Millennial surface water dynamics in the Ría de Vigo during the last 3000 years as revealed by coccoliths and molecular biomarkers

13 pages, 7 figures, 2 tables.-- Printed version published Mar 10, 2005.A combined study of coccolith assemblages and biomarkers in a gravity core collected from the Ría de Vigo (NW Spain) allowed us to reconstruct the paleoenvironmental conditions for the last 3000 years. The quantitative distribution of coccolithophore species points to three different intervals within the core, dated by AMS radiocarbon measurements. The first interval (ca. 975 BC–252 AD), characterized by high abundances of Calcidiscus leptoporus and Gephyrocapsa muellerae, is thought to represent moderate water temperatures, suggesting a transition from a warmer to a cooler period. The second interval (ca. 252–1368 AD), characterized by the dominance of Coccolithus pelagicus, Helicosphaera carteri and Syracosphaera spp., and a high concentration of hexacosanol linked to terrestrial input, is interpreted as having been a humid period with fluvial input. The third interval (ca. 1368 AD–1950) is characterized by a high abundance of Gephyrocapsa oceanica, high alkenone values and low values of hexacosanol, and is thought to represent a period dominated by oceanic conditions within the Ría.Taking into account the ocean–atmospheric system affecting the region studied, here we propose an alternation in the mean state of North Atlantic Oscillation (NAO) at millennial time scales. A well-developed upwelling system and an active Ría–ocean connection during the warmer interval I suggest a NAO+ phase influenced by a Hypsithermal period. The occurrence of the humid and relatively warm interval II is consistent with a negative phase in the NAO, as well as a relative restriction in ocean–Ría exchange. Interval III, which was drier and more productive, again suggests the dominance of a positive phase in the NAO, with a more intense oceanic connection and more energized upwelling.Research grants ABRUMIS REN2003-08642-C02-02/CLI, BTE2002-04670 (Ministerio de Ciencia y Tecnología) and SA088/04 (Junta de Castilla y León) supported this study.Peer reviewe

Coccolithophore calcification is independent of carbonate chemistry in the tropical ocean

Marañón, Emilio ... et al.-- 13 pages, 7 figures, 1 table, supporting information https://dx.doi.org/10.1002/lno.10295Short-term experiments indicate that seawater acidification can cause a decrease in the rate of calcification by coccolithophores, but the relationship between carbonate chemistry and coccolithophore calcification rate in natural assemblages is still unclear. During the Malaspina 2010 circumnavigation, we measured primary production, calcification, coccolithophore abundance, particulate inorganic carbon (PIC) concentration, and the parameters of the carbonate system, along basin-scale transects in the tropical Atlantic, Indian and Pacific oceans. Euphotic layer-integrated calcification and mean cell-specific calcification in the euphotic layer ranged between 2–10 mgC m−2 d−1 and 5–20 pgC cell−1 d−1, respectively. We found a significant relationship between primary production and calcification, such that the calcification to primary production (CP/PP) ratio was relatively invariant among ocean basins, with an overall mean value of 0.05 ± 0.04. Extrapolating this value to the entire ocean would result in a global pelagic calcification rate of 2.4 PtC yr−1. The mean PIC concentration in surface waters was 1.8 ± 1.6 mgC m−3 and its turnover time averaged 20 d. We combined our data of calcification, primary production, and carbonate chemistry from Malaspina 2010 with those obtained during two previous cruises in the northern Arabian Sea. Both the CP/PP ratio and cell-specific calcification were largely constant across a wide range of calcite saturation state (1.5–6.5), [ inline image]/[H+] (0.08–0.24; mol: μmol), and pH (7.6–8.1), which indicates that calcification by natural coccolithophore assemblages was independent of carbonate chemistry. Our results suggest that coccolithophore calcification, at least in tropical regions, may not be decreasing in the currently acidifying oceanFunding for this study was provided by the Spanish Ministry of Science and Innovation through research projects Malaspina 2010 (grant no. CSD2008-00077), PERSEO (CTM2007-28925-E/MAR), MANIFEST (CTM2012-32017) and TERRIFIC (CTM2014-53582-R). Funding for W.M.B. came from the NSF (OCE-0961660; OCE1220068), NASA (NNX11AO72G; NNX11AL93G; NNX14AQ41G; NNX14AQ43A; NNX14AL92G; NNX14AM77G) and NOAA (NA11OAR4310055).Peer Reviewe

