Institut Universitaire Européen de la Mer

Microbes are dominant drivers of biogeochemical processes, yet drawing a global picture of functional diversity, microbial community structure, and their ecological determinants remains a grand challenge. We analyzed 7.2 terabases of metagenomic data from 243 Tara Oceans samples from 68 locations in epipelagic and mesopelagic waters across the globe to generate an ocean microbial reference gene catalog with >40 million nonredundant, mostly novel sequences from viruses, prokaryotes, and picoeukaryotes. Using 139 prokaryote-enriched samples, containing >35,000 species, we show vertical stratification with epipelagic community composition mostly driven by temperature rather than other environmental factors or geography. We identify ocean microbial core functionality and reveal that >73% of its abundance is shared with the human gut microbiome despite the physicochemical differences between these two ecosystems.

Marine plankton support global biological and geochemical processes. Surveys of their biodiversity have hitherto been geographically restricted and have not accounted for the full range of plankton size. We assessed eukaryotic diversity from 334 size-fractionated photic-zone plankton communities collected across tropical and temperate oceans during the circumglobal Tara Oceans expedition. We analyzed 18S ribosomal DNA sequences across the intermediate plankton-size spectrum from the smallest unicellular eukaryotes (protists, >0.8 micrometers) to small animals of a few millimeters. Eukaryotic ribosomal diversity saturated at ~150,000 operational taxonomic units, about one-third of which could not be assigned to known eukaryotic groups. Diversity emerged at all taxonomic levels, both within the groups comprising the ~11,200 cataloged morphospecies of eukaryotic plankton and among twice as many other deep-branching lineages of unappreciated importance in plankton ecology studies. Most eukaryotic plankton biodiversity belonged to heterotrophic protistan groups, particularly those known to be parasites or symbiotic hosts.

The net inputs of silicic acid (dissolved silica) to the world ocean have been revised to 6.1 +/- 2.0 teramoles of silicon per year (1 teramole = 10(12) moles). The major contribution (about 80 percent) comes from rivers, whose world average silicic acid concentration is 150 micromolar. These inputs are reasonably balanced by the net ouputs of biogenic silica of 7.1 +/- 1.8 teramoles of silicon per year in modern marine sediments. The gross production of biogenic silica (the transformation of dissolved silicate to particulate skeletal material) in surface waters was estimated to be 240 +/- 40 teramoles of silicon per year, and the preservation ratio (opal accumulation in sediment/gross production in surface waters) averages 3 percent. In the world ocean the residence time of silicon, relative to total biological uptake in surface waters, is about 400 years.

Decadal fluctuations in salinity, nutrients, chlorophyll, a variety of zooplankton taxa, and fish stocks in the Northeast Pacific are often poorly correlated with the most widely‐used index of large‐scale climate variability in the region ‐ the Pacific Decadal Oscillation (PDO). We define a new pattern of climate change, the North Pacific Gyre Oscillation (NPGO) and show that its variability is significantly correlated with previously unexplained fluctuations of salinity, nutrients and chlorophyll. Fluctuations in the NPGO are driven by regional and basin‐scale variations in wind‐driven upwelling and horizontal advection – the fundamental processes controlling salinity and nutrient concentrations. Nutrient fluctuations drive concomitant changes in phytoplankton concentrations, and may force similar variability in higher trophic levels. The NPGO thus provides a strong indicator of fluctuations in the mechanisms driving planktonic ecosystem dynamics. The NPGO pattern extends beyond the North Pacific and is part of a global‐scale mode of climate variability that is evident in global sea level trends and sea surface temperature. Therefore the amplification of the NPGO variance found in observations and in global warming simulations implies that the NPGO may play an increasingly important role in forcing global‐scale decadal changes in marine ecosystems.

Species interaction networks are shaped by abiotic and biotic factors. Here, as part of the Tara Oceans project, we studied the photic zone interactome using environmental factors and organismal abundance profiles and found that environmental factors are incomplete predictors of community structure. We found associations across plankton functional types and phylogenetic groups to be nonrandomly distributed on the network and driven by both local and global patterns. We identified interactions among grazers, primary producers, viruses, and (mainly parasitic) symbionts and validated network-generated hypotheses using microscopy to confirm symbiotic relationships. We have thus provided a resource to support further research on ocean food webs and integrating biological components into ocean models.

