Ecosistemes marins i costaners

28 pages, 5 figuesLa Mediterrània és una mar semitancada i que pateix una gran pressió a causa de l’activitat humana vora la costa, dos aspectes que la fan especialment vulnerable al canvi climàtic. Les observacions pluridecennals mostren que la mar catalana s’està escalfant a una velocitat de 0,3ºC per decenni i que el nivell del mar augmenta gairebé quatre centímetres per decenni, i els models apunten que gairebé la meitat d’aquests canvis han estat causats per l’escalfament global d’origen antropogènic. Aquests canvis progressius, juntament amb episodis puntuals de sobreescalfament a l’estiu o amb un augment de les tempestes de tardor, tenen efectes en els ecosistemes marins. Les comunitats de coral·ligen dels fons litorals, formades sobretot per organismes sèssils i de creixement lent, experimenten episodis de mortaldats massives dels quals els costa molt recuperar-se. L’extensió dels alguers de Posidonia és sensible a la temperatura i a les variacions del nivell del mar. A l’ecosistema pelàgic, els models preveuen un increment de la producció primària bruta del fitoplàncton que no es veu reflectida en un augment de la productivitat planctònica neta perquè també s’incrementa la respiració. Tant entre els organismes sèssils com en els que es poden moure (vàgils), s’observa un desplaçament cap al nord d’algunes espècies habituals al litoral català, mentre que la presència d’espècies termòfiles vingudes de més al sud augmenta. Els hiverns suaus, la poca pluviositat i els estius càlids afavoreixen els eixams de meduses a les platges. A més, algunes algues tòxiques es poden veure afavorides per aigües més càlides i més estratificades. Alguns d’aquests canvis constitueixen amenaces per als serveis de què els ecosistemes marins proveeixen la societat: referents culturals, recursos econòmics directes (turisme i pesca), protecció pel que fa a l’erosió, la captura i l’emmagatzemament de CO2 atmosfèric, o l’aprofitament farmacèutic i industrial de la riquesa genètica i metabòlica. Malauradament, els agents climàtics actuen sinèrgicament i en la mateixa direcció que molts altres agents antròpics. Recomanem, doncs, que els esforços de mitigació de l’escalfament global vagin acompanyats d’esforços de millora i de regulació d’activitats d’impacte ambiental com ho són algunes arts de pesca, la pol·lució, l’explotació recreativa o la construcció. Es fa imprescindible, també, dissenyar i aplicar estratègies d’inversió en recerca i monitoratge i en protecció d’hàbitats singularsPeer Reviewe

Acidificación oceánica: una visión a través de paleoreconstrucciones

Ponencia presentada en: VI Congreso Internacional de la Asociación Española de Climatología celebrado en Tarragona del 8 al 11 de octubre de 2008.[ES]Una buena parte del CO2 emitido a la atmósfera por las actividades humanas está siendo absorbido por los océanos, provocando su progresiva acidificación, con consecuencias nocivas para los organismos marinos, sobretodo para aquellos que construyen un esqueleto de carbonato de calcio. Para entender mejor la magnitud de este problema medioambiental, es necesario conocer como ha oscilado el pH marino en el pasado, a diferentes escalas de tiempo y en diferentes localidades. Dado que los registros instrumentales de pH existentes son muy recientes y escasos, los pH pretéritos deben reconstruirse a partir de indicadores indirectos (proxies) de archivos adecuados. Un proxy geoquímico muy prometedor es la composición isotópica de boro en fósiles biogénicos de carbonato que, de hecho, representa el único método práctico para determinar, de manera cuantitativa, las variaciones de pH marino en el pasado. En esta comunicación presentamos y discutimos la base teórica de este proxy y algunas de las reconstrucciones de paleo-pH publicadas hasta el momento.[EN]A large part of CO2 emitted by human activities in the atmosphere is being absorbed by the oceans, leading to a progressive acidification, with detrimental effects on marine organisms, particularly those that build a skeleton of calcium carbonate. To better understand the magnitude of this environmental problem, it is necessary to know how seawater pH has oscillated in the past, at different timescales and locations. Because instrumental records of seawater pH exceeding a couple of decades are not yet available, past variations of pH need to be reconstructed using indirect indicators or proxies in suitable archives. A very promising geochemical proxy is the isotopic composition of boron in fossil biogenic carbonates which is, so far, the only practical method to quantitatively determine seawater pH variations back through time. In this communication, we present and discuss the theoretical grounds of this proxy and some of the paleo-pH reconstructions published so far.Este trabajo forma parte del proyecto ROMIAT (CTM2006-01957/MAR), financiado por el Ministerio de Educación y Ciencia, y es una de las actividades del Grup de Recerca en Biogeoquímica Marina i Canvi Global (2005SGR00021), financiado por la Generalitat de Catalunya. E.C. agradece un contrato Ramón y Cajal

