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2nd Meeting of the Iberian Ecological Society (SIBECOL), XXI conference of the Iberian Association of Limnology (AIL) and 21st National Congress of the Portuguese Ecological Society (SPECO), 3-8 July 2022, Aveiro, Acidic polysaccharides released by phytoplankton and prokaryotic heterotrophs promote the formation of gel-like transparent exopolymer particles (TEPs). TEPs play a key role in the biological carbon pump due to their carbon-rich composition and their ability to coagulate and sink towards the deep ocean. Yet, very little is known about TEP distribution, export, and turnover at a global scale, particularly at deep ocean depths. We provide the first inventory of TEP from the surface up to 4000 m depth in the Atlantic, Indian, and Pacific Oceans and have assessed their contribution to carbon export into the deep ocean. Primary production determines TEP concentration above the deep chlorophyll maximum, and prokaryotic biomass also contributes in deeper waters. In the deep ocean waters, TEP concentrations are lower and mirror the concentrations in the surface, evidencing the importance of TEP sinking both at the export depth (200 m) with a global value of 2.9 Pg C year-1 and at the sequestration depth (1000 m) of 0.9 Pg C year-1 of particulate carbon. However, incubation experiments across ocean basins depicted rapid TEP turnover rates of 71 and 333 days (on average) within the export and sequestration depths, respectively. These findings reveal that the export of carbon by TEP sinking towards deep oceans escapes from long-term paths of the global carbon cycle

Ocean Sciences Meeting (OSM), 16-21 February 2020, San Diego, CA, USA, Eplipelagic primary production determines the flux of carbon to microbes in the bathypelagic ocean, yet whether variations in surface phytoplankton communities control the assembly of deep-sea prokaryotes remains unexplored. Here we compare the taxonomic structure of free-living and particle-attached prokaryotic communities from 4000 m with surface phytoplankton assemblages across eight stations from the Atlantic, Pacific and Indian oceans. We show that bathypelagic prokaryotic communities mirror abundance variations in surface planktonic groups such as dinoflagellates and ciliates as well as gradients in surface primary productivity, but are less influenced by the bathypelagic physicochemical environment. The similarity between surface and bathypelagic prokaryotic communities increases towards productive surface waters likely due to intense particle-driven prokaryotic transport, resulting in particle-attached bathypelagic communities similar to those in surface waters, but we also detect a pool of endemic deep-sea taxa less influenced by surface processes which are potentially chemoautotrophs. Our results suggest a key role of phytoplankton composition and activity in structuring the global bathypelagic microbiome, likely through determining the nature of sinking particles and the associated prokaryotic communities

Table S1, S2, S3, S4 and Fig. S1

The organic matter occluded in the silica of fossil diatom frustules is thought to be protected from diagenesis and used for paleoceanographic reconstructions. However, the location of the organic matter within the frustule has hitherto not been identified. Here, we combined high spatial resolution imaging by nanoSIMS and Raman micro-spectroscopy to identify where the organic material is retained in cleaned fossil diatom frustules. NanoSIMS imaging revealed that organic signals were present throughout the frustule but in higher concentrations at the pore walls. Raman measurements confirmed the heterogenous presence of organics but could not, because of lower spatial resolution, resolve the spatial patterns observed by nanoSIMS.

Association for the Sciences of Limnology and Oceanography (ASLO) Summer meeting, Water connects!, 10-15 June 2018, Victoria, Canada, Microbes comprise >90% of the biomass in the world's oceans, drive biogeochemical cycles, and have turnover rates ranging from hours to days. Despite the central role of microbes in marine systems, there is no robust way to evaluate taxon-specific mortality. Previously, we reported that there are millions of free-ribosomes per mL of seawater that are released by cell lysis, and that these can be used to estimate taxon-specific cell lysis. Here, ribosome decay and production rates were used to estimate taxon-specific microbial mortality in surface waters of the Red Sea. Free-ribosome production, indicative of cell lysis, was detected in 953 out of 1308 prokaryotic taxa after incubations with or without mitomycin C. In 261 taxa (~27%), ribosome production only occurred with mitomycin C addition, suggesting that lysis was caused by prophage induction. Overall, 60 different dynamic patterns of free-ribosomes and cells were detected across five time points in the experiment. Using the rate of ribosome production, and ribosome copy number per cell, the mortality rate of prokaryotes was estimated to average 1.3±0.64 d-1 in the controls and 2.47±0.89 d-1 in Mitomycin C treatments, and varied among taxa and treatments. Some taxa had high rates of mortality, including the genera Acinetobacter, AEGEAN-169 marine group, Phyllobacterium, Microbacterium, Halomonas and Thalassospira. Our results show high-mortality-rates are coupled to high growth rates and high relative-abundances, suggesting that r-selected have higher lysis rates. The ability to estimate taxon-specific mortality rate as the result of cell lysis adds an important tool in our quest to explain the distribution, abundance and roles of specific microbial taxa in nature