Over the past decade, a significant increase in the circulation of infectious agents was observed. With the spread and emergence of epizootics, zoonoses and epidemics, the risks of pandemics became more and more critical. Human and animal health has also been threatened by antimicrobial resistance, environmental pollution and the development of multifactorial and chronic diseases. This highlighted the increasing globalization of health risks and the importance of the human-animal-ecosystem interface in the evolution and emergence of pathogens. A better knowledge of causes and consequences of certain human activities, lifestyles and behaviors in ecosystems is crucial for a rigorous interpretation of disease dynamics and to drive public policies. As a global good, health security must be understood on a global scale and from a global and cross-cutting perspective, integrating human health, animal health, plant health, ecosystems health and biodiversity. In this paper, we discuss how crucial it is to consider ecological, evolutionary and environmental sciences in understanding the emergence and re-emergence of infectious diseases and in facing the challenges of antimicrobial resistance. We also discuss the application of the “One Health” concept to non-communicable chronic diseases linked to exposure to multiple stresses, including toxic stress, and new lifestyles. Finally, we draw up a list of barriers that need removing and the ambitions that we must nurture for the effective application of the “One Health” concept. We conclude that the success of this One Health concept now requires breaking down the interdisciplinary barriers that still separate human and veterinary medicine from ecological, evolutionary and environmental sciences. The development of integrative approaches should be promoted by linking the study of factors underlying stress responses to their consequences on ecosystem functioning and evolution. This knowledge is required for the development of novel control strategies inspired by environmental mechanisms leading to desired equilibrium and dynamics in healthy ecosystems and must provide in the near future a framework for more integrated operational initiatives.

Viruses influence ecosystems by modulating microbial population size, diversity, metabolic outputs, and gene flow. Here, we use quantitative double-stranded DNA (dsDNA) viral-fraction metagenomes (viromes) and whole viral community morphological data sets from 43 Tara Oceans expedition samples to assess viral community patterns and structure in the upper ocean. Protein cluster cataloging defined pelagic upper-ocean viral community pan and core gene sets and suggested that this sequence space is well-sampled. Analyses of viral protein clusters, populations, and morphology revealed biogeographic patterns whereby viral communities were passively transported on oceanic currents and locally structured by environmental conditions that affect host community structure. Together, these investigations establish a global ocean dsDNA viromic data set with analyses supporting the seed-bank hypothesis to explain how oceanic viral communities maintain high local diversity.

Over the past few decades, we have realized that the silica cycle is strongly intertwined with other major biogeochemical cycles, like those of carbon and nitrogen, and as such is intimately related to marine primary production, the efficiency of carbon export to the deep sea, and the inventory of carbon dioxide in the atmosphere. For nearly 20 years, the marine silica budget compiled by Tréguer et al. (1995) , with its exploration of reservoirs, processes, sources, and sinks in the silica cycle, has provided context and information fundamental to study of the silica cycle. Today, the budget needs revisiting to incorporate advances that have notably changed estimates of river and groundwater inputs to the ocean of dissolved silicon and easily dissolvable amorphous silica, inputs from the dissolution of terrestrial lithogenic silica in ocean margin sediments, reverse weathering removal fluxes, and outputs of biogenic silica (especially on ocean margins and in the form of nondiatomaceous biogenic silica). The resulting budget recognizes significantly higher input and output fluxes and notes that the recycling of silicon occurs mostly at the sediment-water interface and not during the sinking of silica particles through deep waters.

Although microplastics are known to pervade the global seafloor, the processes that control their dispersal and concentration in the deep sea remain largely unknown. Here, we show that thermohaline-driven currents, which build extensive seafloor sediment accumulations, can control the distribution of microplastics and create hotspots with the highest concentrations reported for any seafloor setting (190 pieces per 50 grams). Previous studies propose that microplastics are transported to the seafloor by vertical settling from surface accumulations; here, we demonstrate that the spatial distribution and ultimate fate of microplastics are strongly controlled by near-bed thermohaline currents (bottom currents). These currents are known to supply oxygen and nutrients to deep-sea benthos, suggesting that deep-sea biodiversity hotspots are also likely to be microplastic hotspots.

