Coccolithophore community response to ocean acidification and warming in the Eastern Mediterranean Sea : results from a mesocosm experiment

Unidad de excelencia María de Maeztu CEX2019-000940-MMesocosm experiments have been fundamental to investigate the effects of elevated CO and ocean acidification (OA) on planktic communities. However, few of these experiments have been conducted using naturally nutrient-limited waters and/or considering the combined effects of OA and ocean warming (OW). Coccolithophores are a group of calcifying phytoplankton that can reach high abundances in the Mediterranean Sea, and whose responses to OA are modulated by temperature and nutrients. We present the results of the first land-based mesocosm experiment testing the effects of combined OA and OW on an oligotrophic Eastern Mediterranean coccolithophore community. Coccolithophore cell abundance drastically decreased under OW and combined OA and OW (greenhouse, GH) conditions. Emiliania huxleyi calcite mass decreased consistently only in the GH treatment; moreover, anomalous calcifications (i.e. coccolith malformations) were particularly common in the perturbed treatments, especially under OA. Overall, these data suggest that the projected increase in sea surface temperatures, including marine heatwaves, will cause rapid changes in Eastern Mediterranean coccolithophore communities, and that these effects will be exacerbated by OA

Biogeochemical relationships between ultrafiltered dissolved organic matter and picoplankton activity in the Eastern Mediterranean Sea

Author Posting. © The Author(s), 2009. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part II: Topical Studies in Oceanography 57 (2010): 1460-1477, doi:10.1016/j.dsr2.2010.02.015.We targeted the warm, subsurface waters of the Eastern Mediterranean Sea (EMS) to investigate processes that are linked to the chemical composition and cycling of dissolved organic carbon (DOC) in seawater. The apparent respiration of semi-labile DOC accounted for 27 ± 18% of oxygen consumption in EMS mesopelagic and bathypelagic waters; this value is higher than that observed in the bathypelagic open ocean, so the chemical signals that accompany remineralization of DOC may thus be more pronounced in this region. Ultrafiltered dissolved organic matter (UDOM) collected from four deep basins at depths ranging from 2 to 4350 m exhibited bulk chemical (1H-NMR) and molecular level (amino acid and monosaccharide) abundances, composition, and spatial distribution that were similar to previous reports, except for a sample collected in the deep waters of the N. Aegean Sea that had been isolated for over a decade. The amino acid component of UDOM was tightly correlated with apparent oxygen utilization and prokaryotic activity, indicating its relationship with remineralization processes that occur over a large range of timescales. Principal component analyses of relative mole percentages of monomers revealed that oxygen consumption and prokaryotic activity were correlated with variability in amino acid distributions but not well correlated with monosaccharide distributions. Taken together, this study elucidates key relationships between the chemical composition of DOM and heterotrophic metabolism.TBM and AG acknowledge funding from the Hellenic GSRT/European Union (non-EU Grant No180) and SESAME Project (European Commission's Sixth Framework Program, EC Contract No GOCE-036949). TY was supported by the Japanese Society for the Promotion of Science (JSPS) Postdoctoral Fellowship for research abroad and DDC received a fellowship of the University of Groningen. Microbial laboratory work and molecular analyses were supported by a grant of the Earth and Life Science Division of the Dutch Science Foundation (ARCHIMEDES project, 835.20.023) to GJH. DJR and TBM were supported by grants from the Gordon and Betty Moore Foundation and from the C-MORE organization of NSF

A multi-decade record of high quality fCO2 data in version 3 of the Surface Ocean CO2 Atlas (SOCAT)

The Surface Ocean CO2 Atlas (SOCAT) is a synthesis of quality-controlled fCO2 (fugacity of carbon dioxide) values for the global surface oceans and coastal seas with regular updates. Version 3 of SOCAT has 14.7 million fCO2 values from 3646 data sets covering the years 1957 to 2014. This latest version has an additional 4.6 million fCO2 values relative to version 2 and extends the record from 2011 to 2014. Version 3 also significantly increases the data availability for 2005 to 2013. SOCAT has an average of approximately 1.2 million surface water fCO2 values per year for the years 2006 to 2012. Quality and documentation of the data has improved. A new feature is the data set quality control (QC) flag of E for data from alternative sensors and platforms. The accuracy of surface water fCO2 has been defined for all data set QC flags. Automated range checking has been carried out for all data sets during their upload into SOCAT. The upgrade of the interactive Data Set Viewer (previously known as the Cruise Data Viewer) allows better interrogation of the SOCAT data collection and rapid creation of high-quality figures for scientific presentations. Automated data upload has been launched for version 4 and will enable more frequent SOCAT releases in the future. High-profile scientific applications of SOCAT include quantification of the ocean sink for atmospheric carbon dioxide and its long-term variation, detection of ocean acidification, as well as evaluation of coupled-climate and ocean-only biogeochemical models. Users of SOCAT data products are urged to acknowledge the contribution of data providers, as stated in the SOCAT Fair Data Use Statement. This ESSD (Earth System Science Data) “living data” publication documents the methods and data sets used for the assembly of this new version of the SOCAT data collection and compares these with those used for earlier versions of the data collection (Pfeil et al., 2013; Sabine et al., 2013; Bakker et al., 2014). Individual data set files, included in the synthesis product, can be downloaded here: doi:10.1594/PANGAEA.849770. The gridded products are available here: doi:10.3334/CDIAC/OTG.SOCAT_V3_GRID