Prokaryotic respiration and production in the meso- and bathypelagic realm of the eastern and western North Atlantic basin

We measured prokaryotic production and respiration in the major water masses of the North Atlantic down to a depth of,4,000 m by following the progression of the two branches of North Atlantic Deep Water (NADW) in the oceanic conveyor belt. Prokaryotic abundance decreased exponentially with depth from 3 to 0.4 3 105 cells mL21 in the eastern basin and from 3.6 to 0.3 3 105 cells mL21 in the western basin. Prokaryotic production measured via 3H-leucine incorporation showed a similar pattern to that of prokaryotic abundance and decreased with depth from 9.2 to 1.1 mmol C m23 d21 in the eastern and from 20.6 to 1.2 mmol C m23 d21 in the western basin. Prokaryotic respiration, measured via oxygen consumption, ranged from about 300 to 60 mmol C m23 d21 from,100 m depth to the NADW. Prokaryotic growth efficiencies of,2 % in the deep waters (depth range 1,200–4,000 m) indicate that the prokaryotic carbon demand exceeds dissolved organic matter input and surface primary production by 2 orders of magnitude. Cell-specific prokaryotic production was rather constant throughout the water column, ranging from 15 to 32 3 1023 fmol C cell21 d21 in the eastern and from 35 to 58

Bottom-up control of sardine and anchovy population cycles in the canary current: insights from an end-to-end model simulation

Sardine and anchovy can exhibit dramatic decadal-scale shifts in abundance in response to climate variability. Sharpe declines of these populations entail particularly serious commercial and ecological consequences in eastern boundary current ecosystems, where they sustain major world fisheries and provide the forage for a broad variety of predators. Understanding the mechanisms and environmental forcing that drive the observed fish variability remains a challenging problem. The modelling study presented here provides an approach that bridges a comprehensive database with an end-to-end modelling framework enabling the investigation of the sources of variability of sardine and anchovy in the Canary Current System. Different biological traits and behaviour prescribed for sardine and anchovy gave rise to different distribution and displacements of the populations, but to a rather synchronous variability in terms of abundance and biomass, in qualitative agreement with historical landing records. Analysis of years with anomalously high increase and decline of the adult population points to food availability (instead of temperature or other environmental drivers) as the main environmental factor determining recruitment for both sardine (via spawning and survival of feeding age-0 individuals) and anchovy (via survival of feeding age-0). Consistent with this, the two species thrive under enhanced upwelling-favourable winds, but only up to some threshold of the wind velocity beyond which larval drift mortality exceeds the positive effect of the extra food supply. Based on the analysis of the simulation, we found that anchovy larvae are particularly vulnerable to enhanced wind-driven advection, and as such do better with more moderate upwelling than sardines.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Photochemical vs. Bacterial Control of H2O2 Concentration Across a pCO2 Gradient Mesocosm Experiment in the Subtropical North Atlantic

In the surface ocean, microorganisms are both a source of extracellular H2O2 and, via the production of H2O2 destroying enzymes, also one of the main H2O2 sinks. Within microbial communities, H2O2 sources and sinks may be unevenly distributed and thus microbial community structure could influence ambient extracellular H2O2 concentrations. Yet the biogeochemical cycling of H2O2 and other reactive oxygen species (ROS) is rarely investigated at the community level. Here, we present a time series of H2O2 concentrations during a 28-day mesocosm experiment where a pCO2 gradient (400–1,450 μatm) was applied to subtropical North Atlantic waters. Pronounced changes in H2O2 concentration were observed over the duration of the experiment. Initially H2O2 concentrations in all mesocosms were strongly correlated with surface H2O2 concentrations in ambient seawaters outside the mesocosms which ranged from 20 to 92 nM over the experiment duration (Spearman Rank Coefficients 0.79–0.93, p-values 300 nM in some mesocosms (2–6 fold higher than ambient seawaters). The correlation with ambient H2O2 was then no longer significant (p > 0.05) in all treatments. Furthermore, changes in H2O2 could not be correlated with inter-day changes in integrated irradiance. Yet H2O2 concentrations in most mesocosms were inversely correlated with bacterial abundance (negative Spearman Rank Coefficients ranging 0.59–0.94, p-values < 0.001–0.03). Our results therefore suggest that ambient H2O2 concentration can be influenced by microbial community structure with shifts toward high bacterial abundance correlated with low extracellular H2O2 concentrations. We also infer that the nature of mesocosm experiment design, i.e., the enclosure of water within open containers at the ocean surface, can strongly influence extracellular H2O2 concentrations. This has potential chemical and biological implications during incubation experiments due to the role of H2O2 as both a stressor to microbial functioning and a reactive component involved in the cycling of numerous chemical species including, for example, trace metals and haloalkanes

