Sludge bioreactor microcosm study on complex bacterial communities and ecosystem function using 3-CA disturbance at varying frequencies for 35 days

A stronger temporal decrease in a-diversity at the extreme, undisturbed and press-disturbed, ends of the disturbance range led to a hump-backed pattern, with the highest diversity found at intermediate levels of disturbance. Undisturbed and press-disturbed levels displayed the highest community and functional similarity across replicates, suggesting deterministic processes were dominating. The opposite was observed amongst intermediately disturbed levels, indicating stronger stochastic assembly mechanisms.

Trade-offs were observed in ecosystem function between organic carbon removal and both nitrification and biomass productivity, as well as between diversity and these functions. Hence, not every ecosystem function was favoured by higher community diversity. Our results show that the assessment of changes in diversity, along with the underlying stochastic-deterministic assembly processes, is essential to understanding the impact of disturbance in complex microbial communities.