A newly designed seawater sampler promises to automate monthly water sample collection, freeing up ship and personnel resources for other research projects.

MBARI researchers have been collecting seawater samples as part of a long-term research project aboard monthly research cruises since 1989. Sampling depends heavily on personnel and ship time for deploying a CTD rosette, which collects water samples at various depths in the water column, as well as conductivity, temperature, and depth (CTD) measurements. To reduce the resources required for this data collection, MBARI engineers were tasked with designing a new water-sampling sensor that fits inside an autonomous underwater vehicle (AUV).

MBARI currently uses the large Gulper AUV for collecting seawater samples for marine microbe studies, but this vehicle requires a ship for deployment and recovery. This is where MBARI’s newer class of AUVs proves useful; the long-range AUVs (LRAUVs) are designed for remote sensing and sampling in the ocean for long periods of time, and are small enough to be deployed from a smaller vessel. But because the LRAUV has limited space, a new sampler design was necessary.

The challenge in designing this sampler was meeting the requirement of holding 15 samples within the physical constraints of the LRAUV nose cone. The LRAUV will travel through the water collecting samples at different depths. As a proof of concept, Mechanical Engineer Larry Bird designed and fabricated a sampler, nicknamed the “Sipper”, holding nine Mylar polyethylene-lined bags (similar to individual juice pouches kids get for lunch). The 100-milliliter bags have one-way valves and are arranged in a carousel. Seawater is suctioned directly into the bag through a hole in an acrylic lid covering the carousel. The carousel rotates to align each successive sampling bag with the inlet. At the targeted depths, the sampler is programmed to rotate to the next bag for sample collection.

In testing, the Sipper performed successfully, so Bird moved on to create the 15-bag sampler using MBARI’s 3D printer to fabricate the carousel. In initial tests this sampler did what it’s supposed to—rotate and collect discrete bags full of seawater—but it’s not yet working consistently. There’s a bit more troubleshooting ahead for Bird and colleagues.