Rising temperatures in the Arctic Ocean are causing sea ice and glaciers to melt at record breaking rates, which has consequences for carbon cycling in the Arctic Ocean that are yet to be fully understood. Microbial carbon cycling is driven by internal processing of in situ produced organic carbon (OC), however recent research suggests that melt water from sea ice and glaciers could introduce an allochthonous source of OC to the microbial food web with ramifications for the metabolic balance of plankton communities. In this study, we characterized autochthonous and allochthonous sources of OC to the Western Svalbard fjord system using stable isotopes of carbon. We quantified delta C-13 of eukaryotic and prokaryotic planktonic groups using polar lipid-derived fatty acids as biomarkers in addition to measuring delta C-13 of marine particulate OC and dissolved OC from glacial runoff. delta C-13 of bacteria (-22.5&) was higher than that of glacial runoff OC (-28.5&) and other phytoplankton groups (-24.7 to -29.1&), which suggests that marine bacteria preferentially use a third source of OC. We present a Bayesian three-source delta C-13 mixing model whereby similar to 60% of bacteria carbon is derived from OC in sea ice, and the remaining carbon is derived from autochthonous production and glacial-derived OC. These results suggest that subsidies of OC from melting glaciers will not likely influence microbial carbon cycling in Svalbard fjords in the future and that further research is needed to determine the effects of melting sea ice on microbial carbon cycling in fjord systems and elsewhere in the Arctic Ocean.

European Geosciences Union General Assembly 2016 (EGU2016), 17-22 April 2016, Vienna, Austria.-- 1 page, The role of the ocean as a sink for CO2 is partially dependent on the downward transport of phytoplankton cells packaged within fast-sinking particles. However, whether such fast-sinking mechanisms deliver fresh organic carbon down to the deep bathypelagic sea and whether this mechanism is prevalent across the ocean awaits confirmation. Photosynthetic plankton, directly responsible for trapping CO2 in organic form in the surface layer, are a key constituent of the flux of sinking particles and are assumed to die and become detritus upon leaving the photic layer. Research in the 1960-70’s reported the occasional presence of well-preserved phytoplankton cells in the deep ocean, but these observations, which could signal at rapid sinking rates, were considered anecdotal. Using new developments we tested the presence of healthy phytoplankton cells in the deep sea (2000 to 4000 m depth) along the Malaspina 2010 Circumnavigation Expedition, a global expedition sampling the bathypelagic zone of the Atlantic, Indian and Pacific Oceans. In particular, we used a new microplankton sampling device, the Bottle-Net, 16S rDNA sequences, flow cytometric counts, vital stains and experiments to explore the abundance and health status of photosynthetic plankton cells between 2,000 and 4,000 m depth along the Circumnavigation track. We described the community of microplankton (> 20 μ m) found at the deep ocean (2000-4000 m depth), surprisingly dominated by phytoplankton, and within this, by diatoms. Moreover, we report the ubiquitous presence of healthy photosynthetic cells, dominated by diatoms, down to 4,000 m in the deep dark sea. Decay experiments with surface phytoplankton suggested that the large proportion (18%) of healthy photosynthetic cells observed, on average, in the dark ocean, requires transport times from few days to few weeks, corresponding to sinking rates of 124 to 732 m d-1, comparable to those of fast sinking aggregates and faecal pellets. These results confirm the expectation that fast-sinking mechanisms inject fresh organic carbon into the deep-sea and that this is a prevalent process operating across the global oligotrophic ocean

Society of Environmental Toxicology and Chemistry (SETAC) Europe 25th Annual Meeting, 3-7 May 2015, Barcelona.-- 2 pages, 4 figures, Prochlorococcus is the smallest and most abundant photosynthetic organism known on Earth and a major contributor of ocenic primary production. This cianobacterium is ubiquist in every ocean from 40°N to 40°S, from surface to 200 m depth in the water column, reaching abundances close to 10 cells/mL worldwide [1]. Its large surface/volume ratio gives it a high efficiency for light and nutrients capture. On the other hand, this characteristics also implicate a higher intake and a faster bioconcentration of pollutants, resulting in an extreme sensitivity to a variety of environmental stressors, from UV radiation to organic pollutants [2]. Therefore, Prochlorococcus constitutes an excellent sentinel organism to evaluate the dependence of the photosynthetic function to environmental variables and anthropogenic impacts in middle latitudinal oceans. Over the past century the global phytoplankton concentration has declined and changes in chlorophyll and primary production have been detected, which has been attributed to the impact of global climate change [3]. Global Change is a set of interlinked vectors, being one of the best studied the climate change. Neverthelees, the only vector whose global impact has not been quantifyed yet is chemical pollution [4]. In this way, the main objective of the present work was to measure the photosynthetic capacity of Prochlorococcus in Atlantic, Indian and Pacific oceans during the Malaspina circumnavigation, and study its relationship with the concentrations of diverse organic pollutants. This study was performed within a framework of more than 300 biological, physical and chemical variables, using both field sample collection and experiments on board with wild communities, This work was funded by the Spanish Government through the Malaspina project. MC Fernández-Pinos acknowledges a predoctoral fellowship from the Spanish National Research Council

Aquatic Sciences Meeting (Aquatic Sciences: Global And Regional Perspectives - North Meets South), 22-27 February 2015, Granada, Spain., Phytoplankton size is a property of marine ecosystems: physiological features, ecological function ¿metabolic rates, light and nutrients dependence, sinking,trophic organization, etc) are directly related to the size structure of phytoplankton assemblages. The size-abundance spectrum is a useful tool for the analysis of theese features. This model is usually expresed as alinear plot with abundances distributed ian a octave scale of cell sizes: the intercept seems to be related to total phytoplankton biomass, whereas the slope is an indicator of the biomass-share among size classes and might be related to the energy transfer efficiency along the spectrum and the phytoplankton productivity, eventually with flatter slopes in productive, high biomass phytoplankton regions and the opossite in oligotrophic ecosystems. Howevwer, our present results in the oligotrphic Atlantoc Ocean do no support this paradigm, showing no dependence of slope on the whole biomass. High biomass, steep slopes are found and their implication on the energy flow throughout the size spectrum are discussed.

