High-resolution net and gross biological production during a Celtic Sea spring bloom. (October 2019)

• Record Type: Journal Article
• Authors: Seguro, Isabel; Marca, Alina D.; Painting, Suzanne J.; Shutler, Jamie D.; Suggett, David J.; Kaiser, Jan
• Is Part Of: Progress in oceanography. Volume 177(2019)
• Publication Date: 2019-10
• Subjects: Net community production -- Gross production -- O2/Ar ratio -- Oxygen triple isotopes -- Shelf seas -- Spring bloom; Oceanography -- Periodicals; 551.4605
• DOI: 10.1016/j.pocean.2017.12.003
• Languages: English
• ISSNs: 0079-6611

Abstract

Highlights: Net community and gross production rates during a spring bloom at high resolution. Results apply to the mixed layer and below up to the euphotic zone. N (O2 /Ar) was spatially heterogeneous and shows autotrophic conditions. Gross production rates based on oxygen triple isotopologues were up to 424 mmol m −2 d −1 . Carbon export efficiency much higher on the shelf sea than off the shelf. 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 ( 16 O, 17 O, 18 O) 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 ( 17 O) and δ ( 18 O) 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 ( 17 O)). N (O2 /Ar) was spatially heterogeneous and showed predominantly autotrophic conditions, with an average of (33 ± 41) mmol m −2 d −1 . G ( 17 O) showed high variability between 0 and 424 mmol m −2 d −1 . The ratio of N (O2 /Ar) to G ( 17 O), 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 <6 h 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.