Seasonal contribution of living phytoplankton carbon to vertical fluxes in a coastal upwelling system (Ría de Vigo, NW Spain)

The aim of this study is to explore the contribution of living phytoplankton carbon to vertical fluxes in a coastal upwelling system as a key piece to understand the coupling between primary production in the photic layer and the transfer mechanisms of the organic material from the photic zone. Between April 2004 and January 2005, five campaigns were carried out in the Ría de Vigo (NW Iberian Peninsula) covering the most representative oceanographic conditions for this region. Measurements of particulate organic carbon (POC), chlorophyll-a (chl a), phaeopigments (phaeo), and identification of phytoplankton species were performed on the water column samples and on the organic material collected in sediment traps.The POC fluxes measured by the sediment traps presented no seasonal variation along the studied period ranging around a mean annual value of 1085±365mgm-2d-1, in the upper range of the previously reported values for other coastal systems. The fact that higher POC fluxes were registered during autumn and winter, when primary production rates were at their minimum levels points to a dominant contribution of organic carbon from resuspended sediments on the trap collected material. On the contrary, fluxes of living phytoplankton carbon (Cphyto) and chl a clearly presented a seasonal trend with maximum values during summer upwelling (546mgm-2d-1 and 22mgchl am-2d-1, respectively) and minimum values during winter (22mgm-2d-1 and 0.1mgchl am-2d-1, respectively). The contribution of Cphyto to the vertical flux of POC ranged between 2% and 49% in response to the pelagic phytoplankton community structure. Higher values of Cphyto fluxes were registered under upwelling conditions which favour the dominance of large chain-forming diatoms (Asterionellopsis glacialis and Detonula pumila) that were rapidly transferred to the sediments. By contrast, Cphyto fluxes decreased during the summer stratification associated with a pelagic phytoplankton community dominated by single-cell diatoms and flagellates. Minimal Cphyto fluxes were observed during the winter mixing conditions, when the presence of the benthic specie Paralia sulcata in the water column also points toward strong sediment resuspension.Financial support came from CICYT projectREN 2003-04458 and EU projectEVK3-19 CT-2002-00071. D.Z. is funded by a postdoctoral fellowship (Jae-Doc) from the CSIC.Peer reviewe

Influence of mussel culture on the vertical export of phytoplankton carbon in a coastal upwelling embayment (Ría de Vigo, NW Iberia)

14 páginas, 2 tablas, 8 figurasThe goal of this paper is to find out whether suspended mussel culture affects the vertical fluxes of biogenic particles in the Ría de Vigo on a seasonal scale. With this aim, vertical fluxes of particulate organic carbon (POC) and the magnitude and composition of vertical export of phytoplankton carbon (Cphyto) collected in sediment traps were examined by comparing data obtained inside a mussel farming area (RaS) with those found at a reference station (ReS) not affected by mussels. Our results indicate that mussel farming has a strong impact on sedimentation fluxes under the rafts, not only increasing POC flux but also altering the magnitude and composition of Cphyto fluxes. Average POC flux at RaS (2564 ± 1936 mg m−2 day−1) was four times higher than at ReS (731 ± 276 mg m−2 day−1), and much of this increase was due to biodeposit fluxes (Cbiodep) which accounted for large proportion of POC flux (35–60 %). Indeed, because of this high Cbiodep flux, only a small proportion of the POC flux was due to Cphyto flux (3–12 %). At the same time, we observed an increased sedimentation of phytoplankton cells at RaS that could be explained by a combination of mechanisms: less energetic hydrodynamic conditions under mussel rafts, ballast effect by sinking mussel feces, and diatom aggregates. Moreover, mussel farming also altered the quality of the Cphyto flux by removing part of the predatory pressure of zooplankton and thus matching diatom composition in water column and sediment trapsFinancial support came from MICINN RAFTING project (CTM2007-61983/MAR, CTM2007-30624-E/MAR). D. Z. was funded by a postdoctoral fellowship (Plan I2C) from Xunta de GaliciaPeer reviewe