Trabajo presentado en la ASLO Aquatic Science Metting, celebrada en Granada, España, del 22 al 27 de febrero de 2015

Aquatic Sciences Meeting (Aquatic Sciences: Global And Regional Perspectives - North Meets South), 22-27 February 2015, Granada, Spain., Picoplankton are the most abundant organisms in the ocean, often dominate planktonic biomass and primary production, and they could represent a substantial contribution to the global export of carbon. Today, we have a limited understanding about the factors that control the picoplankton community structure. A recent analysis indicates that light and temperature are the main factors explaining Prochlorococcus and Synechococcus distributions, whereas nutrient concentrations play a minor role (Flombaum et al., PNAS 2013). Methodological difficulties to quantify mixing in the field have motivated the use of indirect approaches to determine the input of nutrients into the euphotic zone and moreover, nutrient concentrations are not necessarily a proxy of nutrient supply. We present a large data set, including open ocean and coastal regions, of simultaneous measurements of picoplankton abundance, temperature and irradiance, together with estimates of nutrient supply. The transport of nutrients across the nutricline was computed combining nutrient concentrations and small-scale turbulence observations collected with a microstructure profiler. Our preliminary results indicate that nutrient supply also plays a role in the distribution of picoplankton functional groups in the ocean

Aquatic Sciences Meeting, Aquatic Sciences: Global And Regional Perspectives - North Meets South, 22-27 February 2015, Granada, Spain, Ocean acidification and warming are two main consequences of climate change that can directly affect organismal and ecosystem processes in marine ecosystems. This is especially true in the Arctic Ocean where temperatures are increasing 2-3 times the global rate and inherent cold temperatures and recent ice cover loss increases its vulnerability to ocean acidification. We carried out a microcosm experiment with a plankton community collected from a high Arctic Fjord (Isfjorden, Svalbard Islands) to analyze how the interaction between acidification (changes in pH, by bubbling CO2) and warming (1°C, 6°C and 10°C) could affect bacterial, protists and viral processes as bacterial production (BP), bacterial mortality by protists and viruses, and lytic vs lysogenic (LysoVP) viral production. We obtained that a 48% and a 79% of BP variability is explained by pH at 6° C and at 10°C, respectively, while at 1ºC pH also explicated a 49% variability of the percentage of bacterial removed by protists. Furthermore, pH were responsible of 86% of LysoVP and 94% of the percentage of LysoVP variability, at 10°C. However no pattern for lytic viral production and lysed bacteria were observed with pH at different temperatures. Consequently, pH together with temperature contributes to modify BP, grazing by predators, and to introduce changes in the virus cycle infection promoting LysoVP at low pH and at high temperature. This experiment provides hints to how these altered microbial processes could intervene with the carbon cycle in the Arctic Ocean

Aquatic Sciences Meeting (Aquatic Sciences: Global And Regional Perspectives - North Meets South), 22-27 February 2015, Granada, Spain., The oligotrophic subtropical gyres represent with 70 percent of the ocean surface, the largest biome on Earth, where picoplankton represent the dominant autotrophs. Predicting the response of autotrophic picoplankton to warming in the subtropical ocean is, therefore, of major consequence for biogeochemical and ecological processes in the ocean. The trend for autotrophic picoplankton to increase with temperature in the ocean has lead to predictions that autotrophic picoplankton will increase with warming, in contrast with the documented trend towards a decline in autotroph biomass and production with warming and the associated stratification in the subtropical ocean. Here we show that warming and oligotrophication, with the associated increase in photosynthetic active radiation and UV-B radiation at depth, are expected to result in a decline by 18 to 42 percent in the abundance of autotrophic picoplankton, but an increase as the dominant component of the autotrophic community in the subtropical ocean. Our study is based in the large data set compiled during the Malaspina 2010 expedition, across the Atlantic, Indian and Pacific Oceans

Aquatic Sciences Meeting, Aquatic Sciences: Global And Regional Perspectives - North Meets South, 22-27 February 2015, Granada, Spain, The cyanobacterium Prochlorococcus is the smallest and most abundant photosynthetic organism on Earth [1]. Being a main global primary producer and ubiquist in the tropical and subtropical regions of the world’s oceans [2], it constitutes a good sentinel species for evaluating the effect of environmental stressors on oceanic photosynthesis. We developed a sensitive method to monitor the expression of two genes responsible of photosynthesis in Prochlorococcus, rbcL (RuBisCO) and psbA (D1 protein), using rnpB as reference gene [3,4]. We applied the method to samples from 63 stations of the Malaspina circumnavigation cruise (December 2010 - July 2011), sampled at three depths. In addition, natural communities of nano-and picoplankton were experimentally exposed to organic pollutant mixtures. Expression of Prochlorococcus rbcL and psbA genes correlated with several physical variables and other biological measurements, and were sensitive to low levels of organic pollutant mixtures. We consider these sublethal effects on the photosynthesis, together with already known effects at cellular level [5,6], are significant potential perturbators of the oceanic carbon cycle. This confirms the anthropogenic chemosphere as a vector of global change during the Anthropocene. 1. Bryant DA 2003 Proc Natl Acad Sci USA 100:9647-9649 2. Partensky F et al. 1999 Microbiol Mol Biol Rev 63:106-127 3. Martiny AC et al. 2006 Proc Natl Acad Sci USA 103:12552-12557 4. Gomez-Baena G et al 2009 Res Microbiol 160:567-575 5. Echeveste P et al. 2010 Chemosphere 81:161-168 6. Echeveste P et al. 2011 Environ Pollut 159:1307-1316

