In a milestone achievement, NCCOS, the Monterey Bay Aquarium Research Institute (MBARI), and the Scripps Institution of Oceanography (SIO) deployed a coordinated "team" of five MBARI long-range autonomous underwater vehicles (LRAUVs) and two SIO WireWalkers to sample a bloom of the domoic acid–producing diatom Pseudo-nitzschia in Monterey Bay, California.

Three of the LRAUVs carried out bloom reconnaissance missions in the north, central, and southern parts of the bay to characterize the highly dynamic bloom, while the other two vehicles, each carrying a third-generation Environmental Sample Processor (3G ESP; Image 1), conducted directed sampling of the bloom based on data provided by the mapping or sentinel vehicles. The 3G-ESP LRAUVs were also capable of executing autonomous ‘patch finding/tracking/sampling’ for precise targeting.

Image 1. The main photo shows the LRAUV Makai onboard the launch and recovery support vessel in Monterey Bay. The left inset shows the 3G-ESP instrument that is integrated with the LRAUV payload just behind the vehicle’s orange nose cone. A wheel of customized sample processing cartridges is located at the rear (right inset) and are used to filter water for sample preservation or for onboard toxin analysis. Credits: main photo, Q. Shemet, MBARI; insets, G. Doucette, NCCOS.

One of the 3G-ESP instruments included a surface plasmon resonance module containing miniaturized, reusable domoic acid sensor chips developed by NCCOS and MBARI scientists (Image 1), which enabled transmission of near real-time toxin measurements while the LRAUV was underway. Such "on-the-fly" determinations of bloom toxicity were used to inform concurrent sampling by the 3G-ESP LRAUVs to preserve material for post-deployment ‘omics analyses related to the presence and expression of domoic acid synthesis genes. The power of knowing that a Pseudo-nitzschia bloom population is currently producing domoic acid cannot be understated, as this knowledge adds considerable value to the ‘omics data and contributes directly to identifying and improving our understanding of the factors that can influence toxicity of these harmful algal blooms

Simultaneous deployment of five LRAUVs requires 24/7 monitoring of all vehicles’ operational status and movements, with watch-standing pilots sending and modifying mapping/sampling missions via MBARI’s custom-designed LRAUV command and control dashboard (Image 2).

Image 2. Screen capture of MBARI LRAUV dashboard showing tracks of LRAUVs during April 2022 ECOHAB Monterey Bay experiment. Credit: J. Ryan, MBARI.

Interpretation and synthesis of real-time physical-chemical data acquired by the onboard environmental sensor package, along with regional satellite data and imagery on sea surface temperature and ocean color (Image 2), also contribute to a successful and strategically informed deployment. LRAUVs Pontus, Daphne, and Galene conducted bloom reconnaissance missions in the north, central, and south bay, respectively. LRAUVs Brizo and Makai each carried 3G-ESP instruments with sample acquisition and preservation capabilities, while a surface plasmon resonance module integrated with Makai’s 3G ESP enabled targeted, near real-time measurements of domoic acid to be executed and reported while the vehicle was underway. The inset shows VIIRS satellite-based chlorophyll imagery for the Monterey Bay region that was used along with LRAUV chlorophyll mapping data to define the location and extent of the bloom.

Capabilities of the LRAUV platform are of interest to NOAA as the agency continues to broaden and advance its investment and operational footprint of uncrewed systems. NCCOS’s participation in piloting the LRAUVs during the ECOHAB Monterey Bay deployment will contribute to NOAA’s successful implementation of this uniquely powerful, biological observing technology. The mission began on April 3 and ended on April 27.

This effort is part of an ongoing ECOHAB project led by A. Allen (UCSD) with co-investigators B. Moore and A. Lucas (UCSD), C. Anderson (UCSD and SCCOOS), J. Ryan and J. Birch (MBARI), M. Sutula (SCCWRP), and G. Doucette (NOAA/NCCOS-HML).