Abstract
Physical and biogeochemical processes in the Southern Ocean are fundamental for modulating global climate. In this context, a process-based understanding of how Antarctic diatoms control primary production and carbon export, and hence global-ocean carbon sequestration, has been identified as a scientific priority. Here we use novel sediment trap observations in combination with a data-assimilative ocean biogeochemistry model (ECCO-Darwin) to understand how environmental conditions trigger diatom ecology in the iron-fertilized southern Scotia Sea. We unravel the role of diatoms assemblage in controlling the biogeochemistry of sinking material escaping from the euphotic zone, and discuss the link between changes in upper-ocean environmental conditions and the composition of settling material exported from the surface to 1,000 m depth from March 2012 to January 2013. The combined analysis of in situ observations and model simulation suggests that an anomalous sea-ice episode in early summer 2012–2013 favored (via restratification due to sea-ice melt) an early massive bloom of Corethron pennatum that rapidly sank to depth. This event drove high biogenic silicon to organic carbon export ratios, while modulating the carbon and nitrogen isotopic signals of sinking organic matter reaching the deep ocean. Our findings highlight the role of diatom ecology in modulating silicon vs. carbon sequestration efficiency, a critical factor for determining the stoichiometric relationship of limiting nutrients in the Southern Ocean.
Highlights
The Southern Ocean (SO) is one of the most productive regions in the global ocean, and through its connection with all other basins, has sparked intense debate of how this remote region modulates global climate (Falkowski et al, 1998; Sarmiento et al, 2004)
Settling material collected by a sediment trap at 1000 m depth in the South Scotia Ridge provides, for the first time, an almost complete annual cycle of diatom abundance and composition in the southern sector of the Scotia Sea
A statistical analysis of insitu data and realistic ocean biogeochemistry simulation shows that the material collected by the sediment trap reflects changes in upper-ocean environmental conditions
Summary
The Southern Ocean (SO) is one of the most productive regions in the global ocean, and through its connection with all other basins, has sparked intense debate of how this remote region modulates global climate (Falkowski et al, 1998; Sarmiento et al, 2004). In this context, phytoplankton are of utmost importance due to their critical role in ocean carbon sequestration. Phytoplankton are of utmost importance due to their critical role in ocean carbon sequestration These tiny organisms are fundamental for modulating climate change through their capacity to consume and export. While the results from this groundbreaking experiment provide invaluable information linking diatom ecology to SO biogeochemistry, other critical aspects, such as how other environmental factors (e.g., irradiance, temperature, and water column stability) control the diatom species succession remain poorly understood (Boyd, 2013)
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.
