The BOXER Lander (Benthic OXygen Exchange Rates) Lander
This lander supports sensors measuring near-bed velocities and dissolved oxygen to derive eddy correlation fluxes. A high resolution pivoting digital camera provides time-series images of the sediment surface area that contributes to the flux.
Reference: Reimers, C. E., H. T. Özkan-Haller, P. Berg, A. Devol, K. McCann-Grosvenor, and R. D. Sanders (2012), Benthic oxygen consumption rates during hypoxic conditions on the Oregon continental shelf: Evaluation of the eddy correlation method, J. Geophys. Res., 117, doi:10.1029/2011JC007564.
Microelectrode Profiler in Different Modes of Deployment
Pore Water and Solid Phase Chemistry
Collecting surface sediments without disturbance and loss of the overlying bottom water is difficult especially when sediments are sandy. Collaborating with Rob Wheatcroft (OSU biological oceanographer) we recently built a hydraulically dampened slow-gravity corer capable of collecting the uppermost ~50 cm of most sediment columns with little disturbance. The corer can be equipped with video and digital still cameras to monitor the coring process and to photograph bottom features. The samples obtained with the corer are used for extracting and analyzing constituents in pore waters and in solid phases (e.g., dissolved nutrients, sulfate, sulfide, total-CO2; solid-phase organic C, CaCO3, acid volatile-S, pyrite, 210Pb).
Incubation methods help to constrain the rates of diagenetic transformations. Incubation methods include benthic chambers, core incubations and the incubations of interval samples from sediment cores and/or water samples. Through collaboration with Al Devol (UW) benthic chamber incubations were performed on the Oregon shelf at 50-150 meters depth in June and August 2009 and oxygen fluxes have been compared to those derived by eddy correlation (Reimers et al., 2012). Chamber oxygen and nitrate fluxes were into the sediments while silicate, iron and ammonium fluxes were out of the sediments which were composed predominantly of fine sand (Fuchsman et al., in prep.).
On more recent cruises we have been working with Sean Crowe (University of Southern Denmark) who has conducted incubations to measure: 1) denitrification, anammox, Dissimilatory Nitrate Reduction to Ammonium (DNRA), nitrification, NOx- and NH4+ fluxes, 2) total sediment respiration; and 3) sulfate reduction and pyrite formation. Additional samples were collected from both the water column and sediment for molecular microbial work. When combined these approaches will help us to relate the rates of sediment transformations off Oregon to regional and global elemental cycles.