Wind-induced changes in the dynamics of fluorescent organic matter in the coastal NW Mediterranean

Original research paperMarine biogeochemistry dynamics in coastal marine areas is strongly influenced by episodic events such as rain, intense winds, river discharges and anthropogenic activities. We evaluated in this study the importance of these forcing events on modulating seasonal changes in the marine biogeochemistry of the northwestern coast of the Mediterranean Sea, based on data gathered from a fixed coastal sampling station in the area. A 4-year (2011–2014) monthly sampling at four depths (0.5 m, 20 m, 50 m and 80 m) was performed to examine the time variability of several oceanographic variables: seawater temperature, salinity, inorganic nutrient concentrations (NO3−, PO43 − and SiO2), chlorophyll a (Chl a), dissolved organic carbon (DOC) and fluorescent dissolved organic matter (FDOM). FDOM dynamics was predominantly influenced by upwelling events and mixing processes, driven by strong and characteristic wind episodes. SW wind episodes favored the upwelling of deeper and denser waters into the shallower shelf, providing a surplus of autochthonous humic-like material and inorganic nutrients, whereas northerlies favored the homogenization of the whole shelf water column by cooling and evaporation. These different wind-induced processes (deep water intrusion or mixing), reported along the four sampled years, determined a high interannual environmental variability in comparison with other Mediterranean sampling sites. Graphical abstract Image 1 Download : Download high-res image (344KB)Download : Download full-size imageECOSER (CTM2011-15937-E), DOREMI (CTM2012-342949), SUAVE (CTM2014/ 23456/1) and ANIMA (CTM2015-65720) from the Spanish Ministerio de Economía y Competitividad (MINECO) and the Grup de Recerca Consolidat 2014SGR1179 and 2014SGR1029 financed by the Agència de Gestió d'Ajuts Universitaris i de Recerca (AGAUR) from the Generalitat de Catalunya; (JAEPre_2011_00923) from the Agencia Estatal Consejo Su perior de Investigaciones Científicas (CSIC) and the project FERMIO (MINECO, CTM2014-57334-JIN) co-financed with FEDER fundsVersión del editor3,25

Insolation dependence of the southeastern Subtropical Pacific sea surface temperature over the last 400 kyrs

4 pages, 4 figuresThe present study describes the first sea surface temperature (SST) reconstruction in the southeastern Subtropical Pacific Ocean, offshore the South American coast. The obtained record encompasses the last 400 kyr and follows the characteristic glacial/interglacial pattern defined by global ice volume. However, SST leads the δ18O isotopic record reflecting the role of the low latitudes areas in driving climate change. SST in the Holocene is lower by about 0.5-0.8°C than maximal SST in stages 5e, 7, 9 and 11. SST in stages 2-4 is lower by about 0.6-1.3°C than minimal SST in stages 6, 8 and 10. These features are similar to SST records obtained in the South Atlantic Ocean pointing to a general inter-basinal behaviour at these low latitudes. For most of the record, the observed long-term SST evolution is well correlated with the orbital parameter of eccentricity, which modulates the insolation at low latitudes. However, at low eccentricity values (Stages 11 - 9 and Termination I), SST is driven by obliquity, exhibiting a dependence from high latitude climatic responsesFinancial support from the TEMPUS EU project (ENV4-CT97-0564) and CYCIT (ANT94-0040) is acknowledge

Evidence for Increased Reservoir Ages and Poorly Ventilated Deep Waters in the Glacial Eastern Equatorial Pacific

