Enabling High Quality Oxygen Measurements during Robotic Based Studies of Ocean Ecological and Biogeochemical Processes

Dissolved oxygen is an essential parameter necessary for understanding marine ecological and biogeochemical processes. New robotic vehicles and autonomous platforms are being applied to an even wider range of ecological and biogeochemical studies. Thus, arises the opportunity for matching the best possible oxygen sensing techniques and methods to these new platforms. In so doing, we can enable both more targeted and higher resolution oxygen measurements than previously possible and potentially use oxygen measurements for a wider range of applications, including in situ incubation experiments and primary productivity measurements. This thesis tested three different oxygen sensors in a trade study for stability, accuracy, precision, drift and detection limits. This thesis also conducted an iron oxidation field application study in order to fully understand the obstacles and difficulties that occur when utilizing and deploying oxygen sensors. The iron oxidation field study determined an average dissolved iron half life of approximately 4.2 hrs. The kinetic rate of iron oxidation at Lo’ihi was then compared to other known sites. The comparison revealed Lo’ihi to have a slower oxidation rate than most other sites. This is likely due to the fact that Lo’ihi is located in the oxygen minimum zone

Revealing ocean-scale biochemical structure with a deep-diving vertical profiling autonomous vehicle

Vast and diverse microbial communities exist within the ocean. To better understand the global influence of these microorganisms on Earth\u27s climate, we developed a robot capable of sampling dissolved and particulate seawater biochemistry across ocean basins while still capturing the fine-scale biogeochemical processes therein. Carbon and other nutrients are acquired and released by marine microorganisms as they build and break down organic matter. The scale of the ocean makes these processes globally relevant and, at the same time, challenging to fully characterize. Microbial community composition and ocean biochemistry vary across multiple physical scales up to that of the ocean basins. Other autonomous underwater vehicles are optimized for moving continuously and, primarily, horizontally through the ocean. In contrast, Clio, the robot that we describe, is designed to efficiently and precisely move vertically through the ocean, drift laterally in a Lagrangian manner to better observe water masses, and integrate with research vessel operations to map large horizontal scales to a depth of 6000 meters. We present results that show how Clio conducts high-resolution sensor surveys and sample return missions, including a mapping of 1144 kilometers of the Sargasso Sea to a depth of 1000 meters. We further show how the samples obtain filtered biomass from seawater that enable genomic and proteomic measurements not possible through in situ sensing. These results demonstrate a robotic oceanography approach for global-scale surveys of ocean biochemistry