Longitudinal variability of size-fractionated N-2 fixation and DON release rates along 24.5 degrees N in the subtropical North Atlantic

Dinitrogen (N-2) fixation and dissolved organic nitrogen (DON) release rates were measured on fractionated samples (\u3e10 mu m and m) along 24.5 degrees N in the subtropical North Atlantic. Net N-2 fixation rates (N-2 assimilation into biomass) ranged from 0.01 to 0.4 nmol N L-1 h(-1), and DON release rates ranged from 0.001 to 0.09 nmol N L-1 h(-1). DON release represented approximate to 14% and approximate to 23% of \u3e10 mu m and (assimilation into biomass plus DON release), respectively. This implies that by overlooking DON release, N-2 fixation rates are underestimated. Net N-2 fixation rates were higher in the east and decreased significantly toward the west (r(s)=-0.487, p=0.002, and r(s)=-0.496, p=0.001, for the \u3e10 mu m and fractions, respectively). The sum of both fractions correlated with aerosol optical depth at 550 nm (AOD 550 nm) (r(s)=0.382, p=0.017) and phosphate (PO43-) concentrations (r(s)=0.453, p=0.018), suggesting an enhancement of diazotrophy as a response to aerosol inputs and phosphorus availability. In contrast, DON release was constant among size fractions and did not correlate with any of these variables. We also compared N-2 fixation rates obtained using the N-15(2) dissolved and bubble methods. The first gave average rates 50% (49% 39) higher than the latter, which supports the finding that previously published N-2 fixation rates are likely underestimated. We suggest that by combining N-2 fixation and DON release measurements using dissolved N-15(2), global N-2 fixation rates could increase enough to balance oceanic fixed nitrogen budget disequilibria

Examining the Relation Between Practicing Meditation and Having Peak Experiences and Lucid Dreams. A Cross-Sectional Study

The aim of this study was to compare meditators and non-meditators in terms of their tendency to have peak experiences and their dream lucidity, while examining the associations between these outcomes and some related variables such as non-dual awareness, mindfulness facets and absorption. In this cross-sectional study, 237 participants from general Spanish population completed an online survey that included ad hoc questions related to the study aim, along with the Five Facet Mindfulness Questionnaire (FFMQ), the Non-dual Embodiment Thematic Inventory (NETI), the Tellegen Absorption Scale (TAS) and the Lucidity and Consciousness in Dreams Scale (LUCID). Of the total, 110 participants were identified as meditators and 127 as non-meditators. More than half of the sample (58.2%) reported having experienced at least one peak experience in their life; these showed no differences in the number, intensity, or self-inducing ability of these experiences between both groups but were significantly more common among meditators (71.8% vs. 46.8%; p < 0.001), who also presented higher scores in most of the questionnaires, except for some LUCID subscales. Regression models demonstrated that being a meditator was a significant predictor of having had a peak experience, but not of LUCID scores. These results, which need to be interpreted considering the study limitations, support the potential of meditation to facilitate having peak experiences, while its impact on lucid dreams remains unclear

Biogeochemistry of dissolved and suspended organic matter in the Cape Vert Frontal Zone (NW Africa)

Oral communicationThe Cape Verde Frontal Zone (CVFZ) in the southern boundary of the Canary Current Upwelling Ecosystem, is a highly dynamic area, featuring large vertical and horizontal export fluxes of organic matter (OM) due to the interaction of the Cape Verde Front (CVF) with the Mauritanian upwelling. To study the interplay between transport and biogeochemical processes driving the distribution of OM in the CVFZ, full-depth profiles of dissolved (DOM) and suspended particulate (POM) OM were obtained during the FLUXES I cruise in August 2017. Distributions of surface DOM and POM and their stoichiometry were influenced by the mesoscale variability at the frontal region, showing significant differences north and south of the CVF and between stations close and distant to the Mauritanian coast. The C&colon;N molar ratio of DOM and POM showed average vertical gradients, increasing from 12.1 and 8.0 in surface to 15.6 and 17.0 respectively in deeps waters, deviating from the traditional Redfield ratio. In the meso- and bathypelagic zones, meridional and cross-shore gradients were detected within samples belonging to the same water mass, indicating that their properties were re-shaped by biogeochemical processes within the CVFZ. Correlations between apparent oxygen utilization and OM indicate that DOM&plus;POM contributed only to 8.1&percnt; of the carbon and 17.8&percnt; of the nitrogen mineralisation in the water column, suggesting that the local carbon demand is mainly supported by sinking POM and N containing compounds are mineralised to a larger extend than C containing compoundsASL

