Organic Geochemical Flux Studies in the Equatorial Pacific Using Swimmer-Excluding Rotator Traps

Stuart G. Wakeham, Cindy Lee and John I. Hedges

Goal: To quantitatively evaluate the dynamics of particles through the water column and into surface sediments in the equatorial North Pacific as reflected by their organic composition, and to determine relative reactivities for different molecular organic substances. The approach includes measurements of lipids, amino acids, and carbohydrates obtained in floating and moored sediment traps and in surface sediments obtained along the latitudinal transect across the equator.

Measurements, Protocols etc:

  1. Sample Types: A variety of particle samples will be collected in the water column, including: 1) large volume in-situ filtration samples in surface waters near the chlorophyll maximum at each survey station (coordinated with J. K. B. Bishop), 2) particulate matter sinking out of the euphotic zone (100 m depth) collected by floating sediment traps (coordinated with J. W. Murray and J. Newton), and 3) particles collected in moored sediment traps at about 1,000 m below the sea surface and 1,000 m off the bottom (coordinated with S. Honjo and J. Dymond). The large-volume filtration samples and floating sediment trap samples will be collected on both survey cruises, while the moored trap samples will be collected at stations located at 9° and 5°N and at the equator (coordinated with M. Leinen). Bottom sediments will be collected from box cores at all sites of the benthic cruise. Depending on time available, we also hope to obtain vertical profiles of size-fractionated large-volume filtration samples at the three moored-trap sites (with J. K. B. Bishop).
  2. Cruise Personnel: 
     
   Moored trap deployment and recovery - Peter Hernes (UW)
     Survey  No. 1    John Hedges (U.W.) and Michael Peterson (UW)
     Survey  No. 2    Stuart Wakeham (Skidaway) and Michael Peterson (UW)
   Benthic Cruise - Brian Bergamaschi (UW)
  3. Analyses: Particle and sediment samples will be analyzed for a wide range of major biochemical properties: 1) lipids by extraction, fractionation, and gas chromatography and gas chromatography/mass spectrometry (Wakeham); 2) amino acids by hydrolysis and HPLC analysis of OPA fluorescent derivatives (Lee); 3) aldoses and cyclitols by acid hydrolysis and GC and GC/MS analysis of peracetate or TMS derivatives (Hedges); 4) elemental composition by CHN analysis (Hedges). We plan to provide aliquots of particle and trap samples to J. K. B. Bishop (elemental composition), J. R. Murray/J. Newton (pigments, elemental composition, radionuclides), and R. Bidigare (isotopic composition of pigments) if sample sizes are adequate.

  4. QA/QC: An intercomparison of elemental compositions of samples will be made with other EqPac investigators. We also intend to archive large amounts of sediment for eventual use as organic geochemical ``reference materials.'' However, because the molecular organic measurements to be carried out by our groups are practiced in a limited number of laboratories worldwide and because standard reference materials are not available, the corresponding QC strategies must be individualistic at this point pending the development of protocols and reference materials as suggested by the recent FRECLES Workshop.