The Xiamen Symposium on Marine Environmental Sciences (XMAS 2025)

BGC-Argo floats are equipped with chemical sensors and have collected more profiles of nitrate, a key nutrient controlling ocean productivity, than all prior oceanographic cruises combined. These floats are sampling at high spatiotemporal resolution and generating high-quality data, available near-real-time, thus helping elucidate biogeochemical processes in the world’s oceans. Here we present a new method to measure nitrite and thiosulfate from BGC-Argo float data by recomputing the output of the UV-spectrometer sensor, originally used to compute nitrate. Nitrite and thiosulfate are two intermediate products that mainly accumulate in oxygen-deficient zones (ODZs) as a result of microbially-mediated biogeochemical transformations. Observing changes in their concentrations interannually, over seasons, at different depths, as well as their relationships with oxygen, particulate organic carbon and pH provide clues on the variability of the main biogeochemical processes inside ODZs, but measuring all these variables concomitantly in such resolution is challenging. Our new approach allows remote observation and can be applied to existing datasets as a reanalysis. Environmental data can be then interpreted by using the float’s full suite of sensors, providing a thorough assessment of the local biogeochemistry at those locations, as we’ll demonstrate in this study.

dissolve oxygen,denitrification,nitrogen removal,organic carbon,Sulfur,Biogeochemical Argo float,ocean biogeochemisry