Regulator of calcineurin 1 (Rcan1) has a protective role in brain ischemia/reperfusion injury

<p>Abstract</p> <p>Background</p> <p>An increase in intracellular calcium concentration [Ca²⁺]_iis one of the first events to take place after brain ischemia. A key [Ca²⁺]_i-regulated signaling molecule is the phosphatase calcineurin (CN), which plays important roles in the modulation of inflammatory cascades. Here, we have analyzed the role of endogenous regulator of CN 1 (Rcan1) in response to experimental ischemic stroke induced by middle cerebral artery occlusion.</p> <p>Methods</p> <p>Animals were subjected to focal cerebral ischemia with reperfusion. To assess the role of Rcan1 after stroke, we measured infarct volume after 48 h of reperfusion in <it>Rcan1 </it>knockout (KO) and wild-type (WT) mice. <it>In vitro </it>studies were performed in astrocyte-enriched cortical primary cultures subjected to 3% oxygen (hypoxia) and glucose deprivation (HGD). Adenoviral vectors were used to analyze the effect of overexpression of Rcan1-4 protein. Protein expression was examined by immunohistochemistry and immunoblotting and expression of mRNA by quantitative real-time Reverse-Transcription Polymerase Chain Reaction (real time qRT-PCR).</p> <p>Results</p> <p>Brain ischemia/reperfusion (I/R) injury <it>in vivo </it>increased mRNA and protein expression of the calcium-inducible Rcan1 isoform (Rcan1-4). I/R-inducible expression of Rcan1 protein occurred mainly in astroglial cells, and in an <it>in vitro </it>model of ischemia, HGD treatment of primary murine astrocyte cultures induced Rcan1-4 mRNA and protein expression. Exogenous Rcan1-4 overexpression inhibited production of the inflammatory marker cyclo-oxygenase 2. Mice lacking Rcan1 had higher expression of inflammation associated genes, resulting in larger infarct volumes.</p> <p>Conclusions</p> <p>Our results support a protective role for Rcan1 during the inflammatory response to stroke, and underline the importance of the glial compartment in the inflammatory reaction that takes place after ischemia. Improved understanding of non-neuronal mechanisms in ischemic injury promises novel approaches to the treatment of acute ischemic stroke.</p

Impact of atmospheric deposition on the metabolism of coastal microbial communities

11 páginas, 3 tablas, 5 figurasThe impact of rain water collected at marine, urban and rural sites on coastal phytoplankton biomass, primary production and community composition as well as the effect on microbial plankton metabolism was studied in 3 microcosm experiments conducted under contrasting spring, autumn and winter conditions. The measured responses were highly variable. Rainwater additions increased chlorophyll a (Chl a) concentration (5–68% difference between rainwater treatments relative to the control) in all experiments and reduced or stimulated primary production (PP) depending on the treatment and the experiment (from −10 to +169% relative to the control). Autotrophic stimulation was highest in spring, probably related to the low initial natural nutrient concentrations. Under winter nutrient replete conditions, rainwater inputs changed the phytoplankton community although this change did not promote increases in primary production. Enhancement of net autotrophy (increase of net oxygen production up to 227%) after rainwater inputs were only found during the period of low nutrient availability. Inputs of dissolved organic nitrogen (DON) explained a large fraction of the variability in the response of PP, Chl a, community respiration (CR) and net community production (NCP). Our results suggest that differences in the initial environmental conditions (i.e. nutrient availability), rainwater composition and the ability of the present autotrophic communities to utilize the new nutrients result in substantial changes in the microbial responses and associated biologically-mediated carbon fluxes. As atmospheric nutrient inputs into coastal oceans are increasing rapidly, our results help to understand the effects of different inputs on the metabolism of distinct microbial communitiesThis research was supported by the Galician Government (Xunta de Galicia) through the grants 07MMA002402PR (IMAN) and PGIDIT06PXIB312222PR (AddEx). S.M-G. and E.E.G-M. were funded by F.P.U. fellowships and E.T. by a Ramón y Cajal contract of the Spanish Ministry of Science and InnovationPeer reviewe

