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In this thesis, I use coastal measurements ofdissolved O₂ and inert gases to provide insight into the chemical,biological, and physical processes that impact the oceanic cyclesof carbon and dissolved gases. Dissolved O₂ concentration andtriple isotopic composition trace net and gross biologicalproductivity. The saturation states of inert gases trace physicalprocesses, such as air-water gas exchange, temperature change, andmixing, that affect all gases. First, I developed afield-deployable system that measures Ne, Ar, Kr, and Xe gas ratiosin water. It has precision and accuracy of 1 % or better, enablesnear-continuous measurements, and has much lower cost compared toexisting laboratory-based methods. The system will increase thescientific community's access to use dissolved noble gases asenvironmental tracers. Second, I measured O₂ and five noble gasesduring a cruise in Monterey Bay, California. I developed a verticalmodel and found that accurately parameterizing bubble-mediated gasexchange was necessary to accurately simulate the He and Nemeasurements. I present the first comparison of multiple gastracer, incubation, and sediment trap-based productivity estimatesin the coastal ocean. Net community production estimated from¹⁵NO₃⁻ uptake and 02 /Ar gave equivalent results at steady state.Underway O₂/Ar measurements revealed submesoscale variability thatwas not apparent from daily incubations. Third, I quantifiedproductivity by O₂ mass balance and air-water gas exchange by dualtracer (³He/SF₆ ) release during ice melt in the Bras d'Or Lakes, aCanadian estuary. The gas transfer velocity at >90 % ice coverwas 6 % of the rate for nearly ice-free conditions. Rates ofvolumetric gross primary production were similar when the estuarywas completely ice-covered and ice-free, and the ecosystem was onaverage net autotrophic during ice melt and net heterotrophicfollowing ice melt. I present a method for incorporating theisotopic composition of H₂O into the O₂ isotope-based productivitycalculations, which increases the estimated gross primaryproduction in this study by 46-97 %. In summary, I describe a newnoble gas analysis system and apply O₂ and inert gas observationsin new ways to study chemical, biological, and physical processesin coastal waters.

Insight into chemical, biological, and physical processes in coastal waters from dissolved oxygen and inert gas tracers