Effect of Bioturbation by Freshwater Invertebrates on Nutrient Fluxes and Sediment Bacterial Community Composition04/15/2020
Bioturbation is a process by which certain animals, including, burrowing invertebrates alter sediment nutrient (only N is considered here) dynamics as well as bacterial community composition. In this study, two burrowing bioturbators (Hexagenia bilineata and Lumbriculus variegatus) with distinct modes of burrows formation were used. Sieved wetland sediment from Observatory Wetlands at Kent State University campus was used since pilot studies revealed it to be conducive for burrowing by the bioturbators of choice. The experiment was for 7 days and microcosms (transparent PVC pipes of 20 cm height and 5 cm inner diameter) were set up in triplicates for respective bioturbators and control treatments. Microcosms were filled with sediment (10cm) and topped with site water (5cm). Surface and interstitial water samples were taken every alternate day for nitrate and ammonium analysis. Sediment cores of all the microcosms were sliced at different depths at the end of the experiment and subsamples were used for potential denitrification rate (using acetylene inhibition technique) assessment, bacterial enumeration and DNA extraction (to examine bacterial community composition). Surface water nitrate data shows that H. bilineata facilitates nitrate uptake while L.variegatus releases nitrate in respect to controls, and nitrate concentrations varied significantly over dates (P<0.01) and burrower species (P<0.001). Sediment potential denitrification rate was highest for H. bilineata followed by L.variegatus and control. Presence of bioturbators increased denitrification rates and bacterial counts at greater depths. Ongoing work is focusing on assessing bacterial community composition. In conclusion, we can state that bioturbation impacts nutrient fluxes and bacterial communities.