Dataset: sediment trap flux
Deployment: KN207-03

Refer to Collins et al., Global Biogeochem. Cycles (2015), in review. Excerpted from methods section:

Vertically sinking particulate carbon fluxes were measured at 50, 150, and 300 meters using surface-tethered cylindrical sediment traps (0.0125 m2 cross-sectional area; materials and construction as described in McDonnell and Buesseler, 2012). A mooring consisting of four traps at each depth, a surface buoy, wave-action mitigation bungee cord, and several floats, was deployed at each process station and allowed to drift for 3-5 days. The quasi-Lagrangian behavior of the mooring during each deployment was confirmed by comparison of positional data obtained from an Argos satellite beacon mounted on the surface buoy with shipboard acoustic Doppler current profiler (ADCP) data from the R/V Knorr, which trailed the mooring at a range of 1-2 miles.

Traps were prepared, deployed, and recovered as described in McDonnell and Buesseler (2012). Traps were then sampled for particulate carbon in accordance with McDonnell and Buesseler (2012), except that the screened brine suspension (350 um pore size, to exclude macrozooplankton) was filtered onto a series of precombusted, 47 mm GF/F filters (0.7 um nominal pore size). Field and analytical blanks were collected at each station. Filters were immediately frozen in liquid nitrogen and then stored at -80 degrees C.

Filters from three of the four traps at each depth were used for determination of total particulate and particulate inorganic carbon (TPC and PIC, respectively). After thawing, the filters (including blanks) were first dried at 70 degrees C in a drying oven; each filter was then weighed and cut in half with precombusted stainless steel scissors. Each half was then weighed separately. One half was reserved for PIC analysis and the other reserved for determination of TPC.

For TPC, sets of filter halves were transferred to 12 mm by 20 cm precombusted quartz tubes containing copper oxide (100 mg) and elemental silver wires. The tubes were then attached to a vacuum line, evacuated, flame-sealed, and combusted at 850 degrees C for 10 h. The evolved carbon dioxide was then isolated through a series of cold traps and quantified manometrically. PIC was determined from the other set of filter halves by coulometric analysis of acidified samples using a Model CM5014 UIC Coulometric Analyzer with Carbonate Acidification Module, as described in Honjo et al. (1995). Particulate organic carbon (POC) was determined for each trap by difference of the blank-corrected TPC and PIC measurements.

POC measurements were not obtained for the first of the four stations on this cruise due to an equipment failure.

References:
Collins, J. R., B. R. Edwards, K. Thamatrakoln, J. E. Ossolinksi, G. R. DiTullio, K. D. Bidle, S. C. Doney, and B. A. S. Van Mooy (2015), The multiple fates of sinking particles in the North Atlantic Ocean, Global Biogeochem. Cycles, in review.

McDonnell, A. M. P., and K. O. Buesseler (2012), A new method for the estimation of sinking particle fluxes from measurements of the particle size distribution, average sinking velocity, and carbon content, Limnol Oceanogr-Meth, 10, 329-346, doi:10.4319/Lom.2012.10.329.

Honjo, S., J. Dymond, R. Collier, and S. J. Manganini (1995), Export production of particles to the interior of the equatorial Pacific Ocean during the 1992 EqPac experiment, DSR, 42(2–3), 831-870, doi:10.1016/0967-0645(95)00034-N.