Aquatic Sciences Meeting (Aquatic Sciences: Global And Regional Perspectives - North Meets South), 22-27 February 2015, Granada, Spain., Physical-biological coupling in pelagic ecosystems at macroscale level provide a way to understand the variability of ecological processes at global scale. In the context of the Malaspina Expedition, the vertical distribution of phytoplankton was determined using flow citometry along a cruise between Santo Domingo and Vigo on board R/V Sarmiento de Gamboa The distribution of four phytoplanktonic groups (Synechococcus, Eukaryotic picoplankton, ultraplankton and large nanoplankton) followed the main chlorophyll a pattern along the transect, whereas Prochlorococcus showed a more ubiquitous distribution. The main phytoplanton distribution pattern was determined by the presence of three biogeographic provinces well differentiated both from the nutritional status and the physical-chemical characteristics of the water column. Phytoplankton generally showed a scarce representation in the more oligotrophic waters of the North Atlantic Tropical Gyre, where Prochlorococcus constituted the the main group , with maximum,densities of 5.1x104 cells/ml. On the other hand, the rest of pico and nanoplanktonic groups reached the higher abundances in the colder and nutrient richer waters of the North Atlantic Subtropical (West Gyre and East Gyre), with peaks of 1.1x105 Synechococcus/ml and 4x104 picoeukaryotes/ml.

49th European Marine Biology Symposium (49TH EMBS), 7-12 september 2014, S. Petersburg, Russia.-- 1 page, The transfer of matter and energy from autotrophs to upper consumers in the Southern Ocean is essentially controlled by two groups of zooplankton, krill and salps. While krill (mainly Euphausia superba) is almost the unique food source for Antarctic fish, birds and mammals, salps (Salpa thompsoni) are of very indifferent nutritious value. Salps play a role at least as important as krill in the carbon cycle, filtering and packing biogenic carbon into larger and heavier faecal pellets than krill, thus accelerating the vertical flux of matter towards the long-lived and even sequestered carbon pools. Both groups show huge temporal and spatial fluctuations, with the irregular alternation of krill-dominated and salp-dominated years when salps, owing to their high rates of population growth and short life cycles dominate Antarctic zooplankton. At the same time, the continuous decreasing trend of krill populations along the last forty years has lead to predict a shift in Antarctic ecosystems, with the global substitution of krill by salps. The drivers of the change are not clear, but warmer temperatures, the extension of sea ice, and the decimation of whales appear as the most probable sources. Another consequence of the high warming rates in some Antarctic areas (i.e., the Antarctic Peninsula) would be the reduction of the individual biomass spectrum. Under these conditions, not only the populations depending of krill as food source will be severely threated, but the removal rates and fate of biogenic carbon, as well as the regeneration rates of nutrients by zooplankton excretion would change. With the objective of ascertaining the possible consequences for the cycling of biogenic carbon and the stoichiometry of regenerated nutrients of the predicted shifts in the Southern Ocean zooplankton we estimated the metabolic carbon requirements and inorganic N and P excretion rates of three major zooplankton groups in the Southern Ocean in the vicinity of the Antarctic Peninsula in February 2009. The carbon respiratory demands and NH4-N and PO4-P excretion rates of < 5 mm size copepods, krill (adult E. superba and E. crystalloropias and furcilia spp) and salps (blastozoids of Salpa thompsoni) were estimated by incubation experiments. The carbon-specific metabolic rates and N:P metabolic quotients of salps were higher than those of krill (furcilia spp. and adults) and copepods. There was also a negative relation between average individual zooplankton biomass and their metabolic rates, each metabolic process showing a particular response that leaded to different metabolic N:P ratios as a function of individual biomass. The predicted community shifts from krill to salps and the decrease of individual biomass in the Southern Ocean would therefore encompass not only the substitution of a pivotal group of Antarctic food webs (krill) by one of low nutritive value (salps). In a zooplankton community dominated by salps and of reduced individual size (biomass) there will be an increase of the zooplankton metabolic carbon demand and therefore of the proportion of primary production that should be allocated to compensate for the global zooplankton respiratory C-losses. At the same time, the production by salps of larger, faster sinking faecal pellets will increase the sequestration rate of biogenic carbon. Regarding the changes in excretion rates and N:P stoichiometry of the metabolic products by zooplankton, the characteristics of the dissolved nutrient pool could be modified, accelerating the changes on the functional and structural properties of primary producers (i.e., from diatoms to haptophytes) that would accelerate the change for the whole Antarctic ecosystem., This work was supported by the Spanish projects from the Ministry of Science and Innovation POL2006-0550/CTM to C. Duarte, CTM2006-12344-C01 to M. Alcaraz and CTM2007-60052 to E. Saiz

