TY  - JOUR
A1  - Frindte, Katharina
A1  - Eckert, Werner
A1  - Attermeyer, Katrin
A1  - Grossart, Hans-Peter
T1  - Internal wave-induced redox shifts affect biogeochemistry and microbial activity in sediments - a simulation experiment
JF  - Biogeochemistry
N2  - Internal waves (seiches) are well-studied physical processes in stratified lakes, but their effects on sediment porewater chemistry and microbiology are still largely unexplored. Due to pycnocline oscillations, sediments are exposed to recurrent changes between epilimnetic and hypolimnetic water. This results in strong differences of environmental conditions, which should be reflected in the responses of redox-sensitive biogeochemical processes at both, the sediment-water interface and deeper sediment layers. We tested in a series of mesocosm experiments the influence of seiche-induced redox changes on porewater chemistry and bacterial activity in the sediments under well controlled conditions. Thereby, we excluded effects of changes in current and temperature regimes. For a period of 10 days, intact sediment cores from oligotrophic Lake Stechlin were incubated under constant (either oxic or anoxic) or alternating redox conditions. Solute concentrations were measured as porewater profiles in the sediment, while microbial activity was determined in the upper 0.5 cm of sediment. Oxic and alternating redox conditions resulted in similar ammonium, phosphate, and methane porewater concentrations, while concentrations of each analyte were considerably higher in anoxic cores. Microbial activity was clearly lower in the anoxic cores than in the oxic and the alternating cores. In conclusion, cores with intermittent anoxic phases of up to 24 hours do not differ in biogeochemistry and microbial activities from static oxic sediments. However, due to various physical processes seiches cause oxygen to penetrate deeper into sediment layers, which affects sediment redox gradients and increase microbial activity in seiche-influenced sediments.
KW  - Internal waves
KW  - Sediment
KW  - Sediment-water interface
KW  - Core incubation experiments
KW  - Porewater profiles
KW  - Redox conditions
KW  - Microbial activities
Y1  - 2013
U6  - https://doi.org/10.1007/s10533-012-9769-1
SN  - 0168-2563
VL  - 113
IS  - 1-3
SP  - 423
EP  - 434
PB  - Springer
CY  - Dordrecht
ER  -