The cause and geodynamic impact of flat subduction are investigated. First, the 1500 km long Peru flat slab segment is examined. Earthquake hypocenter data image two morphologic highs in the subducting Nazca Plate which correlate with the positions of subducted oceanic plateaus. Travel time tomographic images confirm the three‐dimensional slab geometry and suggest a lithospheric tear may bound the NW edge of the flat slab segment, with possible slab detachment occurring down dip as well. Other flat slab regions worldwide are discussed: central Chile, Ecuador, NW Colombia, Costa Rica, Mexico, southern Alaska, SW Japan, and western New Guinea. Flat subduction is shown to be a widespread phenomenon, occuring in 10% of modern convergent margins. In nearly all these cases, as a spatial and temporal correlation is observed between subducting oceanic plateaus and flat subduction, we conclude that flat subduction is caused primarily by (1) the buoyancy of thickened oceanic crust of moderate to young age and (2) a delay in the basalt to eclogite transition due to the cool thermal structure of two overlapping lithospheres. A statistical analysis of seismicity along the entire length of the Andes demonstrates that seismic energy release in the upper plate at a distance of 250–800 km from the trench is on average 3–5 times greater above flat slab segments than for adjacent steep slab segments. We propose this is due to higher interplate coupling and the cold, strong rheology of the overriding lithosphere which thus enables stress and deformation to be transmitted hundreds of kilometers into the heart of the upper plate.

Abstract Chemical weathering is an integral part of both the rock and carbon cycles and is being affected by changes in land use, particularly as a result of agricultural practices such as tilling, mineral fertilization, or liming to adjust soil pH. These human activities have already altered the terrestrial chemical cycles and land‐ocean flux of major elements, although the extent remains difficult to quantify. When deployed on a grand scale, Enhanced Weathering (a form of mineral fertilization), the application of finely ground minerals over the land surface, could be used to remove CO 2 from the atmosphere. The release of cations during the dissolution of such silicate minerals would convert dissolved CO 2 to bicarbonate, increasing the alkalinity and pH of natural waters. Some products of mineral dissolution would precipitate in soils or be taken up by ecosystems, but a significant portion would be transported to the coastal zone and the open ocean, where the increase in alkalinity would partially counteract “ocean acidification” associated with the current marked increase in atmospheric CO 2 . Other elements released during this mineral dissolution, like Si, P, or K, could stimulate biological productivity, further helping to remove CO 2 from the atmosphere. On land, the terrestrial carbon pool would likely increase in response to Enhanced Weathering in areas where ecosystem growth rates are currently limited by one of the nutrients that would be released during mineral dissolution. In the ocean, the biological carbon pumps (which export organic matter and CaCO 3 to the deep ocean) may be altered by the resulting influx of nutrients and alkalinity to the ocean. This review merges current interdisciplinary knowledge about Enhanced Weathering, the processes involved, and the applicability as well as some of the consequences and risks of applying the method.