Can Physical Activity Reduce the Risk of Cognitive Decline in Apolipoprotein e4 Carriers? A Systematic Review

Physical activity (PA) reduces the risk of cognitive decline (CD) in the general population. However, little is known about whether the presence of the apolipoprotein E epsilon 4 allele (APOE e4) could modify this beneficial effect. The aim of this systematic review was to analyze and synthetize the scientific evidence related to PA levels and CD risk in cognitively healthy APOE e4 carriers. Four electronic databases were analyzed. Only original articles with longitudinal study design were selected to analyze the relationship between PA and CD in APOE e4 carriers. Five studies were included in the systematic review. All studies except one stated that PA is a protective factor against CD in APOE e4 carriers. Moreover, partial support was found for the hypothesis that a greater amount and intensity of PA are more beneficial in CD prevention. The results support the idea that PA is a protective factor against CD in APOE e4 carriers. Nevertheless, it would be necessary to carry out further studies that would allow these findings to be contrasted

CIBERER: Spanish national network for research on rare diseases: A highly productive collaborative initiative

13 páginas,1 figura, 3 tablas, 1 apéndice. Se extraen los autores pertenecientes a The CIBERER network que trabajan en Centros del CSIC del Appendix ACIBER (Center for Biomedical Network Research; Centro de Investigación Biomédica En Red) is a public national consortium created in 2006 under the umbrella of the Spanish National Institute of Health Carlos III (ISCIII). This innovative research structure comprises 11 different specific areas dedicated to the main public health priorities in the National Health System. CIBERER, the thematic area of CIBER focused on rare diseases (RDs) currently consists of 75 research groups belonging to universities, research centers, and hospitals of the entire country. CIBERER's mission is to be a center prioritizing and favoring collaboration and cooperation between biomedical and clinical research groups, with special emphasis on the aspects of genetic, molecular, biochemical, and cellular research of RDs. This research is the basis for providing new tools for the diagnosis and therapy of low-prevalence diseases, in line with the International Rare Diseases Research Consortium (IRDiRC) objectives, thus favoring translational research between the scientific environment of the laboratory and the clinical setting of health centers. In this article, we intend to review CIBERER's 15-year journey and summarize the main results obtained in terms of internationalization, scientific production, contributions toward the discovery of new therapies and novel genes associated to diseases, cooperation with patients' associations and many other topics related to RD research.This study has been funded by Instituto de Salud Carlos III (ISCIII) and Spanish Ministry of Science and InnovationPeer reviewe

Determinación de parámetros bio-ópticos del fitoplancton marino y su aplicación en modelos de producción primaria

164 páginasXunta de GaliciaProyecto europeo MAS2 CT93-0065Proyecto AMB93-0129Peer reviewe

Determination of phytoplankton absorption coefficient in natural seawater samples: evidence of a unique equation to correct the pathlength amplification on glass-fiber filters

12 pages, 7 figures, 4 tables.Estimations of the spectral absorption coefficients of phytoplankton in the sea, based on the spectrum of absorption of particles retained on a filter, require a correction for pathlength amplification in the glass fibre filter (beta factor). The relationship between the optical density in suspension and 'on filter' is misleading due to the hysteresis effect. This effect is reduced on eliminating the absorption due to non-pigmentary material, minimising the dependency of the beta factor on wavelength. A general quadratic equation, ODsus(lambda) = 0.38ODfilter(lambda) + 0.42OD2filter(lambda) (r2 = 0.97, n = 15600), was obtained on comparing 52 pairs of spectra of 9 marine phytoplankton species. The algorithm was validated against natural samples, obtaining a 1% average error. Comparisons between Cleveland & Weidemann's equation (1993, Limnol Oceanogr 38:1321-1327) and the equation obtained in this study provided a 2% average difference, suggesting that a unique equation can be useful in determining the phytoplankton absorption coefficient in seawater samples. We compared the absorption coefficients obtained by spectra reconstructed from the pigment content in seawater samples with those obtained with spectra on GF/F filters and beta-corrected. Our results indicate that the spectra-reconstructed approach is only suitable when the sample consists of small quasi-spherical cells. For coastal-upwelling samples which are mainly composed of large cells the approach overestimates the package effect.This research was funded by ClCYT project AMB93-0129. The work of B.A. was supported by a predoctoral grant from Xunta de Galicia.Peer reviewe

