Interaction between elevated co2 and organic matter on bacterial metabolismo

Aquatic Sciences Meeting (Aquatic Sciences: Global And Regional Perspectives - North Meets South), 22-27 February 2015, Granada, Spain.Microcosm experiments to assess bacterioplankton response to autochthonous inputs of organic matter modified by future acidified ocean conditions were performed. Surface seawater enriched with inorganic nutrients and incubated in UVR-transparent cubitainers was bubbled for 8 days with regular air (380 ppmv CO2) or with a high CO2-air mixture (1000 ppmv CO2) to be used as inocula. In the second phase of the experiment, natural bacterioplankton communities enriched with the acidified or non-acidified organic matter inocula were incubated under dark conditions during 8 days in the presence or absence of CO2 as previously. Bacterial abundance, production and viability were measured as physiological indicators of bacterial metabolism. The results showed that acidified organic matter produced higher abundances for similar production rates early during the incubation, while non-acidified organic matter produced higher bacterial production and viability latter at the end of the experiment, indicating a more recalcitrant character of the organic matter under these conditions. We demonstrate that CO2 effects on bacterioplankton are mainly due to indirect effects on organic matter characteristics rather than to direct effects of acidification on bacteria metabolism.N

Description of an experimental set up for the culture of benthic foraminifera in controlled pH conditions

10 páginas, 4 figuras, 1 tabla[EN] Acidification of the oceans is one of the consequences of ongoing increasing atmospheric CO2 concentrations. The effects on organisms that build their shells of calcium carbonate are not sufficiently studied and might be detrimental. Simulating ocean acidification scenarios in the laboratory is a reasonable way to study their response to decreased pH and carbonate ion concentrations. In this study we describe in detail an experimental system to carry out ocean acidification experiments with non-symbiotic benthic foraminifera. We test the performance of the designed experimental set up by running a long-term experiment (90 days) using a potentially suitable benthic foraminiferal species for culturing (Miliolinella spp.). Although foraminifera did not survive the experimental period likely due to ciliates infestation, seawater pH measurement results indicate that the design is suitable for carrying out ocean acidification experiments[ES] La acidificación oceánica es una de las consecuencias del aumento progresivo de la concentración de CO2 en la atmósfera. Los efectos en los organismos que construyen sus conchas con carbonato cálcico no están suficientemente estudiados, pero podrían ser perjudiciales. La simulación en laboratorio de diferentes escenarios de acidificación oceánica es una forma de estudiar la respuesta de esos organismos al descenso de pH y de la concentración del ion carbonato. En este estudio se describe minuciosamente un sistema experimental diseñado para realizar experimentos de acidificación oceánica con foraminíferos bentónicos sin simbiontes. La viabilidad del diseño experimental se ha probado con un experimento de larga duración (90 días) utilizando una especie de foraminífero bentónico potencialmente apta para ser cultivada (Miliolinella spp.). Aunque los foraminíferos no sobrevivieron durante todo el experimento debido a contaminación por ciliados, los resultados de las medidas del pH marino ponen de manifiesto que el diseño es adecuado para llevar a cabo experimentos de acidificación oceánicaThis research leading to these results was supported by the Spanish Ministry of Sciences and Innovation and co-founded by the Fondo Europeo de Desarrollo Regional 2007-2012 (FEDER) through the CATARINA Project (CTM2010-17141/MAR) and GRACCIEPeer reviewe

Turnover time of fluorescent dissolved organic matter in the dark global ocean

Research articleMarine dissolved organic matter (DOM) is one of the largest reservoirs of reduced carbon on Earth. In the dark ocean (4200 m), most of this carbon is refractory DOM. This refractory DOM, largely produced during microbial mineralization of organic matter, includes humic-like substances generated in situ and detectable by fluorescence spectroscopy. Here we show two ubiquitous humic-like fluorophores with turnover times of 435±41 and 610±55 years, which persist significantly longer than the B350 years that the dark global ocean takes to renew. In parallel, decay of a tyrosine-like fluorophore with a turnover time of 379±103 years is also detected. We propose the use of DOM fluorescence to study the cycling of resistant DOM that is preserved at centennial timescales and could represent a mechanism of carbon sequestration (humic-like fraction) and the decaying DOM injected into the dark global ocean, where it decreases at centennial timescales (tyrosine-like fraction).Versión del editor10,015

Short-term variability in the activity and composition of the diazotroph community in a coastal upwelling system