In this study we report the response of net community production (NCP) of plankton communities in the Arctic surface waters exposure to natural ultraviolet radiation (UVR) conditions. A possible bias in previous measurements performed using borosilicate glass bottles (opaque to most UVR) can underestimate NCP. Here we show that 77% of the sampled communities suffer, on average, 38.5% of net increase in NCP when exposed to natural UV-B condition, relative to values when UV-B radiation is excluded. UV-B tends to shift communities toward autotrophy, with the most autotrophic communities responding the strongest. This is likely explained by the inhibition of bacterial respiration during the continuous day period of the Arctic summer, corroborated by experiments where bacterial production influenced by UV-B directly affect NCP. Whereas Arctic warming is expected to lead to lower NCP, our results show that increased UV-B radiation may partially compensate this negative effect in surface waters. ©2014. American Geophysical Union., This research is a contribution to projects ARCTICMET and ATOS, funded by the Spanish Ministry of Economy and Competitiveness (CTM2011-15792-E and POL2006-00550/CTM, respectively), the ATP project funded by the FP-7 of the EU (CTM2009-07781-E) and the CarbonRidge project funded by the Norwegian Research Council. L.S.G.-C. was funded by a JAE-Predoc Malaspina fellowship (CSIC-FBBVA, Spain)

Integrated Marine Biogeochemistry and Ecosystem Research Open Science Conference (IMBER OSC 2014), Future Oceans, Research for marine sustainability: multiple stressors, drivers, challenges and solutions, 23-27 June 2014, Bergen, Norway, This study was supported by the projects ATOS, ATP and TOP-COP from the Spanish MICINN

The net plankton community metabolism of oceanic surface waters is particularly important as it more directly affects the partial pressure of CO2 in surface waters and thus the air-sea fluxes of CO2. Plankton communities in surface waters are exposed to high irradiance that includes significant ultraviolet blue (UVB, 280-315 nm) radiation. UVB radiation affects both photosynthetic and respiration rates, increase plankton mortality rates, and other metabolic and chemical processes. Here we test the sensitivity of net community production (NCP) to UVB of planktonic communities in surface waters across contrasting regions of the ocean. We observed here that UVB radiation affects net plankton community production at the ocean surface, imposing a shift in NCP by, on average, 50% relative to the values measured when excluding partly UVB. Our results show that under full solar radiation, the metabolic balance shows the prevalence of net heterotrophic community production. The demonstration of an important effect of UVB radiation on NCP in surface waters presented here is of particular relevance in relation to the increased UVB radiation derived from the erosion of the stratospheric ozone layer. Our results encourage design future research to further our understanding of UVB effects on the metabolic balance of plankton communities. Key Points UV sensitivity of planktonic NCP ©2014. American Geophysical Union. All Rights Reserved., This research was funded by the projects RODA (CTM-2004-06842-CO3-O2) and ATOS (POL2006-00550/CTM), Humboldt-2009 project (CTM2008-02497-E), MEDEICG (CTM2009-07013), and the Malaspina-2010 expedition project funded by the CONSOLIDER Ingenio-2010 program (CSD2008-00077), all funded by the National Plan of R + D of the Spanish Ministry of Science and Innovation. A.R.d.G. was supported by the EU Marie Curie EST project Metaoceans (MEST-CT-2005-019678)

Exchangeable organic carbon (OC) dynamics and CO2 fluxes in the Antarctic Peninsula during austral summer were highly variable, but the region appeared to be a net sink for OC and nearly in balance for CO2. Surface exchangeable dissolved organic carbon (EDOC) measurements had a 43±3 (standard error, hereafter SE) μmol CL-1 overall mean and represented around 66% of surface non-purgeable dissolved organic carbon (DOC) in Antarctic waters, while the mean concentration of the gaseous fraction of organic carbon (GOCH′-1) was 46±3 SE μmol C L -1. There was a tendency towards low fugacity of dissolved CO 2 (fCO2-w) in waters with high chlorophyll a (Chl a) content and high fCO2-w in areas with high krill densities. However, such relationships were not found for EDOC. The depth profiles of EDOC were also quite variable and occasionally followed Chl a profiles. The diel cycles of EDOC showed two distinct peaks, in the middle of the day and the middle of the short austral dark period, concurrent with solar radiation maxima and krill night migration patterns. However, no evident diel pattern for GOC H′-1 or CO2 was observed. The pool of exchangeable OC is an important and active compartment of the carbon budget surrounding the Antarctic Peninsula and adds to previous studies highlighting its importance in the redistribution of carbon in marine environments. © Author(s) 2014., This is a contribution of both Aportes Atmosféricos de Carbono Orgánico y Contaminanates al océano Polar (ATOS) and the Spanish component of the Synoptic Antarctic Shelf-Slope Interactions study (ESASSI), funded by the Spanish Ministry of Science under the scope of the International Polar Year (IPY). Maria Ll. Calleja was funded by the Spanish Research Council (CSIC, grant JAEDOC030) and cofounded by the Fondo Social Europeo (FSO)

Trabajo presentado en la Malaspina Annual Meeting 2010, celebrada en España, celebrada en abril de 2013

