Insight into Chemical, Biological, and Physical Processes in Coastal Waters from Dissolved Oxygen and Inert Gas Tracers

Cara Manning, Ph.D., 2017
David Nicholson, Co-Advisor
Rachel Stanley, Co-Advisor

In this thesis, I use coastal measurements of dissolved O2 concentration and isotopic composition and inert gas concentrations to provide insights into the chemical, biological, and physical processes that impact the oceanic cycles of carbon and dissolved gases.  First, I developed a new field-deployable instrument for measuring noble gases in water that has precision and accuracy of 1 % or better, and higher throughput and lower cost compared to published laboratory-based methods. Second, I used time-series measurements of O2 and noble gases in Monterey Bay, California, to evaluate the performance of published air-sea gas exchange parameterizations in simulating the inert gas data and to quantify productivity. Accurately parameterizing bubble-mediated gas exchange was necessary to simulate the He and Ne measurements. I found that net community production estimated from 15NO3- uptake and O2/Ar gave equivalent results at steady state. Third, I conducted dual tracer release experiments and measured O2 during seasonal ice melt in the Bras d'Or Lake, a Canadian inland sea. The gas transfer velocity at >90 % ice cover was 6 % of the rate for ice-free conditions. Rates of volumetric gross primary production were similar when the estuary was ice-covered and ice-free.