomus sp., one monospecific and one combinatorial experiment were conducted in microcosms over 28 days to explore the direct and indirect interactive effects of non-predatory snails and tubificid worms on the bioturbation activity of chironomid larvae. These experiments examined how the species, whether alone or in combinations of two or three, influenced nutrient cycling in freshwater environments. On a comparative scale, the snails demonstrated higher N and P efflux than the tubificid worms and chironomid larvae, with the values normalized to biomass. At the community level, the chironomid, in combination with F. bengalensis and tubificid worms, showed a significant increase in N and P flux compared to the control. Unlike the two-species treatments, only the chironomid combined with F. bengalensis displayed higher N flux relative to the three-species treatment. Additionally, the indirect interactions of grazer snails more effectively inhibited the tube-dwelling behaviour of larvae than gallery-diffuser oligochaetes. Thus, the study reveals that species-specific functional traits and their interactions have a stronger effect on nutrient dynamics than species richness alone.