Dataset: Biogenic Silica - Sediment Traps

Particle export was measured using a free-drifting sediment trap array. Prior to deployment, acrylic collector tubes fitted with entrance baffles comprised of 14 smaller tubes with tapered edges were filled with a saltwater brine (0.1-um filtered surface seawater, amended with 50 g L-1 NaCl and 1% final concentration formalin). Tubes were deployed at two depths (90 or 100 m, and at 150 m) for ~four days of collection. After recovery, samples were filtered through a 200-um filter, and swimming zooplankton were sorted microscopically and removed from the >200-um fraction, which was then recombined with the <200-um fraction. Three different tubes thus cleared of swimmers were subsampled using a rotary splitter for measurement of biogenic silica concentration. These subsamples were filtered through 0.6-um polycarbonate membranes, placed in cryovials, and dried in an oven for ~24 h. On shore, quantification of biogenic silica concentration was done using a NaOH digestion procedure in Teflon tubes, which provides low and stable blanks. The calculation of biogenic silica export was done after correcting for the fraction of the tube subsampled and divided by the trap area and deployment time.