Effects of Macrofaunal Recolonization on Biogeochemical Processes and Microbiota—A Mesocosm Study

Macroinvertebrates are widespread in lake sediments and alter sedimentary properties through their activity (bioturbation). Understanding the interactions between bioturbation sediment is important given that lakes sinks sources of carbon nutrients. We studied biogeochemical impact macrofauna on surface 3-month-long mesocosm experiments conducted using cores from a hypoxic, macrofauna-free basin. Experimental units consisted hypoxic controls, oxic treatments, treatments were experimentally colonized with chironomid larvae or tubificid worms. Overall, presence O2 bottom water had strongest geochemical effect led to oxidation down 2 cm depth. Relative increased pore concentrations nitrate sulfate lowered porewater reduced metals (Fe2+, Mn2+), presumably by burrow ventilation, whereas worms redox potential, possibly reworking. Microbial communities very similar across treatments; however, fractions α-, β-, γ-Proteobacteria Sphingobacteriia increased, those Actinobacteria, Planctomycetes, Omnitrophica decreased compared controls. Sediment microbial were, moreover, distinct macrofaunal tubes feces. suggest that, under conditions studied, oxygenation has stronger lacustrine than bioturbation.