Copepod performance under CO2-induced acidification: the case of Acartia grani and Oithona davisae

11th Panhellenic Symposium on Oceanography and Fisheries, Aquatic Horizons : Challenges & Perspectives, 13-17 May 2015, Mytilene, Lesvos island, Greece.-- 11ο Πανελλήνιο Συμπόσιο Ωκεανογραφίας & Αλιείας, Μυτιλήνη, Λέσβος, Ελλάδα.-- 4 pagesThis experimental study aimed to evaluate the direct impact of two distinct pH levels, one “Control” (pHNBS: 8.17) and one “Low pH” (pHNBS: 7.75) on the feeding, respiration and reproductive output of two marine copepods: the calanoid Acartia graniand the cyclopoid Oithonadavisae. Adult copepods collected from laboratory cultures were preconditioned for 4 consecutive days at a dinoflagellate suspension (Akashiwo sanguinea) prepared with filtered sea water preadjusted at the targeted pH values via CO2 bubbling. Water acidification had no direct effect on the examined vital rates for any of the two copepod species. Our results lend support to the generally observed lack of direct influence of the seawater pH decrease projected at the end of the century on the group of copepodsThis work was supported by the project CROA (LS8-1893), implemented within the framework of the «Supporting Postdoctoral Researchers» Action of the >Education and Lifelong Learning> Operational Program (Action’s Beneficiary: General Secretariat for Research and Technology), and was cofinanced by the European Social Fund (ESF) and the Greek StatePeer Reviewe

Increased reservoir ages and poorly ventilated deep waters inferred in the glacial Eastern Equatorial Pacific

Consistent evidence for a poorly ventilated deep Pacific Ocean that could have released its radiocarbon-depleted carbon stock to the atmosphere during the last deglaciation has long been sought. Such evidence remains lacking, in part due to a paucity of surface reservoir age reconstructions required for accurate deep-ocean ventilation age estimates. Here we combine new radiocarbon data from the Eastern Equatorial Pacific (EEP) with chronostratigraphic calendar age constraints to estimate shallow sub-surface reservoir age variability, and thus provide estimates of deep-ocean ventilation ages. Both shallow- and deep-water ventilation ages drop across the last deglaciation, consistent with similar reconstructions from the South Pacific and Southern Ocean. The observed regional fingerprint linking the Southern Ocean and the EEP is consistent with a dominant southern source for EEP thermocline waters and suggests relatively invariant ocean interior transport pathways but significantly reduced air–sea gas exchange in the glacial southern high latitudes

Increased reservoir ages and poorly ventilated deep waters inferred in the glacial Eastern Equatorial Pacific.

Consistent evidence for a poorly ventilated deep Pacific Ocean that could have released its radiocarbon-depleted carbon stock to the atmosphere during the last deglaciation has long been sought. Such evidence remains lacking, in part due to a paucity of surface reservoir age reconstructions required for accurate deep-ocean ventilation age estimates. Here we combine new radiocarbon data from the Eastern Equatorial Pacific (EEP) with chronostratigraphic calendar age constraints to estimate shallow sub-surface reservoir age variability, and thus provide estimates of deep-ocean ventilation ages. Both shallow- and deep-water ventilation ages drop across the last deglaciation, consistent with similar reconstructions from the South Pacific and Southern Ocean. The observed regional fingerprint linking the Southern Ocean and the EEP is consistent with a dominant southern source for EEP thermocline waters and suggests relatively invariant ocean interior transport pathways but significantly reduced air-sea gas exchange in the glacial southern high latitudes.We acknowledge funding by the Spanish Ministry of Economy and Competitiveness through grants CTM2009-08849 (ACDC Project) and CTM2012-32017 (MANIFEST Project). M. de la Fuente was funded by a FPI studentship (BES-2010-039700) from the Spanish Government, and L. Skinner acknowledges support from NERC grant NE/L006421/1.This is the final version. It first appeared at http://www.nature.com/ncomms/2015/150703/ncomms8420/full/ncomms8420.html

Interdcadal climate variability in the Coral Sea since 1708 A.D.

