New technology for uncontaminated and pressure controlled deep-sea sampling: 'Deep Ocean Benthic Sampler' (DOBS)

Understanding of deep sea microbial ecology is substantially limited by the absence of a sampling technology that collects and maintains uncontaminated samples while maintaining the sample native pressure. This thesis describes the design of a novel Deep Ocean Benthic Sampler (DOBS) which addresses the twin challenges of contamination and pressure control by employing a controllable liquid and gas interface between the collection probe and marine environment to be sampled. This is the first device which can retrieve live, uncontaminated samples from the deep ocean floor while maintaining their native pressure.;Contamination is solved by using a snubbing fluid chamber to protect the sample chamber's entrance during its descent to the ocean floor. A pre-calculated volume of highly compressed gas is then used to evacuate the snubbing fluid leaving a pristine entrance to the sample chamber. A sampling probe is then extended through the resulting gas filled conduit, returning with the sample. Collectively, the sample chamber and conduit comprise a sterile and controllable gas/fluid interface.;The sample acquisition device (SAD) design has been specifically configured to take benthic boundary layer sediment and slurry core samples. A novel SAD probe mechanism was developed that locks the sediment cores into a sample tube and prevents loss of the sample. The tip of the SAD probe rotates closed after the sample has been taken and retracts back into the sampler.;When used at depth, DOBS requires the use of gases at extreme pressures where their behavior is not adequately described by known gas laws. A custom designed apparatus was created to empirically measure previously unknown gas compressibility factors that were needed for the DOBS design.;Finally, DOBS also offers an alternative function as a long term deployable instrumentation platform. The sample chamber can be reconfigured from holding a core sampling probe to containing a rosette holding a variety of interchangeable sensor probes. These can be repeatedly extended from DOBS, which can be filled with argon gas to minimize bio-fouling and greatly extend the operating life of these instruments. By providing a long term sensor housing, repeated deployments can be avoided saving significant expense.