Response of subtropical phytoplankton communities to ocean acidification under oligotrophic conditions and during nutrient fertilization

The subtropical oceans are home to the largest phytoplankton biome on the planet. Yet, little is known about potential impacts of ocean acidification (OA) on phytoplankton community composition in the vast oligotrophic ecosystems of the subtropical gyres. To address this question, we conducted an experiment with 9 in situ mesocosms (~35 m3) off the coast of Gran Canaria in the eastern subtropical North Atlantic over a period of 9 weeks. By establishing a gradient of pCO2 ranging from ~350 to 1025 µatm, we simulated carbonate chemistry conditions as projected until the end of the 21st century. Furthermore, we injected nutrient-rich deep water into the mesocosms halfway through the experiment to simulate a natural upwelling event, which regularly leads to patchy nutrient fertilization in the study region. The temporal developments of major taxonomic groups of phytoplankton were analyzed by flow cytometry, pigment composition and microscopy. We observed distinct shifts in phytoplankton community structure in response to high CO2, with markedly different patterns depending on nutrient status of the system. Phytoplankton biomass during the oligotrophic phase was dominated by picocyanobacteria (Synechococcus), which constituted 60-80% of biomass and displayed significantly higher cell abundances at elevated pCO2. The addition of deep water triggered a substantial bloom of large, chain-forming diatoms (mainly Guinardia striata and Leptocylindrus danicus) that dominated the phytoplankton community during the bloom phase (70-80% of biomass) and until the end of the experiment. A CO2 effect on bulk diatom biomass became apparent only in the highest CO2 treatments (>800 µatm), displaying elevated concentrations especially in the stationary phase after nutrient depletion. Notably, these responses were tightly linked to distinct interspecific shifts within the diatom assemblage, particularly favoring the largest species Guinardia striata. Other taxonomic groups contributed less to total phytoplankton biomass, but also displayed distinct responses to OA treatments. For instance, higher CO2 favored the occurrence of prymnesiophyceae (Phaeocystis globosa) and dictyochophyceae, whereas dinoflagellates were negatively affected by increasing CO2. Altogether, our findings revealed considerable shifts in species composition in response to elevated CO2 and indicated that phytoplankton communities in the subtropical oligotrophic oceans might be profoundly altered by ocean acidification

Experiment design and bacterial abundance control extracellular H2O2 concentrations during four series of mesocosm experiments

The extracellular concentration of H2O2 in surface aquatic environments is controlled by a balance between photochemical production and the microbial synthesis of catalase and peroxidase enzymes to remove H2O2 from solution. In any kind of incubation experiment, the formation rates and equilibrium concentrations of reactive oxygen species (ROSs) such as H2O2 may be sensitive to both the experiment design, particularly to the regulation of incident light, and the abundance of different microbial groups, as both cellular H2O2 production and catalase–peroxidase enzyme production rates differ between species. Whilst there are extensive measurements of photochemical H2O2 formation rates and the distribution of H2O2 in the marine environment, it is poorly constrained how different microbial groups affect extracellular H2O2 concentrations, how comparable extracellular H2O2 concentrations within large-scale incubation experiments are to those observed in the surface-mixed layer, and to what extent a mismatch with environmentally relevant concentrations of ROS in incubations could influence biological processes differently to what would be observed in nature. Here we show that both experiment design and bacterial abundance consistently exert control on extracellular H2O2 concentrations across a range of incubation experiments in diverse marine environments. During four large-scale (>1000 L) mesocosm experiments (in Gran Canaria, the Mediterranean, Patagonia and Svalbard) most experimental factors appeared to exert only minor, or no, direct effect on H2O2 concentrations. For example, in three of four experiments where pH was manipulated to 0.4–0.5 below ambient pH, no significant change was evident in extracellular H2O2 concentrations relative to controls. An influence was sometimes inferred from zooplankton density, but not consistently between different incubation experiments, and no change in H2O2 was evident in controlled experiments using different densities of the copepod Calanus finmarchicus grazing on the diatom Skeletonema costatum (<1 % change in [H2O2] comparing copepod densities from 1 to 10 L−1). Instead, the changes in H2O2 concentration contrasting high- and low-zooplankton incubations appeared to arise from the resulting changes in bacterial activity. The correlation between bacterial abundance and extracellular H2O2 was stronger in some incubations than others (R2 range 0.09 to 0.55), yet high bacterial densities were consistently associated with low H2O2. Nonetheless, the main control on H2O2 concentrations during incubation experiments relative to those in ambient, unenclosed waters was the regulation of incident light. In an open (lidless) mesocosm experiment in Gran Canaria, H2O2 was persistently elevated (2–6-fold) above ambient concentrations; whereas using closed high-density polyethylene mesocosms in Crete, Svalbard and Patagonia H2O2 within incubations was always reduced (median 10 %–90 %) relative to ambient waters