Low resolution (5-year) Sr/Ca and δ18O samples, extending back to 1708 A.D., were analysed from a Porites coral core collected from Flinders Reef, an offshore reef on the Queensland Plateau in the western Coral Sea (17.5° S, 148.3° E). Using the Sr/C

Identification and removal of Mn-Mg-rich contaminant phases in foraminiferal tests: Implications for Mg/Ca past temperature reconstructions

The geochemical composition of foraminifera shells from an Ocean Drilling Program site in the Panama Basin has been analyzed by several analytical techniques (LA-ICP-MS, ICP-MS, XRD, SEM, EDX) in order to identify and evaluate the occurrence of contaminant phases which may bias paleoenvironmental reconstructions. LA-ICP-MS results on uncleaned tests indicate the presence of Mn-Mg-rich contaminant phases at the inner surfaces of the foraminiferal shells (which have Mn/Ca ratios up to 400 mmol mol-1 and Mg/Ca ratios up to 50 mmol mol-1). We have rigorously assessed the ability of different cleaning protocols to remove these contaminant phases and have obtained satisfactory results only when a reductive step is included. The analysis of cleaning residuals collected after each of the different cleaning steps applied reveals that high Mn values are associated with at least two different contaminant phases, of which only one is linked to high Mg values. XRD analysis further reveals that the Mn-Mg-rich phase is the Ca-Mn-Mg carbonate kutnahorite (Ca(Mn, Mg)(CO3)2). Our results demonstrate that the presence of kutnahorite-like minerals can bias Mg/Ca ratios toward higher values (by 7-36%) and lead to significant overestimation of past seawater temperatures (by 0.9 up to 6.2°C, in the case of these Panama Basin samples)

Increased reservoir ages and poorly ventilated deep waters inferred in the glacial Eastern Equatorial Pacific.

Consistent evidence for a poorly ventilated deep Pacific Ocean that could have released its radiocarbon-depleted carbon stock to the atmosphere during the last deglaciation has long been sought. Such evidence remains lacking, in part due to a paucity of surface reservoir age reconstructions required for accurate deep-ocean ventilation age estimates. Here we combine new radiocarbon data from the Eastern Equatorial Pacific (EEP) with chronostratigraphic calendar age constraints to estimate shallow sub-surface reservoir age variability, and thus provide estimates of deep-ocean ventilation ages. Both shallow- and deep-water ventilation ages drop across the last deglaciation, consistent with similar reconstructions from the South Pacific and Southern Ocean. The observed regional fingerprint linking the Southern Ocean and the EEP is consistent with a dominant southern source for EEP thermocline waters and suggests relatively invariant ocean interior transport pathways but significantly reduced air-sea gas exchange in the glacial southern high latitudes

Calcification reduction and recovery in native and non-native Mediterranean corals in response to ocean acidification

10 páginas, 7 figuras, 2 tablas.In recent years, some of the ramifications of the ocean acidification problematic derived from the anthropogenic rising of atmospheric CO2 have been widely studied. In particular, the potential effects of a lowering pH on tropical coral reefs have received special attention. However, only a few studies have focused on testing the effects of ocean acidification in corals from the Mediterranean Sea, despite the fact that this basin is especially sensitive to increasing atmospheric CO2. In this context, we investigated the response to ocean acidification of the two zooxanthellate coral species capable of constituting the main framework of the community, the endemic Cladocora caespitosa and the non-native Oculina patagonica. To this end, we examined the response of both species to pCO2 concentrations expected by the end of the century, 800 ppm, vs the present levels. Calcification rate measurements after 92 days of exposure to low pH conditions showed the same negative response in both species, a decrease of 32–35% compared to corals reared under control conditions. In addition, we detected in both species a correlation between the calcification rate of colonies in control conditions and the degree of impairment of the same colonies at low pH. Independent of species, faster growing colonies were more affected by decreased pH. After this period of decreased pH, we conducted a recovery experiment, in which corals reared in the acidic treatment were brought back to control conditions. In this case, normal calcification rates were reached in both species. Overall, our results suggest that O. patagonica and C. caespitosa will both be affected detrimentally by progressive ocean acidification in the near future. They do not display differences in response between native and non-native species but do manifest differential responses depending on calcification rate, pointing to a role of the coral genetics in determining the response of corals to ocean acidification.Financial support for this study was provided by the Spanish Ministry of Economy and Competitiveness through projects CTM2006-01957/MAR, CTM2009-08849/MAR, CGL2010-18466 and a FPI studentship (BES-2007-16537) to J.M. This work is a contribution from the Marine Biogeochemistry and Global Change research group, funded by Generalitat de Catalunya (Catalan Government) through grant 2009SGR142. [RH]Peer reviewe