Research Article| June 01, 2000 Can slab melting be caused by flat subduction? Marc-André Gutscher; Marc-André Gutscher 1Laboratoire GTS, UMR 5573, Université Montpellier II, F-34095 Montpellier, France Search for other works by this author on: GSW Google Scholar René Maury; René Maury 2IUEM/Université Bretagne Occidentale, Place Nicolas Copernic, F-29280 Plouzané, France Search for other works by this author on: GSW Google Scholar Jean-Philippe Eissen; Jean-Philippe Eissen 3IRD Centre de Bretagne, B.P. 70, F-29280 Plouzané, France Search for other works by this author on: GSW Google Scholar Erwan Bourdon Erwan Bourdon 3IRD Centre de Bretagne, B.P. 70, F-29280 Plouzané, France Search for other works by this author on: GSW Google Scholar Author and Article Information Marc-André Gutscher 1Laboratoire GTS, UMR 5573, Université Montpellier II, F-34095 Montpellier, France René Maury 2IUEM/Université Bretagne Occidentale, Place Nicolas Copernic, F-29280 Plouzané, France Jean-Philippe Eissen 3IRD Centre de Bretagne, B.P. 70, F-29280 Plouzané, France Erwan Bourdon 3IRD Centre de Bretagne, B.P. 70, F-29280 Plouzané, France Publisher: Geological Society of America Received: 05 Oct 1999 Revision Received: 14 Mar 2000 Accepted: 28 Mar 2000 First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (2000) 28 (6): 535–538. https://doi.org/10.1130/0091-7613(2000)28<535:CSMBCB>2.0.CO;2 Article history Received: 05 Oct 1999 Revision Received: 14 Mar 2000 Accepted: 28 Mar 2000 First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Marc-André Gutscher, René Maury, Jean-Philippe Eissen, Erwan Bourdon; Can slab melting be caused by flat subduction?. Geology 2000;; 28 (6): 535–538. doi: https://doi.org/10.1130/0091-7613(2000)28<535:CSMBCB>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Slab melting has been suggested as a likely source of adakitic arc magmas (i.e., andesitic and dacitic magmas strongly depleted in Y and heavy rare earth elements). Existing numerical and petrologic models, however, restrict partial melting to very young (≤ 5 Ma) oceanic crust (typically at 60–80 km depth). Paradoxically, most of the known Pliocene-Quaternary adakite occurrences are related to subduction of 10–45 Ma lithosphere, which should not be able to melt under normal subduction-zone thermal gradients. We propose an unusual mode of subduction known as flat subduction, occurring in ∼10% of the world's convergent margins, that can produce the temperature and pressure conditions necessary for fusion of moderately old oceanic crust. Of the 10 known flat subduction regions worldwide, eight are linked to present or recent (<6 Ma) occurrences of adakitic magmas. Observations from Chile, Ecuador, and Costa Rica suggest a three-stage evolution: (1) steep subduction produces a narrow calc-alkaline arc, typically ∼300 km from the trench, above the asthenospheric wedge; (2) once flat subduction begins, the lower plate travels several hundred kilometers at nearly the same depth, thus remaining in a pressure-temperature window allowing slab melting over this broad distance; and (3) once flat subduction continues for several million years, the asthenospheric wedge disappears, and a volcanic gap results, as in modern-day central Chile or Peru. The proposed hypothesis, which reconciles thermal models with geochemical observations, has broad implications for the study of arc magmatism and for the thermal evolution of convergent margins. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Time series of environmental measurements are essential for detecting, measuring and understanding changes in the Earth system and its biological communities. Observational series have accumulated over the past 2-5 decades from measurements across the world's estuaries, bays, lagoons, inland seas and shelf waters influenced by runoff. We synthesize information contained in these time series to develop a global view of changes occurring in marine systems influenced by connectivity to land. Our review is organized around four themes: (i) human activities as drivers of change; (ii) variability of the climate system as a driver of change; (iii) successes, disappointments and challenges of managing change at the sea-land interface; and (iv) discoveries made from observations over time. Multidecadal time series reveal that many of the world's estuarine-coastal ecosystems are in a continuing state of change, and the pace of change is faster than we could have imagined a decade ago. Some have been transformed into novel ecosystems with habitats, biogeochemistry and biological communities outside the natural range of variability. Change takes many forms including linear and nonlinear trends, abrupt state changes and oscillations. The challenge of managing change is daunting in the coastal zone where diverse human pressures are concentrated and intersect with different responses to climate variability over land and over ocean basins. The pace of change in estuarine-coastal ecosystems will likely accelerate as the human population and economies continue to grow and as global climate change accelerates. Wise stewardship of the resources upon which we depend is critically dependent upon a continuing flow of information from observations to measure, understand and anticipate future changes along the world's coastlines.

In the EU, the mapping and assessment of ecosystems and their services, abbreviated to MAES, is seen as a key action for the advancement of biodiversity objectives, and also to inform the development and implementation of related policies on water, climate, agriculture, forest, marine and regional planning. In this study, we present the development of an analytical framework which ensures that consistent approaches are used throughout the EU. It is framed by a broad set of key policy questions and structured around a conceptual framework that links human societies and their well-being with the environment. Next, this framework is tested through four thematic pilot studies, including stakeholders and experts working at different scales and governance levels, which contributed indicators to assess the state of ecosystem services. Indicators were scored according to different criteria and assorted per ecosystem type and ecosystem services using the common international classification of ecosystem services (CICES) as typology. We concluded that there is potential to develop a first EU wide ecosystem assessment on the basis of existing data if they are combined in a creative way. However, substantial data gaps remain to be filled before a fully integrated and complete ecosystem assessment can be carried out.

The partial pressure of oxygen in Earth's atmosphere has increased dramatically through time, and this increase is thought to have occurred in two rapid steps at both ends of the Proterozoic Eon (∼2.5-0.543 Ga). However, the trajectory and mechanisms of Earth's oxygenation are still poorly constrained, and little is known regarding attendant changes in ocean ventilation and seafloor redox. We have a particularly poor understanding of ocean chemistry during the mid-Proterozoic (∼1.8-0.8 Ga). Given the coupling between redox-sensitive trace element cycles and planktonic productivity, various models for mid-Proterozoic ocean chemistry imply different effects on the biogeochemical cycling of major and trace nutrients, with potential ecological constraints on emerging eukaryotic life. Here, we exploit the differing redox behavior of molybdenum and chromium to provide constraints on seafloor redox evolution by coupling a large database of sedimentary metal enrichments to a mass balance model that includes spatially variant metal burial rates. We find that the metal enrichment record implies a Proterozoic deep ocean characterized by pervasive anoxia relative to the Phanerozoic (at least ∼30-40% of modern seafloor area) but a relatively small extent of euxinic (anoxic and sulfidic) seafloor (less than ∼1-10% of modern seafloor area). Our model suggests that the oceanic Mo reservoir is extremely sensitive to perturbations in the extent of sulfidic seafloor and that the record of Mo and chromium enrichments through time is consistent with the possibility of a Mo-N colimited marine biosphere during many periods of Earth's history.

