Shelf-sea gross and net production estimates from oxygen-to-argon ratios and triple oxygen isotopes.
Dissolved oxygen (O2) concentrations and their variations over time can be used to estimate biological net community production (NCP). However, physical process such us variations in temperature and pressure, mixing and bubble injection also influence dissolved O2 in seawater. To correct for these processes, I measured O2/Ar ratios using a shipboard membrane inlet mass spectrometer (MIMS) on board of RRS Discovery during four SSB cruises in 2014-2015 (summer-winter-spring-summer) in the Celtic Sea.
The data, together with wind speed-based gas exchange parameterisations, give biological oxygen fluxes, which, at steady-state and disregarding advection, eddy diffusion and entrainment, equal NCP.In order to calculate gross production (GP), I took discrete samples of triple oxygen isotopes.
The resulting data show variations in shelf-sea net and gross biological production with unprecedented temporal and spatial resolution. We estimate annual exchanges of carbon between the shelf sea, the atmosphere and the open ocean, as well as production rates.