IMBeR into the future Science Plan and Implementation Strategy 2016-2025

The Integrated Marine Biosphere Research (IMBeR) project, formerly the Integrated Marine Biogeochemistry and Ecosystem Research (IMBER1) project, is a global environmental change research initiative. Since its start in 2005, IMBeR has advanced understanding about potential marine environmental effects of global change, and the impacts and linkages to human systems at multiple scales. It is apparent that complex environmental issues and associated societal/sustainability choices operate at and across the interfaces of natural and social sciences and the humanities, and require both basic, curiosity-driven research and problem-driven, policy-relevant research. Collaborative, disciplinary, interdisciplinary, transdisciplinary and integrated research that addresses key ocean science issues generated by and/or impacting society is required to provide evidence-based knowledge and guidance, along with options for policy-makers, managers and marine-related communities, to help achieve sustainability of the marine realm under global change. This recognition underlies a new vision, “Ocean sustainability under global change for the benefit of society”, to guide IMBeR research for the next decade (2016-2025). This vision recognises that the evolution of marine ecosystems (including biogeochemical cycles and human systems) is linked to natural and anthropogenic drivers and stressors, as articulated in the new IMBeR research goal to, “Understand, quantify and compare historic and present structure and functioning of linked ocean and human systems to predict and project changes including developing scenarios and options for securing or transitioning towards ocean sustainability”. To implement its new vision and goal in the next decade, IMBeR’s mission is to, “Promote integrated marine research and enable capabilities for developing and implementing ocean sustainability options within and across the natural and social sciences, and communicate relevant information and knowledge needed by society to secure sustainable, productive and healthy oceans”. This Science Plan and Implementation Strategy provides a 10-year (2016-2025) marine research agenda for IMBeR. It is developed around three Grand Challenges (GC, see Graphical Executive Summary) focusing on climate variability, global change and drivers and stressors. The qualitative and quantitative understanding of historic and present ocean variability and change (Grand Challenge I) are the basis for scenarios, projections and predictions of the future (Grand Challenge II). These are linked in Grand Challenge III to understand how humans are causing the variability and changes, and how they, in turn, are impacted by these changes, including feedbacks between the human and ocean systems. Priority research areas with overarching and specific research questions are identified for each Grand Challenge. The Grand Challenges are supplemented with Innovation Challenges (IC, see graphical executive summary) that focus on new topics for IMBeR where research is needed and where it is believed that major achievements can be made within three to five years. The Innovation Challenges also provide a means for IMBeR to adjust its focus as major science discoveries are made and new priorities arise, especially regarding scientific innovations

eIMPACT-2 Cruise, RV Sarmiento de Gamboa

Oceanographic data acquired during the eIMPACT-2 Cruise (29SG20221108) on board the Research Vessel Sarmiento de Gamboa in 2022.The general objective of e-IMPACT is to study the linkage between the dynamics of mesoscale and sub-mesoscale processes occurring along the life history of cyclonic and anticyclonic eddies in the Canary Eddy Corridor (CEC), and their effects on the structure and metabolism of the planktonic community, as well as in their role in the vertical carbon flux to the deep ocean. e-IMPACT will address the coupled dynamics between food-web diversity and function, in relation to the physical and chemical conditions, the origin and composition of DOC and POC and their contribution to remineralization rates in the twilight zone of the ocean