2014 American Geophysical Union Fall Meeting, 15-19 december 2014, San FranciscoIt has been hypothesised that a poorly ventilated deep Pacific Ocean would have contributed significantly to reduce glacial atmospheric CO2. Although radiocarbon evidence for a deglacial rise in deep Pacific ventilation so far remains conflicting, this may stem in part from surface reservoir age uncertainties and their effect on inferred deep ocean ventilation ages. Here we use chronostratigraphic calendar age constraints to estimate surface reservoir age variability, and therefore deep ventilation ages, in the Eastern Equatorial Pacific over the last 25 kyr. Both the shallow- and deep ventilation records show a deglacial decrease in glacial radiocarbon depletion, consistent with other South Pacific and Southern Ocean ventilation reconstructions where surface reservoir ages have been assessed. We propose that this basin-wide agreement can be explained by ocean interior transport pathways similar to the modern, implying significantly reduced air-sea gas exchange in the southern high latitudes during the last glacial periodPeer Reviewe

Molecular basis of ocean acidification sensitivity and adaptation in <i>Mytilus galloprovincialis</i>

Predicting the potential for species adaption to climate change is challenged by the need to identify the physiological mechanisms that underpin species vulnerability. Here, we investigated the sensitivity to ocean acidification in marine mussels during early development, and specifically the trochophore stage. Using RNA and DNA sequencing and in situ RNA hybridization, we identified developmental processes associated with abnormal development and rapid adaptation to low pH. Trochophores exposed to low pH seawater exhibited 43 differentially expressed genes. Gene annotation and in situ hybridization of differentially expressed genes point to pH sensitivity of (1) shell field development and (2) cellular stress response. Five genes within these two processes exhibited shifts in allele frequencies indicative of a potential for rapid adaptation. This case study contributes direct evidence that protecting species’ existing genetic diversity is a critical management action to facilitate species resilience to climate change

Molecular basis of ocean acidification sensitivity and adaptation in Mytilus galloprovincialis

Predicting the potential for species adaption to climate change is challenged by the need to identify the physiological mechanisms that underpin species vulnerability. Here we investigated the sensitivity to ocean acidification in marine mussels during early development, and specifically the trochophore stage. Using RNA and DNA sequencing and in situ RNA hybridization, we identified developmental processes associated with abnormal development and rapid adaptation to low pH. Trochophores exposed to low pH seawater exhibited 43 differentially expressed genes. Gene annotation and in situ hybridization of differentially expressed genes point to pH sensitivity of (1) shell field development and (2) cellular stress response. Five genes within these two processes exhibited shifts in allele frequencies indicative of a potential for rapid adaptation. This case study contributes direct evidence that protecting species' existing genetic diversity is a critical management action to facilitate species resilience to climate change

Proxy development in cold-water corals: Experimental calibrations and application to the Mediterranean Sea

Goldschmidt2019, 18-23 August 2019, BarcelonaIn paleoceanography, there is growing interest in cold-water corals as high-resolution, powerful archives of multiple variables and conditions of oceans in the past. A number of potential paleo-proxies have been explored, and so far only several field-calibrations in a few species have been developed. In this presentation we will show details and outcomes of a long-term experiment being run at the ICM (Barcelona), where live specimens (~130) of Desmophyllum dianthus collected from Comau Fjord (Chile) have been kept under controlled and manipulated variables (temperature, pH, phosphate, barium, cadmium) and feeding frequency for more than two years. With this setup, in combination with geochemical analysis of the coral skeletons using Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS), we aim to calibrate specific elemental ratios including P/Ca, Ba/Ca, Cd/Ca, B/Ca, U/Ca and Mg/Li as proxies of nutrient dynamics, pH, carbonate ion concentration and temperature, respectively. Data obtained so far from this experiment will be presented, and comparisons between experimental and field calibrations will be drawn and discussed. In parallel, we have been working lately with fossil D. dianthus corals (whole specimens and fragments) collected embedded in deep sea sediment cores from the southeast Alboran Sea, in the cold-water coral mounds from the Melilla Province (Western Mediterranean Sea). Geochemical data from these specimens encompassing the elemental ratios experimentally calibrated with the long-term experiment, in addition to U/Th dating, will be interpreted in the context of molecular biomarkers records in the same and nearby sediment cores, covering the last glacial to interglacial cycl