El deteriorament dels ecosistemes marins del Mediterrani s'accelera per l'increment de CO2

Els ecosistemes marins són la base de l'economia de molts països costaners però aquests ecosistemes són molt sensibles a canvis en l'acidificació de l'aigua. Un equip de científics experts en l'estudi dels oceans ha descobert que l'increment de temperatures pot augmentar-ne l'acidificació. L'augment del CO2 atmosfèric comporta un augment de CO2 al medi marí i un augment de temperatura per efecte hivernacle, ambdós causa d'acidificació de l'aigua. En un article publicat a Nature Climate Change, investigadors del projecte europeu MedSeA, coordinat per l'Institut de Ciència i Tecnologia Ambientals (ICTA) de la UAB, alerten d'un deteriorament molt ràpid dels ecosistemes marins costaners a causa de l'increment dels nivells de CO2 amb pèrdues importants de biodiversitat que donarien motius de preocupació a la indústria de l'aqüicultura.Los ecosistemas marinos son la base de la economía de muchos país escosteros pero estos ecosistemas son muy sensibles a cambios en la acidificación del agua. Un equipo de científicos expertos en el estudio delos océanos ha descubierto que el incremento de temperaturas puedeaumentar la acidificación. El aumento del CO atmosférico conlleva una umento de CO en el medio marino y un aumento de temperatura porefecto invernadero, ambos causantes de la acidificación del agua. En un artículo publicado en Nature Climate Change, investigadores delproyecto europeo MedSeA, coordinado por el Instituto de Ciencia yTecnología Ambientales (ICTA) de la UAB, alertan de un deterioro muy rápido de los ecosistemas marinos costeros debido al incremento de losniveles de CO con pérdidas importantes de biodiversidad que daríanmotivos de preocupación en la industria de la acuicultura

Temperature affects the morphology and calcification of Emiliania huxleyi strains

The global warming debate has sparked an unprecedented interest in temperature effects on coccolithophores. The calcification response to temperature changes reported in the literature, however, is ambiguous. The two main sources of this ambiguity are putatively differences in experimental setup and strain specificity. In this study we therefore compare three strains isolated in the North Pacific under identical experimental conditions. Three strains of Emiliania huxleyi type A were grown under non-limiting nutrient and light conditions, at 10, 15, 20 and 25 °C. All three strains displayed similar growth rate versus temperature relationships, with an optimum at 20–25 °C. Elemental production (particulate inorganic carbon (PIC), particulate organic carbon (POC), total particulate nitrogen (TPN)), coccolith mass, coccolith size, and width of the tube element cycle were positively correlated with temperature over the sub-optimum to optimum temperature range. The correlation between PIC production and coccolith mass/size supports the notion that coccolith mass can be used as a proxy for PIC production in sediment samples. Increasing PIC production was significantly positively correlated with the percentage of incomplete coccoliths in one strain only. Generally, coccoliths were heavier when PIC production was higher. This shows that incompleteness of coccoliths is not due to time shortage at high PIC production. Sub-optimal growth temperatures lead to an increase in the percentage of malformed coccoliths in a strain-specific fashion. Since in total only six strains have been tested thus far, it is presently difficult to say whether sub-optimal temperature is an important factor causing malformations in the field. The most important parameter in biogeochemical terms, the PIC : POC ratio, shows a minimum at optimum growth temperature in all investigated strains. This clarifies the ambiguous picture featuring in the literature, i.e. discrepancies between PIC : POC–temperature relationships reported in different studies using different strains and different experimental setups. In summary, global warming might cause a decline in coccolithophore's PIC contribution to the rain ratio, as well as improved fitness in some genotypes due to fewer coccolith malformations

Lluitant contra l'acidificació del Mediterrani

Patrizia Ziveri, de l'ICTA, a la UAB, coordina el projecte MedSeA que pretén estudiar l'acidificació del Mar Mediterrani provocada per l'augment de les emissions de CO2d'origen antropogènic. L'acidificació del mar pot provocar la degradació dels ecosistemes. Aquest projecte, a més de realitzar importants investigacions interdisciplinàries, intenta avisar i assessorar els governs dels països mediterranis per tal que lluitin per reduir l'emissió de CO2, i evitar així la pèrdua d'espècies en perill com el coral vermell.Patrizia Ziveri, del ICTA, en la UAB, coordina el proyecto MedSeA que pretende estudiar la acidificación del Mar Mediterráneo provocada por el aumento de las emisiones de CO2 de origen antropogénico. La acidificación del mar puede provocar la degradación de los ecosistemas. Este proyecto, además de realizar importantes investigaciones interdisciplinarias, intenta avisar y asesorar a los gobiernos de los países mediterráneos para que luchen para reducir la emisión de CO2, y evitar así la pérdida de especies en peligro como el coral rojo