14 pages, 8 figures, 2 tables, Aim The emission of chlorofluorocarbon compounds eroded the ozone layer, raising incident ultraviolet B radiation to levels that affect biota. However, the role of UVB radiation (280–315 nm), which remains elevated to date, as a possible driver of the widespread global deterioration of marine ecosystems has not yet been fully quantified. In this paper we assess the magnitude of the impacts of elevated UVB radiation and evaluate the relative sensitivity to UVB across marine taxa and processes. Location The analyses presented are based on 1784 experimental assessments of the impacts of UVB performed with natural radiation and organisms from different geographical areas, as well as with artificial radiation and cultured organisms at many laboratories around the world. Methods First we compiled the published literature concerning experimental evaluation of the impacts of UVB on marine biota. Then a meta-analysis was conducted with the data set obtained to evaluate the responses of marine organisms and processes to enhanced and reduced UVB levels. Results Increased UVB radiation leads to a sharp increase in mortality rates across marine taxa, with protists, corals, crustaceans and fish eggs and larvae being most sensitive. A general relationship between relative changes in UVB doses and mortality rates was developed. This relationship can help assess the effects of changes in incident UVB radiation (past, present or future) on marine organisms. Main conclusions This meta-analysis demonstrates that mortality rates of marine biota increase rapidly in response to elevated UVB radiation. The enhanced mortality rates associated with currently elevated UVB levels may represent a major threat to marine biota, possibly underlying recent widespread declines in the abundance of marine organisms ranging from corals to fish and krill, This research is a contribution to the LINCGlobal programme (CSIC-PUC) and was partially funded by the Malaspina-2010 project of the CONSOLIDER programme (ref. CSD2008-00077) and the project MEDEICG (ref. CTM2009-07013) of the Spanish Ministry of Science and Innovation

Polar marine ecosystems have global ecological and economic importance because of their unique biodiversity and their major role in climate processes and commercial fisheries, among others. Portugal and Spain have been highly active in a wide range of disciplines in marine biology of the Antarctic and the Arctic. The main aim of this paper is to provide a synopsis of some of the results and initiatives undertaken by Portuguese and Spanish polar teams within the field of marine sciences, particularly on benthic and pelagic biodiversity (species diversity and abundance, including microbial, molecular, physiological and chemical mechanisms in polar organisms), conservation and ecology of top predators (particularly penguins, albatrosses and seals), and pollutants and evolution of marine organisms associated with major issues such as climate change, ocean acidification and UV radiation effects. Both countries have focused their polar research more in the Antarctic than in the Arctic. Portugal and Spain should encourage research groups to continue increasing their collaborations with other countries and develop multi-disciplinary research projects, as well as to maintain highly active memberships within major organizations, such as the Scientific Committee for Antarctic Research (SCAR), the International Arctic Science Council (IASC) and the Association of Polar Early Career Scientists (APECS), and in international research projects. Fundação para a Ciência e a Tecnologia PTDC/MAR/099366/2008, Pest-OE/MAR/UI0331/2011 Ministerio de Ciencia e Innovación POL2006-06399, CGL2007- 65453/ANT, CTM2010-17415/ANT, CLG2007-28872-E/ANT, REN2002-11565-E/ANT “CASES-2003/4” Xunta de Galicia CTM2009-11128ANT Fondo Europeo de Desarrollo Regional GL2007-64149/ANT, CTM2011-24007, REN2001-5004/ANT, CGL2004-01348, POL2006-05175, CGL2007-60369, CTM2009-08154-E, CTM2011- 24427

The gradient in the partial pressure of carbon dioxide (pCO2) across the air-sea boundary layer is the main driving force for the air-sea CO2 flux. Global data bases for surface seawater pCO2 are actually based on pCO2 measurements from several meters below the sea surface, assuming a homogeneous distribution between the diffusive boundary layer and the upper top meters of the ocean. Compiling vertical profiles of pCO2, temperature, and dissolved oxygen in the upper 5-8 m of the ocean from different biogeographical areas, we detected a mean difference between the boundary layer and 5 m pCO2 of 13 ± 1 μatm. Temperature gradients accounted for only 11% of this pCO2 gradient in the top meters of the ocean; thus, pointing to a heterogeneous biological activity underneath the air-sea boundary layer as the main factor controlling the top meters pCO2 variability. Observations of pCO2 just beneath the air-sea boundary layer should be further investigated in order to estimate possible biases in calculating global air-sea CO2 fluxes. Key Points High pCO2 vertical variability within the upper meters of the ocean surfaceOnly 11% of pCO2 variability appears to be explained by temperature changesBiological processes exert a control in the observed CO2 vertical heterogeneity ©2013. American Geophysical Union. All Rights Reserved.

Trabajo presentado en ASLO 2012 (Aquatic Sciences Meeting), celebrado del 8 al 13 de julio de 2012 en Lake Biwa, Shiga (Japón)

Trabajo presentado en 6th SETAC World Congress/SETAC Europe 22nd Annual Meeting, celebrado en Berlín (Alemania), del 20 al 24 de mayo de 2012