Observations have shown that large areas of the world ocean are characterized by lower than expected chlorophyll concentrations given the ambient phosphate and nitrate levels. In these High Nutrient‐Low Chlorophyll regions, limitations of phytoplankton growth by other nutrients like silicate or iron have been hypothesized and further evidenced by in situ experiments. To explore these limitations, a nine‐component ecosystem model has been embedded in the Hamburg model of the oceanic carbon cycle (HAMOCC5). This model includes phosphate, silicate, dissolved iron, two phytoplankton size fractions (nanophytoplankton and diatoms), two zooplankton size fractions (microzooplankton and mesozooplankton), one detritus and semilabile dissolved organic matter. The model is able to reproduce the main characteristics of two of the three main HNLC areas, i.e., the Southern Ocean and the equatorial Pacific. In the subarctic Pacific, silicate and phosphate surface concentrations are largely underestimated because of deficiencies in ocean dynamics. The low chlorophyll concentrations in HNLC areas are explained by the traditional hypothesis of a simultaneous iron‐grazing limitation: Diatoms are limited by iron whereas nanophytoplankton is controlled by very efficient grazing by microzooplankton. Phytoplankton assimilates 18 × 10 9 mol Fe yr −1 of which 73% is supplied by regeneration within the euphotic zone. The model predicts that the ocean carries with it about 75% of the phytoplankton demand for new iron, assuming a 1% solubility for atmospheric iron. Finally, it is shown that a higher supply of iron to surface water leads to a higher export production but paradoxically to a lower primary productivity.

A common dynamical paradigm is that turbulence in the upper ocean is dominated by three classes of motion: mesoscale geostrophic eddies, internal waves and microscale three‐dimensional turbulence. Close to the ocean surface, however, a fourth class of turbulent motion is important: submesoscale frontal dynamics. These have a horizontal scale of O(1–10) km, a vertical scale of O(100) m, and a time scale of O(1) day. Here we review the physical‐chemical‐biological dynamics of submesoscale features, and discuss strategies for sampling them. Submesoscale fronts arise dynamically through nonlinear instabilities of the mesoscale currents. They are ephemeral, lasting only a few days after they are formed. Strong submesoscale vertical velocities can drive episodic nutrient pulses to the euphotic zone, and subduct organic carbon into the ocean's interior. The reduction of vertical mixing at submesoscale fronts can locally increase the mean time that photosynthetic organisms spend in the well‐lit euphotic layer and promote primary production. Horizontal stirring can create intense patchiness in planktonic species. Submesoscale dynamics therefore can change not only primary and export production, but also the structure and the functioning of the planktonic ecosystem. Because of their short time and space scales, sampling of submesoscale features requires new technologies and approaches. This paper presents a critical overview of current knowledge to focus attention and hopefully interest on the pressing scientific questions concerning these dynamics.