2D Finite Volume Numerical Modeling of Free Surface Flows with Topography

In this thesis a finite-volume MUSCL-type scheme for the numerical solution of inhomogeneous SWE is presented. The novel aspect is data reconstruction: the scheme, named WSDGM (Weighted Surface-Depth Gradient Method), computes intercell water depths performing a weighted average of DGM and SGM reconstructions, in which the weight function depends on the local Froude number. This combination makes WSDGM capable of performing a robust tracking of wet/dry fronts and, together with an unsplit centered discretization of the bed slope source term, of exactly maintaining the static condition on non-flat topographies (C-property). Moreover, a numerical procedure performing a correction of the numerical fluxes in the computational cells with water depth smaller than a fixed tolerance enables a drastic reduction of the mass error in the presence of wetting and drying fronts. The effectiveness and robustness of the proposed scheme were assessed by comparing numerical results with the analytical and reference solutions of a set of test cases. Finally, to check the numerical model to field-scale applications, the results of two hypothetical dam-break events are reported

Temperature effects on sinking velocity of different Emiliania huxleyi strains

The sinking properties of three strains of Emiliania huxleyi in response to temperature changes were examined. We used a recently proposed approach to calculate sinking velocities from coccosphere architecture, which has the advantage to be applicable not only to culture samples, but also to field samples including fossil material. Our data show that temperature in the sub-optimal range impacts sinking velocity of E. huxleyi. This response is widespread among strains isolated in different locations and moreover comparatively predictable, as indicated by the similar slopes of the linear regressions. Sinking velocity was positively correlated to temperature as well as individual cell PIC/POC over the sub-optimum to optimum temperature range in all strains. In the context of climate change our data point to an important influence of global warming on sinking velocities. It has recently been shown that seawater acidification has no effect on sinking velocity of a Mediterranean E. huxleyi strain, while nutrient limitation seems to have a small negative effect on sinking velocity. Given that warming, acidification, and lowered nutrient availability will occur simultaneously under climate change scenarios, the question is what the net effect of different influential factors will be. For example, will the effects of warming and nutrient limitation cancel? This question cannot be answered conclusively but analyses of field samples in addition to laboratory culture studies will improve predictions because in field samples multi factor influences and even evolutionary changes are not excluded. As mentioned above, the approach of determining sinking rate followed here is applicable to field samples. Future studies could use it to analyse not only seasonal and geographic patterns but also changes in sinking velocity over geological time scales

Are research methods shaping our understanding of microplastic pollution? A literature review on the seawater and sediment bodies of the Mediterranean Sea

Altres ajuts: Acord transformatiu CRUE-CSICUnidad de excelencia María de Maeztu CEX2019-000940-MThe lack of standardization on the definition and methods in microplastic (MP) research has limited the overall interpretation and intercomparison of published data. This has presented different solutions to assess the presence of these pollutants in the natural environment, bringing the science forward. Microplastics have been reported worldwide across different biological levels and environmental compartments. In the Mediterranean Sea, numerous research efforts have been dedicated to defining the MP pollution levels. The reported MP concentrations are comparable to those found in the convergence zone of ocean gyres, pointing to this basin as one of the world's greatest plastic accumulation areas. However, to what extent are the data produced limited by the methods? Here, we present the results of a systematic review of MP research methods and occurrence targeting the seawater and sediment bodies of the Mediterranean Sea. Based on this dataset, we 1) assess the discrepancies and similarities in the methods, 2) analyze how these differences affect the reported concentrations, and 3) identify the limitations of the data produced for the Mediterranean Sea. Moreover, we reaffirm the pressing need of developing a common reporting terminology, and call for international collaboration between Mediterranean countries, especially with North African countries, to provide a complete picture of the MP pollution status in this basin

The Role of ocean acidification in Emiliania huxleyi coccolith thinning in the Mediterranean Sea

Ocean acidification is a result of the uptake of anthropogenic CO₂ from the atmosphere into the ocean and has been identified as a major environmental and economic threat. The release of several thousands of petagrams of carbon over a few hundred years will have an overwhelming effect on surface ocean carbon reservoirs. The recorded and anticipated changes in seawater carbonate chemistry will presumably affect global oceanic carbonate production. Coccolithophores as the primary calcifying phytoplankton group, and especially Emiliania huxleyi as the most abundant species have shown a reduction of calcification at increased CO₂ concentrations for the majority of strains tested in culture experiments. A reduction of calcification is associated with a decrease in coccolith weight. However, the effect in monoclonal cultures is relatively small compared to the strong variability displayed in natural E. huxleyi communities, as these are a mix of genetically and sometimes morphologically distinct types. Average coccolith weight is likely influenced by the variability in seawater carbonate chemistry in different parts of the world's oceans and on glacial/interglacial time scales due to both physiological effects and morphotype selectivity. An effect of the ongoing ocean acidification on E. huxleyi calcification has so far not been documented in situ. Here, we analyze E. huxleyi coccolith weight from the NW Mediterranean Sea in a 12-year sediment trap series, and surface sediment and sediment core samples using an automated recognition and analyzing software. Our findings clearly show (1) a continuous decrease in the average coccolith weight of E. huxleyi from 1993 to 2005, reaching levels below pre-industrial (Holocene) and industrial (20th century) values recorded in the sedimentary record and (2) seasonal variability in coccolith weight that is linked to the coccolithophore productivity. The observed long-term decrease in coccolith weight is most likely a result of the changes in the surface ocean carbonate system. Our results provide the first indications of an in situ impact of ocean acidification on coccolithophore weight in a natural E. huxleyi population, even in the highly alkaline Mediterranean Sea