Today we know that diazotrophs are common and active in nitrogen (N) replete regions, however the factors controlling their distribution remain elusive. Previous studies in upwelling regions revealed that the composition of diazotrophs responded to changes in hydrodynamic forcing over seasonal scales. Here we used high-frequency observations collected during a 3-week cruise in the upwelling region off NW Iberia to describe changes in the activity and composition of diazotrophs over shorter temporal scales. The cruise started after a strong upwelling event followed by a few days of relaxation-downwelling, and soon after another upwelling pulse. Higher N2 fixation rates (2.2 ± 0.7 µmol m-3 d-1) were measured during relaxation-downwelling, when surface nitrate concentration was low. During the fertilization associated with the upwelling, N2 fixation dramatically decreased to 0.10 ± 0.09 µmol m-3 d-1. The comparison with nitrate consumption and diffusion confirmed the minor role of N2 fixation (<1%) as a source of new N for primary production. The unicellular cyanobacterium UCYN-A2 was the dominant diazotroph during the cruise. UCYN-A2 abundance was four times higher during relaxation-downwelling (4x104 copies L-1) compared to upwelling conditions (0.2x104 copies L-1), when the unusual Epsilonproteobacteria increased their relative abundance. These results indicate that diazotrophs can respond rapidly to changes in the environment, and point out to the availability of N as a key factor controlling the activity, composition and distribution of diazotrophs in eutrophic regions

Water mass age and ageing driving chromophoric dissolved organic matter in the dark global ocean

Research articleThe omnipresence of chromophoric dissolved organic matter (CDOM) in the open ocean enables its use as a tracer for biochemical processes throughout the global overturning circulation. We made an inventory of CDOM optical properties, ideal water age (τ), and apparent oxygen utilization (AOU) along the Atlantic, Indian, and Pacific Ocean waters sampled during the Malaspina 2010 expedition. A water mass analysis was applied to obtain intrinsic, hereinafter archetypal, values of τ, AOU, oxygen utilization rate (OUR), and CDOM absorption coefficients, spectral slopes and quantum yield for each one of the 22 water types intercepted during this circumnavigation. Archetypal values of AOU and OUR have been used to trace the differential influence of water mass aging and aging rates, respectively, on CDOM variables. Whereas the absorption coefficient at 325nm (a325) and the fluorescence quantum yield at 340nm (Φ340) increased, the spectral slope over the wavelength range 275–295nm (S275–295) and the ratio of spectral slopes over the ranges 275–295nm and 350–400nm (SR) decreased significantly with water mass aging (AOU). Combination of the slope of the linear regression between archetypal AOU and a325 with the estimated global OUR allowed us to obtain a CDOM turnover time of 634 ± 120 years, which exceeds the flushing time of the dark ocean (>200 m) by 46%. This positive relationship supports the assumption of in situ production and accumulation of CDOM as a by-product of microbial metabolism as water masses turn older. Furthermore, our data evidence that global-scale CDOM quantity (a325) is more dependent on aging (AOU), whereas CDOM quality (S275–295, SR, Φ340) is more dependent on aging rate (OUR).Versión del editor4,785

Papers from the 4. International conference of the Spanish Society for Medieval English Language and Literature

Centro de Informacion y Documentacion Cientifica (CINDOC). C/Joaquin Costa, 22. 28002 Madrid. SPAIN / CINDOC - Centro de Informaciòn y Documentaciòn CientìficaSIGLEESSpai

Effects of elevated CO₂ and phytoplankton-derived organic matter on the metabolism of bacterial communities from coastal waters

Microcosm experiments to assess the bacterioplankton's response to phytoplankton-derived organic matter obtained under current and future ocean CO2 levels were performed. Surface seawater enriched with inorganic nutrients was bubbled for 8 days with air (current CO2 scenario) or with a 1000&thinsp;ppm CO2 air mixture (future CO2 scenario) under solar radiation. The organic matter produced under the current and future CO2 scenarios was subsequently used as an inoculum. Triplicate 12&thinsp;L flasks filled with 1.2&thinsp;µm of filtered natural seawater enriched with the organic matter inocula were incubated in the dark for 8 days under CO2 conditions simulating current and future CO2 scenarios, to study the bacterial response. The acidification of the media increased bacterial respiration at the beginning of the experiment, while the addition of the organic matter produced under future levels of CO2 was related to changes in bacterial production and abundance. This resulted in a 67&thinsp;% increase in the integrated bacterial respiration under future CO2 conditions compared to present CO2 conditions and 41&thinsp;% higher integrated bacterial abundance with the addition of the acidified organic matter compared to samples with the addition of non acidified organic matter. This study demonstrates that the increase in atmospheric CO2 levels can impact bacterioplankton metabolism directly, by changes in the respiration rate, and indirectly, by changes on the organic matter, which affected bacterial production and abundance.</p

Effect of solar UVR on the production of particulate and dissolved organic carbon from phytoplankton assemblages in the Indian Ocean

