Sediment Trap (Process Cruise)
- Title
- Exported particulate carbon and nitrogen measurements from 4-day sediment trap deployments in the CCE region, 2007 - 2019 (ongoing).
- Abstract
- Sediment traps are used to measure particulate export flux of organic matter from the euphotic zone at various depths (up to 100), so to better understand what flows through the water column regarding food chains in the CCE. Tubes are filled with dense seawater to create a density gradient, and are attached to a wire connected to a drifting float for up to 4 days. Samples from the recovered array of the trap material (fecal matter and other sinking particles - zooplankton removed) are filtered onto precombusted filters for analyses of particulate carbon and nitrogen flux rates for each cycle in the CCE Process cruises (since 2007, ongoing)
Data
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table
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SedimentTrap
Main data table for dataset
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Rows: 74
Columns: 18
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Methods
- General Methods
- VERTEX-style drifting sediment traps (Knauer et al. 1979) were deployed at the beginning and recovered at the end of each cycle. Trap arrays consisted of 4-12 particle interceptor traps (PIT) with an inner diameter of 70-mm and aspect (height:diameter) ratio of 8:1. Each PIT had a baffle on top that consisted of 14 smaller tubes, also with an 8:1 aspect ratio. The tubes in the baffle were tapered at the top, and it was assumed that all particles within the inner diameter of the PIT descended into the trap. The traps were designed to sample settling material accurately by reating a semi-stable boundary layer immediately above the trap, while avoiding mixing and resuspension during recovery. On P0704, 8 PITs were deployed at a depth of 100 m on each cycle. On P0810 and P0904, 8-12 PITs were deployed at a depth of 100-m and 4-8 PITs were deployed at the base of the euphotic zone, except on P0810-2 and P0904-2, when the euphotic zone was close to 100 m.
Before deployment, each PIT was filled with 2.2 L of a slurry composed of filtered seawater with an additional 50 g/L NaCl to create a density interface within the tube that prevented mixing with in situ water. The traps were fixed with a final concentration of 4% formaldehyde before deployment to minimize decomposition as well as consumption by mesozooplankton grazers (Knauer et al. 1984). Upon recovery, the depth of the salinity interface was determined, and the overlying water was gently removed with a peristaltic pump until only 5 cm of water remained above the surface. The water was then mixed to disrupt large clumps and screened through a 300-um Nitex filter. Swimmers were removed from the filters under a dissecting scope, and the remaining material was returned to the sample. The tubes were then split with a Folsom
plitter, and subsamples were taken for C/N and pigment analyses. Typically, ΒΌ PIT tube samples were filtered through a pre-combusted GFF, which was acidified (to assess organic carbon) prior to combustion in the Costech 4010 elemental combustion analyzer in the SIO Analytical Laboratory. Entire tubes were typically filtered through quartz microfiber filters for C:234Th analyses as described above. Triplicate subsamples (typically 50 mL) were analyzed for Chl a and phaeopigment concentrations using the acid method and a Turner Designs Model 10 fluorometer (<a target="_blank" href="http://cce.lternet.edu/data/methods/">CalCOFI, Chlorophyll Methods</a>).
References
- Stukel, M.R., M.D. Ohman, C. Benitez-Nelson and M.R. Landry, Mesozooplankton contribution to vertical carbon export in a coastal upwelling system. Mar. Ecol. Prog. Ser., 491, 47-65, 2013. DOI 10.3354/meps10453. CCE LTER Contribution #0256.