According to our precruise operational strategy, all sites occupied during Leg 201 were previously cored during either ODP or DSDP expeditions. Each site was selected to define specific yet contrasting biogeochemical and sedimentary environments to address the fundamental questions regarding microbial communities and activities outlined in our cruise objectives. One outstanding operational result was the improved quality of core recovered relative to previous expeditions as a result of technological advancements in tools and modified coring and core handling techniques. At each site occupied, APC coring was pushed to significantly greater depths than achieved during previous occupations, thus providing cores with much less drilling disturbance than XCB cores (Table T1). This recovery was critical to meeting our geochemical and microbiological objectives, inasmuch as drilling disturbance that is endemic to XCB cores would have radically increased the potential of contamination of the cores with surface seawater.
At many of our sites where subseafloor temperatures are well below ambient surface temperatures, thermal equilibration of the cores was a concern. With the cooperation of the rig floor personnel and technical staff, two shipboard strategies were developed to combat excessive core warming. Instead of the standard operational protocol of sleeving core barrels on the rig floor while a core barrel was deployed, the core was delivered to the catwalk as soon as the drill pipe was secure. This process required additional time and effort to reopen the drill string and deploy the next core barrel after core handling, but it minimized as much as possible the amount of time cores were exposed to ambient temperatures (consistently 25° to 27°C during the entire expedition). Subsections of cores intended for microbiological sampling were then transferred to either the hold refrigerator or the core locker, which were both regulated to 4°C. All microbiological subsampling was performed in the 4°C refrigerators, thus ensuring that organisms adapted to low subseafloor temperatures were protected from overheating.
Discussions with the ODP Engineering Development Team prior to Leg 201 led to an agreement to deploy the redesigned PCS at least twice in a functional test mode at each of our first sites and to use the outcome of those tests to plan an operational strategy for further deployments at intervals of scientific interest during coring at subsequent sites. This program resulted in 17 deployments of the tool at six sites, most of them recovering core under pressure (Table T2). In addition, a specific experiment was designed at Site 1230, where a methane concentration profile was derived from multiple deployments.
By agreement between ODP and developers of the third-party pressure coring device termed HYACE, two engineers from Fugro Engineers B.V. joined the JOIDES Resolution at our shallow-water sites (1227, 1228, and 1229). We incorporated functional tests of the tool into our operational strategy, planning minimally six but potentially as many as nine tool deployments (an average of three per site) to provide the Fugro engineers data from which to derive an operational strategy for ODP Leg 204. Seven deployments were realized (Table T3) before the tool was damaged beyond our ability to repair at sea. However, we believe the intent and goals of the agreed deployment strategy were met and even exceeded during our operations.
Downhole temperature profiles were augmented at six of our seven sites using the DVTP. In situ pressure measurements were attempted at all seven of the sites using the DVTP-P. The DVTP was deployed 18 times and returned a usable temperature profile in 12 cases. The DVTP-P was deployed 10 times. However, because of a series of mechanical malfunctions, shallow-water drill string behavior, and inhospitable formation conditions, only one record was considered reliable. Even this record did not have the characteristic spike and decay pattern recorded during previous deployments of the tool.
The APC-M tool was deployed at six of our seven sites. Data from these deployments will be evaluated postcruise, but initial observations suggest the electronics package was damaged in one of the early runs and data quality in subsequent deployments was compromised.
Perfluorocarbon tracer was pumped continuously throughout all coring operations during Leg 201 to monitor the potential of drilling fluid (surface seawater) contamination in cores sampled for microbiological studies. The tracer was metered into the circulation fluid system in a constant concentration (per Smith et al., 2000b) regulated by the shipboard rig instrumentation software. In 21.7 days of coring operations, we consumed 22 canisters of PFT. For future operations with microbiological objectives, this consumption rate should be considered in precruise planning.
In addition to PFT, which indicated the potential for drilling fluid contamination in cores, fluorescent microspheres were deployed on individual cores to indicate whether or not microbe-sized particles might have infiltrated samples. The microspheres (in a suspension of deionized water) were transferred into a plastic bag that was installed in the core catcher. After several of the bags failed to rupture, the attachment geometry was modified by wedging both ends of the plastic bag into a shim above the core catcher and stretching the bag across the throat of the core barrel. The modified attachment geometry resulted in confirmed delivery of the microspheres on every subsequent deployment. Microspheres were deployed on 53 cores during Leg 201. For future reference, most of these were with dilute suspensions with six aliquots of diluted microspheres prepared from each bottle of concentrate. Early deployments included undiluted suspensions, but we chose to use dilutions starting at our second site in order to conserve stock for later deployments. Stock on board at the beginning of Leg 201 was 24 bottles of concentrated microspheres; we used 22 bottles and could have used significantly more.
In preparation for Leg 204, a thermal imaging IR camera was tested at many of the sites occupied during Leg 201. During H2S alert status, camera operation was suspended because of restrictions on the number of personnel allowed on the catwalk and the potential of cable and air hose entanglement. The camera performed well and provided a unique data set for Leg 201. However, future deployments of this system should include a less intrusive and less labor intensive operational protocol.
For the first time in the history of ODP, radiotracer experiments were conducted in a van dedicated to this purpose. Routine monitoring during the expedition confirmed that work surfaces within the van remained free of contamination and, furthermore, that no contaminating radioactivity was carried outside of the van to other parts of the vessel.
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