Operating a High Volume Plankton Sampler from a Deep Water Autonomous Underwater Vehicle

Carl L Kaiser1, Andrew Billings1, Craig Young2, Laurel Hiebert2 and Cindy Lee Van Dover3, (1)Woods Hole Oceanographic Institution, Applied Ocean Physics and Engineering, Woods Hole, MA, United States, (2)University of Oregon, Oregon Institute of Marine Biology, Charleston, OR, United States, (3)Duke University Marine Laboratory, Marine Science and Conservation, Beaufort, NC, United States
Abstract:
During the summer of 2015, a high volume plankton sampler was placed on the Autonomous Underwater Vehicle (AUV) Sentry as part of a cruise to investigate methane seeps. The sampler was successful in collecting over 800 larvae and 130 morphotypes. Most samples were split 2:1 or 4:1, so the total collection was substantially higher. The Sentry Precision Impeller Driven Sampler (SyPRID Sampler) was designed to mount as a “backpack” for the AUV Sentry. Sentry is able to fly the sampler at precision altitude as close as 150 cm from the seafloor and in precision patterns or locations for durations of 18 hours or more. Acoustic telemetry is used to monitor both Sentry and the samplers and to tune flight profiles or sampler operation in real time. Two independent samples can be collected per dive, allowing for comparative studies.

The sampler is designed based on lessons learned from traditional tow-net systems and utilizes standard mesh net – in this case 150 micron. The sampler is impeller driven and Sentry moves at approximately 0.25m/s, resulting in little or no bow wave while maintaining an estimated flow rate of between 600 and 1000 m3/h per side. The sampler funnels plankton to a “cod end”, where restriction and expansion is used to substantially reduce fluid pressure and velocity, thereby preserving the larvae in excellent condition. Valves are used to prevent contamination when not actively sampling. Substantial co-registered data is collected during the sampling including, CTD, optical backscatter, dissolved Oxygen, redox potential, and magnetics. When sampling more than 5m above bottom, multibeam sonar data can be collected. Future work will include simultaneous photography of the bottom for low-altitude sampling missions, real-time flow rate measurement, and simultaneous collection of ADCP water column data. Future work will also likely include use in the water column. The sampler is available for use on Sentry through UNOLS.

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