Oxygen dynamics of marine sediments

Benthic O-2 availability regulates many important biogeochemical processes and has crucial implications for the biology and ecology of benthic communities. Further, the benthic O-2 exchange rate represents the most widely used proxy for quantifying mineralization and primary production of marine sediments. Consequently, numerous researchers have investigated the benthic O-2 dynamics in a wide range of environments. On the basis of case studies - from abyssal sediments to microbial phototrophic communities - I hereby try to review the current status on what we know about controls that interrelate with the O-2 dynamics of marine sediments. This includes factors like: sedimentation rates, bottom water O-2 concentrations, diffusive boundary layers, fauna activity, light, temperature, and sediment permeability. The investigation of benthic O-2 dynamics represents a challenge in resolving variations on temporal and spatial scales covering several orders of magnitude. Such an effort requires the use of several complementary measuring techniques and modeling approaches. Recent technical developments (improved chamber approaches, O-2 optodes, eddy-correlation, benthic observatories) and advances in diagenetic modeling have facilitated our abilities to resolve and interpret benthic O-2 dynamics. However, all approaches have limitations and caveats that must be carefully evaluated during data interpretation. Much has been learned during the last decades but there are still many unanswered questions that need to be addressed in order to fully understand benthic O-2 dynamics and the role of sediments for marine carbon cycling.