Nutrient turnover in sediments and role of methanogenic C in food web
This research programme focuses on the detailed study of complex water movements in and above the sediments, which have a key influence on sediment/particle physics and chemistry. We study (1) the transformations of C, P, and Fe on the gradient of settling seston – sediment diagenesis; (2) the role of the different electron acceptors in the particle-associated C, P, Fe cycling; (3) the importance of sediment disturbances or flush events for the freshwater ecosystem; (4) the fate of bioavailable Fe in reservoirs; and (5) the overall methane emission from temperate reservoirs.
How does the nutrient input in sediments relate to particle and sediment behavior? How does this affect geochemistry of major elements and greenhouse gas emission?
Water movement in and above the sediments has key influence on sediment/particle physics and chemistry. Even though the instruments for water movement measurements underwent large development towards higher sensitivity and smaller dimensions, it is still not very common to combine both hydraulics and biogeochemical research in freshwater ecosystems. The key approach of our research is to extrapolate well-established descriptive methods of particle/sediment composition using the information about water movement. Using this approach, we will receive information about the spatial and temporal distribution of the observed processes. We aim to cover whole reservoirs from their inflow to the dam part, but most of the effort is concentrated on the shallow/inflow parts, where the processes between the sediment and water are considered to be more important.
We use the experimental simulation approach of sediment behaviour under “typical situations”, i.e. weather or season. Sediment incubations under different mixing velocities, manipulation of water composition above the sediment, as well as selected temperature and atmosphere conditions are already used successfully. We plan to conduct both short-term and long-term data collection campaigns to receive as much information about the water composition and movements as possible. Simultaneously, the in-situ sediment properties are described and/or short-term settling seston traps set to sample the “particulate” material. Sediment / particle biogeochemical properties are characterised by either specific extraction methods [Jan et al. 2013, 2015] or direct compound analyses using LC-ICP-QQQ, GC, LC, or IRMS instruments.