15 pages, 5 figures, 4 tablesThis study shows the effects of solar UVR on the photosynthetic parameters and the production of both particulate and dissolved organic carbon (POC and DOC, respectively) of phytoplankton assemblages from oligotrophic areas of the southeastern Indian Ocean. Samples from the 20% PAR depth were incubated on deck under different intensities of 2 different light regimes: full solar radiation (PAR+UVR) and excluding UVR (PAR). Phytoplankton production was measured by the 14C method, obtaining size-fractionated POC (0.2, 2 and 20 µm), total POC and DOC. POC values were fit to a photosynthesis-irradiance (P-E) model that includes photoinhibition. Phytoplankton populations under PAR+UVR had a 10% lower maximum photosynthetic rate (PsB) and an 86% higher sensitivity to inhibition (β) than populations incubated under only PAR exposures. For some stations, cells larger than 2 µm showed higher PsB and photosynthetic efficiency (measured as the P-E slope, α) than smaller cells, but no significant differences were found for β. In contrast, DOC production was significantly higher under PAR+UVR than under PAR exposures and did not follow the P-E model used for fitting POC. The analysis of the P-E values for DOC production showed that values remained constant under PAR intensities but increased with increasing irradiance in the presence of UVR. In some cases, inhibition of DOC production at high irradiances was also observed. These results demonstrate the relevance of UVR irradiance as an environmental driver for phytoplanktonic DOC production in oligotrophic waters and reinforce the important role of UVR on the physiology and ecology of tropical planktonThis study was possible thanks to the project Malaspina 2010 from the Spanish Ministry of Innovation and Science (MICINN, Consolider 2008-00077), the crew of the RV ‘Hespérides’ and staff of the Marine Technological Unit (UTM)Peer Reviewe

Differential response of planktonic primary, bacterial, and dimethylsulfide production rates to static vs. dynamic light exposure in upper mixed-layer summer sea waters

16 pages, 8 figures, 1 tableMicrobial plankton experience short-term fluctuations in total solar irradiance and in its spectral composition as they are vertically moved by turbulence in the oceanic upper mixed layer (UML). The fact that the light exposure is not static but dynamic may have important consequences for biogeochemical processes and ocean-atmosphere fluxes. However, most biogeochemical processes other than primary production, like bacterial production or dimethylsulfide (DMS) production, are seldom measured in sunlight and even less often in dynamic light fields. We conducted four experiments in oligotrophic summer stratified Mediterranean waters, where a sample from the UML was incubated in ultraviolet (UV)-transparent bottles at three fixed depths within the UML and on a vertically moving basket across the same depth range. We assessed the response of the phyto- and bacterioplankton community with physiological indicators based on flow cytometry singe-cell measurements, fast repetition rate fluorometry (FRRf), phytoplankton pigment concentrations and particulate light absorption. Dynamic light exposure caused a subtle disruption of the photoinhibition and photoacclimation processes associated with ultraviolet radiation (UVR), which slightly alleviated bacterial photoinhibition but did not favor primary production. Gross DMS production (GPDMS) decreased sharply with depth in parallel to shortwave UVR, and displayed a dose-dependent response that mixing did not significantly disrupt. To our knowledge, we provide the first measurements of GPDMS under in situ UV-inclusive optical conditions. © 2013 Author(s)M. G. acknowledges the receipt of a CSIC JAE scholarship. This work was supported by the (former) Spanish Ministry of Science and Innovation through the project SUMMER (CTM2008-03309/MAR). This is a contribution of the Research Groups on Marine Biogeochemistry and Global Change and on Aquatic Microbial Food Webs, supported by the Generalitat de CatalunyaPeer Reviewe

Carbon metabolism responses in acclimated and perturbed emiliania huxleyi cultures under ocean acidification conditions

12th International Phycological Congress, 22-26 March 2021Carbon metabolism related variables in Emiliania huxleyi show variable responses to ocean cidification (OA). However, most of the studies converge on the statement that OA has negative effects on alcification. In this study we hypothesize that carbon metabolic responses to OA differ between CO2 acclimated and perturbed phytoplankton cultures. Hence, responses of Emiliania huxleyi cultures acclimated to future CO2 concentrations (1000 ppmv, High Carbon: HC) and present CO2 concentrations (406 ppmv, Low Carbon: LC, Control) were assessed under acclimated and perturbed conditions, the last one promoted by stopping the CO2 supply in the culture media for 4 hours. Gene expression of three genes related to CCMs (Carbonic anhydrase (CA): αca1, αca2) and carbon fixation (RuBisCO: rbcL) were quantified as well as rates of photosynthetic carbon incorporation, DOC release and calcification. The results revealed two different patterns in both, molecular and physiological responses, depending on culture conditions and CO2 treatment: acclimated conditions performed a down-regulation of the carbon metabolism in HC cells compared to LC cells while under perturbed conditions, HC cells showed an up-regulation of most of the photosynthetic carbon metabolic pathways studied. In addition, the calcification rates under HC concentrations revealed a more conservative response than the other tested variables and always showed lower values than under LC conditions. These results highlight the relevance of considering previous growth conditions to appropriately interpret the response of calcifying phytoplankton to future OA scenariosThis work has been funded by the Spanish Ministry of Economy, Industry and Competitiveness and by the Xunta de GaliciaN