Cindy Lee, Stuart Wakeham and John Hedges; SUNY Stony Brook, Skidaway and University of Washington

"Organic Geochemical Studies in the Southern Ocean"

As a component of the Southern Ocean Study, Cindy Lee, Stuart Wakeham and John Hedges plan to continue their cooperative studies of organic matter cycling in the water columns and surficial sediments of ocean regions key to global flux assessments. The main goals of the SO effort are: (a) to determine how the compositions and fluxes of organic materials vary regionally and seasonally within the Southern ocean, (b) to relate the above changes to biological processing of the punctuated organic input and its siliceous matrix, (c) to follow the downward diagenetic fate of planktonic remains through the water column and into the underlying sediments, with special emphasis on biochemical trends reflecting substrate quality (freshness), and (d) to holistically account for total organic matter at all stages of degradation by ¹³CNMR analysis of bulk trap and sediment samples.

Logistically, this research will involve collecting suspended and raining particulate material within the water column and from underlying sediments at several sites along the proposed study transect. Although sampling plans must be considered preliminary at this time, we expect to collect suspended particles both by plankton net tows and high volume filtration of surface water. Sinking particles will be collected with modular sediment traps deployed in arrays of four. Individual traps will be fitted with slightly flared (15"22 cm diameter) particle interceptors and indented rotating sphere valves, the latter to selectively collect sinking particles versus swimming zooplankton without loss of sample or biocide. Two of the four traps on each array will be fitted with 12 tube subsampling carousels, whereas the other pair incorporate simple bulk accumulating chambers (all treated with HgCl₂ in brine). We plan to deploy two arrays (in intermediate water and near the seafloor) on each of three moorings located at about 44, 52 and 66 S. If at all possible, we hope to piggyback on moorings deployed by Honjo/Dymond so that samples can be directly compared and obtained with minimal expense and effort, under what promise to be challenging conditions. Sediments will be collected at these same sites with particular attention given to recovering particulate material from the immediate sediment water interface.

The collected trap and sediment core samples will be analyzed for mass, elemental composition (CHN), surface area, carbon forms by ¹³CNMR, and aldoses (Hedges); as well as for individual amino acids, pigments (Lee) and lipids of various types (Wakeham). In view of the anticipated weather and sea conditions, we will need to include three persons on the trap deployment and recovery cruises. We greatly appreciate the recent rescheduling of the trap deployment cruise back to mid-November, which will allow sufficient time for construction and testing of the needed sampling equipment.