The sediment trap array was deployed at the beginning and recovered at the end of each experimental cycle.The array consisted of two VERTEX-style particle interceptor tube (PIT) crosspieces (Knauer et al. 1979, Stukel et al. 2013), deployed at what investigators initially thought to be the base of the euphotic zone (100 m on cycle 1, 90 m on other cycles) and 150 m. Each crosspiece held 8-12 cylindrical trap tubes, with an inner diameter of 70 mm and an 8:1 aspect ratio. Each tube also contained a baffle constructed of 14 smaller tubes that had been tapered at the top to ensure that all particles settling within the inner diameter of the outer tube would sink into the trap. Tubes were deployed with 2 L of a slurry comprised of 0.1-um filtered seawater, amended with an additional 50 g L-1 NaCl, and formalin (1% final concentration).

Upon recovery, the height of the interface between trap slurry and overlying water was immediately determined and the overlying water was gently removed with a peristaltic pump. Samples were then gravity filtered through a 200-um mesh Nitex filter and the contents of the filter were sorted under a dissecting microscope to remove mesozooplankton that were believed to have swam into the trap. The remainder of the >200-um particles were then re-combined with the <200-um. Individual tubes were split using a Fulsom split to allow replicate measurements of multiple different components of the sinking including organic C (Corg), N, and pigments (reported in Stukel et al. 2013). Samples for pigments were filtered through GF/F filters and extracted in 90% acetone for greater than 24 hours. Chlorophyll a and phaeopigments were then determined on a Turner Designs model 10 fluorometer (Strickland and Parsons, 1972). Samples for C and N were filtered through a GF/F filter and frozen at -80C. On land, filters were cut in half and acidified with HCl for 24 hours. They were then analyzed for C and N on the CHN analyzer at the SIO Analytical Facility.

Related publications and references:
Knauer, G.A., Martin, J.H., and Bruland, K.W. (1979) Fluxes of particulate carbon, nitrogen, and phosphorus
in the upper water column of the northeast Pacific. Deep Sea Research, 26A, 97-108. doi: 10.1016/0198-0149(79)90089-X
Stukel, M. R., Decima, M. ,Selph, K. E., Taniguchi, D. A. A., Landry, M. R. (2013) The role of Synechococcus in vertical flux in the Costa Rica upwelling dome. Progress in Oceanography 112-113: 49-59. doi: 10.1016/j.pocean.2013.04.003