Research Article| December 01, 2002 Evidence for active subduction beneath Gibraltar M.-A. Gutscher; M.-A. Gutscher 1Institut Universitaire Europeen de la Mer, UMR 6538, Domaines Oceaniques, Plouzane, Brittany F-29280, France Search for other works by this author on: GSW Google Scholar J. Malod; J. Malod 1Institut Universitaire Europeen de la Mer, UMR 6538, Domaines Oceaniques, Plouzane, Brittany F-29280, France Search for other works by this author on: GSW Google Scholar J.-P. Rehault; J.-P. Rehault 1Institut Universitaire Europeen de la Mer, UMR 6538, Domaines Oceaniques, Plouzane, Brittany F-29280, France Search for other works by this author on: GSW Google Scholar I. Contrucci; I. Contrucci 1Institut Universitaire Europeen de la Mer, UMR 6538, Domaines Oceaniques, Plouzane, Brittany F-29280, France Search for other works by this author on: GSW Google Scholar F. Klingelhoefer; F. Klingelhoefer 2Bullard Laboratories, Cambridge University, Madingley Road, Cambridge CB3 0EZ, UK Search for other works by this author on: GSW Google Scholar L. Mendes-Victor; L. Mendes-Victor 3Institute of Earth Sciences, University of Lisbon, Rua de Escola Politecnica 58, Lisbon 1269-102, Portugal Search for other works by this author on: GSW Google Scholar W. Spakman W. Spakman 4Faculty of Earth Sciences, Utrecht University, Budapestlaan 4, Utrecht NL-3508, Netherlands Search for other works by this author on: GSW Google Scholar Author and Article Information M.-A. Gutscher 1Institut Universitaire Europeen de la Mer, UMR 6538, Domaines Oceaniques, Plouzane, Brittany F-29280, France J. Malod 1Institut Universitaire Europeen de la Mer, UMR 6538, Domaines Oceaniques, Plouzane, Brittany F-29280, France J.-P. Rehault 1Institut Universitaire Europeen de la Mer, UMR 6538, Domaines Oceaniques, Plouzane, Brittany F-29280, France I. Contrucci 1Institut Universitaire Europeen de la Mer, UMR 6538, Domaines Oceaniques, Plouzane, Brittany F-29280, France F. Klingelhoefer 2Bullard Laboratories, Cambridge University, Madingley Road, Cambridge CB3 0EZ, UK L. Mendes-Victor 3Institute of Earth Sciences, University of Lisbon, Rua de Escola Politecnica 58, Lisbon 1269-102, Portugal W. Spakman 4Faculty of Earth Sciences, Utrecht University, Budapestlaan 4, Utrecht NL-3508, Netherlands Publisher: Geological Society of America Received: 02 May 2002 Revision Received: 22 Aug 2002 Accepted: 24 Aug 2002 First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (2002) 30 (12): 1071–1074. https://doi.org/10.1130/0091-7613(2002)030<1071:EFASBG>2.0.CO;2 Article history Received: 02 May 2002 Revision Received: 22 Aug 2002 Accepted: 24 Aug 2002 First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation M.-A. Gutscher, J. Malod, J.-P. Rehault, I. Contrucci, F. Klingelhoefer, L. Mendes-Victor, W. Spakman; Evidence for active subduction beneath Gibraltar. Geology 2002;; 30 (12): 1071–1074. doi: https://doi.org/10.1130/0091-7613(2002)030<1071:EFASBG>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract We report on a marine seismic survey that images an active accretionary wedge west of Gibraltar. Ramp thrusts offset the seafloor and sole out to an east-dipping décollement, indicating ongoing westward-vergent tectonic shortening. New traveltime tomographic results image a slab of oceanic lithosphere descending from the Atlantic domain of the Gulf of Cadiz, passing through intermediate-depth (60–120 km) seismicity beneath the westernmost Alboran Sea, and merging with a region of deep-focus earthquakes 600–660 km below Granada, Spain. Together, these new data provide compelling evidence for an active east-dipping subduction zone. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Global trends in the occurrence, toxicity and risk posed by harmful algal blooms to natural systems, human health and coastal economies are poorly constrained, but are widely thought to be increasing due to climate change and nutrient pollution. Here, we conduct a statistical analysis on a global dataset extracted from the Harmful Algae Event Database and Ocean Biodiversity Information System for the period 1985-2018 to investigate temporal trends in the frequency and distribution of marine harmful algal blooms. We find no uniform global trend in the number of harmful algal events and their distribution over time, once data were adjusted for regional variations in monitoring effort. Varying and contrasting regional trends were driven by differences in bloom species, type and emergent impacts. Our findings suggest that intensified monitoring efforts associated with increased aquaculture production are responsible for the perceived increase in harmful algae events and that there is no empirical support for broad statements regarding increasing global trends. Instead, trends need to be considered regionally and at the species level.

The history of Eastern African hominids has been linked to a progressive increase of open grassland during the past 8 million years. This trend was explained by global climatic processes, which do not account for the massive uplift of eastern African topography that occurred during this period. Atmosphere and biosphere simulations quantify the role played by these tectonic events. The reduced topographic barrier before 8 million years ago permitted a zonal circulation with associated moisture transport and strong precipitation. Our results suggest that the uplift itself led to a drastic reorganization of atmospheric circulation, engendering the strong aridification and paleoenvironmental changes suggested by the data.