SAMPLING STRATEGY

General

Shipboard and shore-based researchers should refer to the interim IODP Sample, Data, and Obligations policy posted on the Web at iodp.org/data_samples.html. This document outlines the policy for distributing IODP samples and data to research scientists, curators, and educators. The document also defines the obligations that sample and data recipients incur. Access to data and core sampling during Expedition 307, or within the 1 y moratorium, must be approved by the Sample Allocation Committee (SAC). The SAC (composed of Co-Chief Scientists, Staff Scientist, and IODP Curator on shore and curatorial representative on board ship) will work with the Shipboard Scientific Party to formulate a formal expedition-specific sampling plan for shipboard and postcruise sampling.

Shipboard scientists are expected to submit sample requests 2 months before the beginning of the expedition. Sample requests may be submitted at iodp.tamu.edu/curation/samples.html. Based on sample requests (shore based and shipboard), the SAC and Shipboard Scientific Party will prepare a working cruise sampling plan. This plan will be subject to modification depending upon the actual material recovered and collaborations that may evolve between scientists during the expedition. Modifications to the sampling plan during the expedition require the approval of the SAC.

All sample frequencies and sizes must be justified on a scientific basis and will depend on core recovery, the full spectrum of other requests, and the cruise objectives. Some redundancy of measurement is unavoidable, but minimizing the duplication of measurements among the shipboard party and identified shore-based collaborators will be a factor in evaluating sample requests.

The short duration of the operations, the expected high rate of core flow inherent to shallow-water operations, and the complex scientific objectives will in general not leave time for personal sampling on board. In addition, a significant amount of cores—mainly from proposed Site PORC-03—will remain unopened when X-ray imaging (subject to implementation) reveals the presence of coral fragments. Such cores will be cut in frozen state at the shore-based core repository.

Initial MST measurements will be carried out on whole-round core sections at medium resolution (5 cm) to keep pace with the core flow rate and ascertain a real-time control on core recovery and section coverage.

Two principal objectives of sampling during Expedition 307 will be to (1) obtain high-resolution interstitial water geochemical profiles to delineate microbial reaction zones and estimate potential zones of interstitial water flow; and (2) obtain corresponding samples for a variety of microbiological and biogeochemical analysis to be performed primarily in shore-based laboratories. Sampling strategies, core flow, and subsampling for shore-based laboratories will generally follow a modified scheme developed during ODP Leg 201.

Rapid analysis of key chemical species obtained from interstitial water samples in Hole A (i.e., sulfate and methane) will be important for establishing a sampling scheme for detailed microbiological analysis in Hole B. Cores identified for microbiology need to be handled rapidly and in a manner that prevents unnecessary warming and sediment oxidation. Core sections designated for microbiological sampling will be immediately removed to a temporary cooled core sampling laboratory, where the requisite number of whole-round cores will be removed and properly stored before the remainder of the core section is returned to the normal core flow pattern.

Because of time restrictions, the primary emphasis will be on cleanly obtaining whole-round cores for shore-based experimentation. To meet expedition objectives, these will include samples for deoxyribonucleic acid (DNA) and RNA based molecular microbial techniques, biomarkers, microbial activity measurements, and bacterial cultivation. These whole-round cores will be kept frozen at –80°C or anoxically stored and cooled at +4°C and shipped immediately from Ponta Delgada, Azores. Samples for quantification of total prokaryotes (acridine orange direct counts [AODC] and fluorescence in situ hybridization [FISH]) and further interstitial water chemistry for onboard processing will also be obtained. Radiochemical experiments will not be performed onboard ship during this expedition.

The second priority, subsequent to geochemical and microbiological studies, is preliminary definition of the sedimentologic and biostratigraphic framework by visual core description and targeted low-resolution sampling of age-diagnostic species. Sampling for high-resolution studies (such as stable isotope investigations) will be carried out after the cruise at a designated sampling party. Sampling of corals and associated macrofauna will also be restricted to the shore-based sampling party.