High-resolution net and gross biological production during a Celtic Sea spring bloom

Abstract

Shelf seas represent only 10% of the ocean area, but support up to 30% of all oceanic primary production. There are few measurements of shelf-sea biological production at high spatial and temporal resolution in such heterogeneous and physically dynamic systems. Here, we use dissolved oxygen-to-argon (O2/Ar) ratios and oxygen triple isotopes (16O, 17O, 18O) to estimate net and gross biological production in the Celtic Sea during spring 2015. O2/Ar ratios were measured continuously using a shipboard membrane inlet mass spectrometer (MIMS). Additional discrete water samples from CTD hydrocasts were used to measure O2/Ar depth profiles and the δ(17O) and δ(18O) values of dissolved O2. These high-resolution data were combined with wind-speed based gas exchange parameterisations to calculate biologically driven air-sea oxygen fluxes. After correction for disequilibrium terms and diapycnal diffusion, these fluxes yielded estimates of net community (N(O2/Ar)) and gross O2 production (G(17O)). N(O2/Ar) was spatially heterogeneous and showed predominantly autotrophic conditions, with an average of (33±41) mmol m-2 d-1. G(17O) showed high variability between 0 and 424 mmol m-2 d-1. The ratio of N(O2/Ar) to G(17O), ƒ(O2), was (0.18±0.03) corresponding to 0.34±0.06 in carbon equivalents. We also observed rapid temporal changes in N(O2/Ar), e.g. an increase of 80 mmol m-2 d-1 in less than 6 hours during the spring bloom, highlighting the importance of high-resolution biological production measurements. Such measurements will help reconcile the differences between satellite and in situ productivity observations, and improve our understanding of the biological carbon pump

Reviews and syntheses: Expanding the global coverage of gross primary production and net community production measurements using BGC-Argo floats

“…5) Cynar et al, 2021;Hamme et al, 2012;L. Juranek, 2020;Li & Cassar, 2016*;Ouyang et al, 2021;Qin et al, 2021Qin et al, , 2021Seguro et al, 2019;Wang et al, 2020 NCP Ship Archived PP map (Fig. 1) Johnson, 2010;Körtzinger et al, 2008;Weeding & Trull, 2014 NCP, ANCP Mooring Archived PP map (Fig.…”

Different flavours of oxygen help quantify seasonal variations of the biological carbon pump in the Celtic Sea

“…Previous studies of biological production in the Celtic Sea with "traditional" methods do not agree well (Joint and Pomroy, 1983;Holligan et al, 1984;Joint et al, 1986;Rees et al, 1999;Joint and Groom, 2000;Joint et al, 2001;Robinson et al, 2009;Hickman et al, 2012;Poulton et al, 2014), in part because of the inherent differences of each method ( 14 C, 18 O, 15 N, fast repetition rate fluorometry (FRRF), chlorophyll a, etc.) and their known biases (e.g., artifacts associated with incubation) (Marra, 2009;Robinson et al, 2009), but also because these areas are heterogeneous dynamic systems that require higher temporal and spatial resolution than the open ocean and snapshot sampling usually fails to capture their variability (Seguro et al, 2019). While satellite observations provide high spatial and temporal coverage when there are no clouds, these observations are mostly limited to the sea surface layer.…”

Norwegian Sea net community production estimated from O<sub>2</sub> and prototype CO<sub>2</sub> optode measurements on a Seaglider

“…Carbonate system sensors suitable for autonomous deployment have been developed in the past decades, in particular pH sensors (Seidel et al, 2008;Martz et al, 2010;Rérolle et al, 2013) and p(CO 2 ) sensors (Atamanchuk et al, 2014;Bittig et al, 2012;Degrandpre, 1993;Goyet et al, 1992;Körtzinger et al, 1996). One of these sensors is the CO 2 optode (Atamanchuk et al, 2014), which has been successfully deployed to monitor an artificial CO 2 leak on the Scottish west coast (Atamanchuk, et al, 2015b), on a cabled underwater observatory (Atamanchuk et al, 2015a), to measure lake metabolism (Peeters et al, 2016), for fish transportation (Thomas et al, 2017) and on a moored profiler (Chu et al, 2020).…”

“…NCP can be quantified using bottle incubations or in situ biogeochemical budgets (Sharples et al, 2006;Seguro et al, 2019). Bottle incubations involve measuring production and respiration in vitro under dark and light conditions.…”