Abstract
AbstractSelective removal of nitrogen (N) and phosphorus (P) from the marine dissolved organic matter (DOM) pool has been reported in several regional studies. Because DOM is an important advective/mixing pathway of carbon (C) export from the ocean surface layer and its non‐Redfieldian stoichiometry would affect estimates of marine export production per unit N and P, we investigated the stoichiometry of marine DOM and its remineralization globally using a compiled DOM data set. Marine DOM is enriched in C and N compared to Redfield stoichiometry, averaging 317:39:1 and 810:48:1 for C:N:P within the degradable and total bulk pools, respectively. Dissolved organic phosphorus (DOP) is found to be preferentially remineralized about twice as rapidly with respect to the enriched C:N stoichiometry of marine DOM. Biogeochemical simulations with the Biogeochemical Elemental Cycling model using Redfield and variable DOM stoichiometry corroborate the need for non‐Redfield dynamics to match the observed DOM stoichiometry. From our model simulations, preferential DOP remineralization is found to increase the strength of the biological pump by ~9% versus the case of Redfield DOM cycling. Global net primary productivity increases ~10% including an increase in marine nitrogen fixation of ~26% when preferential DOP remineralization and direct utilization of DOP by phytoplankton are included. The largest increases in marine nitrogen fixation, net primary productivity, and carbon export are observed within the western subtropical gyres, suggesting the lateral transfer of P in the form of DOP from the productive eastern and poleward gyre margins may be important for sustaining these processes downstream in the subtropical gyres.
Highlights
Marine geochemists have long used the Redfield ratio to link nutrient cycles of nitrogen (N) and phosphorus (P) to fixed carbon (C), allowing quantification of carbon export by applying a fixed ratio of C:N:P for organic matter over regional to global scales
In each of the plots that follow neutral density layers can be related to typical depths/water masses in the water column as follows: Surface waters within the euphotic zone of the low to mid latitudes are found at γn = 22.0 – 24.0 in the IndoPacific and at γn = 22.0 – 25.0 in the Atlantic, between the surface waters and the start of the main thermocline at γn = 26.0 lie upper thermocline and mode waters, the main thermocline lies between γn = 26.0 – 27.0, followed by intermediate water masses (e.g. Antarctic Intermediate Water, Subpolar Mode Waters) within γn = 27.0 – 27.5
We investigated the effects of non-Redfield Dissolved organic matter (DOM) dynamics and preferential dissolved organic phosphorus (DOP) remineralization on the marine biogeochemical processes of net primary productivity, nitrogen fixation, and carbon export at the global scale by comparison of REDFIELD and VAR DOM in steady-state after 310 year simulations
Summary
Marine geochemists have long used the Redfield ratio to link nutrient cycles of nitrogen (N) and phosphorus (P) to fixed carbon (C), allowing quantification of carbon export by applying a fixed ratio of C:N:P for organic matter over regional to global scales. Martiny et al, 2013a; 2013b] as well as the smaller-sized (
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