Significance of nanophytoplankton photosynthesis and primary production in a coastal upwelling system (Ría de Vigo, NW Spain)

15 pages, 6 figures, 7 tables.The Rías Baixas are reported to have the highest primary production along the NW coast of Spain due to the influence of upwelling, which occurs from April to October. Samples were taken over 2 wk periods at a single station in the Ría de Vigo during spring, summer and autumn 1993 to study the variation in the phytoplankton photosynthetic parameters (light limited slope, αB and light saturated chlorophyll specific rate, PmB) and daily primary production in relation to phytoplankton size class, species and hydrographic parameters. The range in primary production for the Ría was 65 to 3689 mg C m-2 d-1 for total phytoplankton, 65 to 2833 mg C m-2 d-1 for net phytoplankton and 0 to 1650 mg C m-2 d-1 for nanophytoplankton. The data suggest that most of the variation in primary production in the Ría during the upwelling season was due to nanophytoplankton. Upwelling/downwelling cycles in the Ría therefore give rise to a larger variation in energy transfer through the microbial loop than through the classic, short, food chain. This is caused mainly by increases in nanophytoplankton αB coupled with high NO3 due to upwelling events. The data also suggest that there are 3 principal factors that give high primary production in the Ría. Periodic relaxation and stratification events linked to water column heating during upwelling/downwelling cycles coincided with periods of high productivity. Size class also influences the primary production; net phytoplankton had significantly higher primary production during the upwelling season than the nanophytoplankton and was responsible for 66% of the mean primary production. Species differences affected the primary production in the Ría; highest values coincided with blooms of Chaetoceros spp. and the lowest with dinoflagellate blooms of Gymnodinium catenatum.This work was financed partly by the Xunta de Galicia (project Xuga 40205 B 92) and by the Comision Interministerial de Ciencia y Tecnologia (CICYT; project AMB92-0165). B.A. was funded by a post graduate grant from the Xunta de Galicia. E.G.F. was supported by the Plan de Formacion de Recursos Humanos of the Oriente University, Venezuela and G.H.T by the European Commission MAST programme (MAS3-CT96-5022).Peer reviewe

Implications of bio-optical modeling of phytoplankton photosynthesis in Antarctic waters: Further evidence of no light limitation in the Bransfield Strait

10 páginas, 9 figuras, 1 tablaDuring the cruise ECOANTAR 94 photosynthesis versus irradiance relationships, phytoplankton spectral absorption, quantum yield of carbon fixation, and water column light regime were determined in the eastern Bransfield Strait and surrounding areas of the Weddell Sea and Weddell–Scotia Confluence, to determine if photosynthesis is light limited in these areas. There were no significant differences in the light-saturated chlorophyll-specific rate of photosynthesis (PBm), light-limited slope (aB), light saturation parameter (EkPAR), and the maximum quantum yield (thetam) between surface and subsurface water for several water masses in the area, which indicates that the photosyn-thetic response in the upper mixed layer was uniform. There were also no significant differences between the spectral light saturation parameter (EkPUR) and the mean absorbed irradiance by phytoplankton in the upper mixed layer (EumlPUR). These similarities suggest that phytoplankton photosynthesis was not light limited in this Antarctic region during the cruise period. This was also affirmed by the fact that the average operational quantum yield of the water column (0.03 mol C [mol photons]-1) was half of the mean maximum quantum yield (0.06 mol C [mol photons]-1). Primary production is underestimated by 24% when broadband models are compared with spectral ones. These results have important implications for the modeling of carbon flows in the Southern Ocean.This research was supported by the CICYT (Spanish Commission of Science and Technology) projects ANT93–0997 and AMB93–0129. The work of B.A. was funded by a grant from Xunta de GaliciaPeer reviewe