2012 Ocean Sciences Meeting, 20-24 February 2012, Salt Lake City, Utah, USA, Migrant biota transports carbon to the mesopelagic zone due to their feeding at the shallower layers and their defecation, respiration, excretion and mortality at depth. The so-called active flux has been considered a small number compared to gravitational sinking. Recent assessments in subtropical waters show an important effect due to predation by interzonal diel vertical migrants (DVMs). The consumption and subsequent transport of epipelagic zooplankton by DVMs (mainly micronekton) to the mesopelagic zone seemed similar to the mean gravitational export. However, the consequences of this active transport to the bathypelagic zone are almost unknown. Here, we show the effect of the Atlantic and Pacific equatorial upwelling systems on the vertical distribution of acoustic backscatter from the surface to bathypelagic depths. The enhancement of the acoustic signal below the upwelling zone was observed to reach 4000 m depth, coinciding with high abundances and activity of bacteria at those depths. The results suggest an active carbon transport from the epipelagic driven by zooplankton and micronekton, enhancing the efficiency of the biological pump and giving an insight about the fate of an increased productivity at the shallower layers of the ocean

Capítulo publicado en: Moreno Ostos, Enrique (ed.). Expedición de circunnavegación Malaspina 2010. Cambio global y exploración de la biodiversidad del océano. Libro blanco de métodos y técnicas de trabajo oceanográfico. Madrid: CSIC, 2012

Capítulo publicado en: Moreno Ostos, Enrique (ed.). Expedición de circunnavegación Malaspina 2010. Cambio global y exploración de la biodiversidad del océano. Libro blanco de métodos y técnicas de trabajo oceanográfico. Madrid: CSIC, 2012

Trabajo presentado en ASLO Aquatic Sciences Meeting (2011), celebrado en San Juan (Puerto Rico), del 13 al 17 de febrero de 2011, The Arctic region is experiencing the steepest warming rate on Earth, which is three times faster than the global mean. Here we examine changes of carbon fluxes from bacteria to larger predators by protists, and by viruses due to increased water temperature in the Arctic Ocean. Our aim is to resolve which is the effect of global warming affecting these microbial activity rates. During July 2009, we collected Arctic water to carry out a mesocosms experiment along 10 days and at 7 different temperatures from 1.5 to 10ºC. We have detected that all microbial abundances as well as bacterial production and fluxes of bacterial carbon due to grazers and viruses achieved maximum values around 4.5º- 6ºC experimental temperature, and maintained high values even at higher experimental temperatures. The biomass of phototrophs, has also shown maximum values at ca. 5ºC and a clear decrease at temperatures higher than 5ºC. The obtained results indicate that the increase of the water temperature is followed by a shift towards more heterotrophic community, which could have an impact on carbon storage in the Arctic region.

Trabajo presentado en ASLO Aquatic Sciences Meeting (2011), celebrado en San Juan (Puerto Rico), del 13 al 17 de febrero de 2011

In this article, we review evidence of how climate change has already resulted in clearly discernable changes in marine Arctic ecosystems. After defining the term 'footprint' and evaluating the availability of reliable baseline information we review the published literature to synthesize the footprints of climate change impacts in marine Arctic ecosystems reported as of mid-2009. We found a total of 51 reports of documented changes in Arctic marine biota in response to climate change. Among the responses evaluated were range shifts and changes in abundance, growth/condition, behaviour/phenology and community/regime shifts. Most reports concerned marine mammals, particularly polar bears, and fish. The number of well-documented changes in planktonic and benthic systems was surprisingly low. Evident losses of endemic species in the Arctic Ocean, and in ice algae production and associated community remained difficult to evaluate due to the lack of quantitative reports of its abundance and distribution. Very few footprints of climate change were reported in the literature from regions such as the wide Siberian shelf and the central Arctic Ocean due to the limited research effort made in these ecosystems. Despite the alarming nature of warming and its strong potential effects in the Arctic Ocean the research effort evaluating the impacts of climate change in this region is rather limited. © 2010 Blackwell Publishing Ltd., This research is a contribution to the Arctic Tipping Points project (http://www.eu-atp.org) funded by FP7 of the European Union (contract 226248) and ARCTOS, a north-Norwegian network that emphasises interdisciplinary approaches to addressing large-scale questions in marine Arctic oceanography (http://www.arctosresearch.net).

Trabajo presentado en ASLO Aquatic Sciences Meeting (2011), celebrado en San Juan (Puerto Rico), del 13 al 17 de febrero de 2011

Trabajo presentado en Arctic Frontiers 2011, Arctic Tipping Points, celebrado en Tromso (Noruega), del 23 al 28 de enero de 2011. El libro de abstracts se publicó como: 2011 Abstracts. Arctic Frontiers. The Arctic in the Earth System Perspective: the role of tiping points. Tromso: [University of Tromso, 2011], The Arctic region is experiencing the steepest warming rate on Earth, which is three times faster than the global mean. In order to solve which is the effect of global warming affecting Arctic microbial communities, we examine the effect of increasing temperatures on prokaryotes production, and mortality (by bacterivores and viruses) as well as changes in the community composition of protist from two contrasting Arctic marine systems. During July 2009, we collected Arctic, and Atlantic influenced waters to carry out two mesocosms experiment along 10 days each and at 7 increasing temperatures from 1.5 to 10ºC. Different responses at increasing temperatures were found for the microbial communities from different systems. Thus, for the Arctic microbial community, adapted to live at ¿ 1.5º C, we have detected that all microbial abundances as well as bacterial production and fluxes of bacterial carbon due to grazers and viruses achieved maximum values around 4.5º- 6ºC experimental temperature, and maintained high values even at higher experimental temperatures. In addition, ciliates community composition showed a shift, increasing heterotrophic and bacterivores organisms at increasing temperatures. The biomass of phototrophs, has also shown maximum values at ca. 5ºC and a clear decrease at temperatures higher than 5ºC. In contrast, in the Atlantic-influenced community living at temperatures around 4ºC no clear response to increasing temperature was found. Our results indicate that communities used to to live at very low temperatures would suffer a higher impact than communities living at higher temperatures.

