Dataset: Gulf of Mexico sediment trap
Deployment: NF1704

Methodology: 

Data comes from VERTEX-style, surface-tethered, drifting sediment trap deployments.  Particle interceptor tubes were deployed on cross-pieces with 8 tubes attached.  Tubes were deployed with a dense formaldehyde brine created by adding NaCl and formaldehyde to filtered seawater.  After recovery, overlying seawater was removed from each cruise by gentle suction.  Tubes were then gravity filtered through a 100-micron nitex mesh filter, and the 100-micron filters were carefully analyzed under a stereomicroscope and all metazoan zooplankton “swimmers” were removed from the sample.  Material remaining on the 100-micron filters (i.e., sinking material) was then imaged with a macrophotography rig and subsequently rinsed back into the original sample tube (i.e., re-combined with the <100-micron sinking material).  Samples were then separated and filtered onto different types of filters for a suite of different analyses including: particulate organic carbon flux, particulate nitrogen flux, carbon and nitrogen isotopes, chlorophyll a and phaeopigment flux, and 234Th flux.

Sampling and analytical procedures:

Samples for particulate organic carbon flux were vacuum filtered through pre-combusted GF/F filters at low pressure.  Samples were then frozen at -80C and stored for the duration of the cruise.  They were then dried out for shipping.  On land they were acidified by fuming with HCl.  Samples were then thoroughly dried and packed into pre-combusted tin cups.  They were analyzed by isotope ratio mass spectrometer at the UC Davis Stable Isotope Facility for carbon, nitrogen, carbon isotopes, and nitrogen isotopes.

Samples for Chl a and phaeopigments were filtered onto GF/F filters, extracted in acetone, and analyzed by the acidification method using a Turner 10-AU fluorometer.
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Samples for 234Th were filtered onto quartz (QMA) filters, mounted in RISO filter holders, and analyzed using a low-background RISO beta multi-counter.