Trabajo presentado en la 'The Arctic as a Messenger for Global Processes - Climate Change and Pollution' Conference, celebrada en Copenhague, Dinamarca, del 4 al 6 de mayo de 2011

Póster presentado en el VIII Simposio de Estudios Polares (8th Symposium on Polar Studies), celebrado del 7 al 9 de septiembre de 2011 en Palma de Mallorca (España)

22 páginas, Financial support of the BBVA Foundation

Trabajo incluido en el libro: Duarte, Carlos M.; Wassmann, Paul (eds.). Arctic Tipping Points. Bilbao: Fundación BBVA, 2011

Trabajo presentado en la Arctic Frontiers Meeting, celebrada en Noruega, del 24 al 28 de enero de 2011, The Arctic region is experiencing the steepest warming rate on Earth, which is three times faster than the global mean. In order to solve which is the effect of global warming affecting Arctic microbial communities, we examine the effect of increasing temperatures on prokaryotes production, and mortality (by bacterivores and viruses) as well as changes in the community composition of protist from two contrasting Arctic marine systems. During July 2009, we collected Arctic, and Atlantic influenced waters to carry out two mesocosms experiment along 10 days each and at 7 increasing temperatures from 1.5 to 10ºC. Different responses at increasing temperatures were found for the microbial communities from different systems. Thus, for the Arctic microbial community, adapted to live at ¿ 1.5º C, we have detected that all microbial abundances as well as bacterial production and fluxes of bacterial carbon due to grazers and viruses achieved maximum values around 4.5º- 6ºC experimental temperature, and maintained high values even at higher experimental temperatures. In addition, ciliates community composition showed a shift, increasing heterotrophic and bacterivores organisms at increasing temperatures. The biomass of phototrophs, has also shown maximum values at ca. 5ºC and a clear decrease at temperatures higher than 5ºC. In contrast, in the Atlantic-influenced community living at temperatures around 4ºC no clear response to increasing temperature was found. Our results indicate that communities used to to live at very low temperatures would suffer a higher impact than communities living at higher temperatures.

Trabajo incluido en el libro: Duarte, Carlos M.; Wassmann, Paul (eds.). Arctic Tipping Points. Bilbao: Fundación BBVA, 2011

22 páginas Financial support of the BBVA Foundation

Trabajo presentado en el 2010 Ocean Sciences Meeting, celebrado del 22 al 26 de febrero de 2010 en Portland, Oregon (Estados Unidos)

Trabajo presentado en la SETAC Europe 20th Annual Meeting, celebrada en Sevilla, España, del 23 al 27 de mayo de 2010

22 páginas, La constatación de que nuestro planeta se encuentra inmerso en un proceso de calentamiento global, al que subyace la emisión de gases de efecto invernadero como consecuencia de la actividad humana, ha centrado la atención en el impacto que este cambio puede provocar sobre la sociedad y el medio ambiente. Los ecosistemas polares se vislumbran entre los más vulnerables del planeta, aunque aún no se ha evaluado suficientemente el alcance de los efectos derivados de esta alteración. El Año Polar Internacional que ahora estamos celebrando –cuyas actividades se desarrollan desde marzo de 2007 hasta marzo de 2009– ofrece una ocasión particularmente apropiada para cubrir esta laguna en nuestro conocimiento. Este libro recoge la segunda serie de debates organizados conjuntamente por el Consejo Superior de Investigaciones Científicas (CSIC) y la Fundación BBVA. En sus páginas, un elenco de científicos internacionales de gran prestigio revisa el estado actual del conocimiento científico existente para, a través de su síntesis, evaluar el posible impacto del calentamiento climático sobre los ecosistemas polares, Financial support of the BBVA Foundation.

Air-sea CO2 exchange depends on the air-sea CO2 gradient and the gas transfer velocity (k), computed as a function of wind speed. Large discrepancies among relationships predicting k from wind suggest that other processes also contribute significantly to modulate CO2 exchange. Here we report, on the basis of the relationship between the measured gas transfer velocity and the organic carbon concentration at the ocean surface, a significant role of surface organic matter in suppressing air-sea gas exchange, at low and intermediate winds, in the open ocean, confirming previous observations. The potential role of total surface organic matter concentration (TOC) on gas transfer velocity (k) was evaluated by direct measurements of air-sea CO2 fluxes at different wind speeds and locations in the open ocean. According to the results obtained, high surface organic matter contents may lead to lower air-sea CO2 fluxes, for a given air-sea CO 2 partial pressure gradient and wind speed below 5ms-1, compared to that observed at low organic matter contents. We found the bias in calculated gas fluxes resulting from neglecting TOC to co-vary geographically and seasonally with marine productivity. These results support previous evidences that consideration of the role of organic matter in modulating air-sea CO2 exchange may improve flux estimates and help avoid possible bias associated to variability in surface organic concentration across the ocean. © Author(s) 2009.

Trabajo presentado en el 2008 Ocean Sciences Meeting, From the Watershed to the Global Ocean, celebrado en Orlando, Florida (Estados Unidos), del 2 al 7 de Marzo de 2008.