ALBERT

Description: Marine macrobenthic algae (or seaweeds), epiphytic microalgae, and other aquatic plants constitute the main food items of marine herbivorous fishes. About 5% of all fish species are herbivorous; only 30% of these are marine, most of them living in coral reefs. An analysis was performed on all the seaweeds that formed part of the natural diet of these fishes, based on information contained in FishBase (http://www.fishbase.org). The results showed that many coral-reef-associated marine herbivorous fishes, such as the families Blennidae, Kyphosidae and Siganidae, fed selectively on filamentous and turf fleshy seaweeds, which they prefer over calcareous coralline and encrusting species. In particular, Chlorophyceae of the genera Cladophora, Enteromorpha and Ulva were preferred by Scartichthys viridis (Blennidae), Girella spp. (Kyphosidae), Sarpa salpa (Sparidae), and Phaeophyceae in the genera Sargassum and Dictyota were preferred by Kyphosus spp. (Kyphosidae) and Siganus spp. (Siganidae). A web-based tool was developed to provide information on plants (algae, seagrasses, terrestrial plants and fruits) preferred as food by herbivorous fishes (http://www.incofish.org/herbitool.php). The tool is intended to assist aquaculturists, conservationists and ecosystem-based fisheries managers.

Description: We present a high-resolution (∼ 60–110 yr) multi-proxy record spanning Marine Isotope Stage 3 from IMAGES Core MD01-2378 (13°04.95′ S and 121°47.27′ E, 1783 m water depth), located in the Timor Sea, off NW Australia. Today, this area is influenced by the Intertropical Convergence Zone, which drives monsoonal winds during austral summer and by the main outflow of the Indonesian Throughflow, which represents a key component of the global thermohaline circulation system. Thus, this core is ideally situated to monitor the linkages between tropical and high latitude climate variability. Benthic δ18O data (Planulina wuellerstorfi) clearly reflect Antarctic warm events (A1–A4) as recorded by the EPICA Byrd and Dronning Maud Land ice cores. This southern high latitude signal is transferred by deep and intermediate water masses flowing northward from the Southern Ocean into the Indian Ocean. Planktonic δ18O shows closer affinity to northern high latitudes planktonic and ice core records, although only the longer-lasting Dansgaard–Oeschger warm events, 8, 12, 14, and 16–17 are clearly expressed in our record. This northern high latitude signal in the surface water is probably transmitted through atmospheric teleconnections and coupling of the Asian–Australian monsoon systems. Benthic foraminiferal census counts suggest a coupling of Antarctic cooling with carbon flux patterns in the Timor Sea. We relate increasing abundances of carbon-flux sensitive species at 38–45 ka to the northeastward migration of the West Australian Current frontal area. This water mass reorganization is also supported by concurrent decreases in Mg/Ca and planktonic δ18O values (Globigerinoides ruber white).

Description: The Storegga Slide, which occurred ∼8100 years ago, is one of the world's largest and best studied exposed submarine landslides. In this study we use novel geomorphometric techniques to constrain the submarine mass movements that have shaped the north-eastern Storegga Slide, understand the link between different forms of failure, and propose a revised development model for this region. According to this model, the north-eastern part of the Storegga Slide has developed in four major events. The first event (event 1) was triggered in water depths of 1500–2000 m. In this event, the surface sediments were removed by debris flows and turbidity currents, and deposited in the Norwegian Sea Basin. Loading of the seabed by sediments mobilised by the debris flows and turbidity currents resulted in the development of an evacuation structure. Loss of support associated with this evacuation structure, reactivation of old headwalls and seismic loading activated spreading in the failure surface of event 1 up to the main headwall (event 2). In some areas, spreading blocks have undergone high displacement and remoulding. Parts of the spreading morphology and the underlying sediment have been deformed or removed by numerous debris flows and turbidity currents (event 3). We suggest that the higher displacement and remoulding of the spreading blocks, and their removal by debris flows and turbidity currents, was influenced by increased pore pressures, possibly due to gas hydrate dissolution/dissociation or by lateral variability in the deposition of contourite drifts in palaoeslide scars. The fourth event entailed a large, blocky debris flow that caused localised compression and transpressive shearing in the southern part of the spreading area.

Description: We use new swath bathymetry data acquired during the RV Sonne cruise GEOPECO and complement them with swath data from adjacent regions to analyse the morphotectonics of the Peruvian convergent margin. The Nazca plate is not covered with sediments and therefore has a rough surface along the entire Peruvian trench. The styles of roughness differ significantly along the margin with linear morphological features trending in various directions, most of them oblique to the trench and roughness magnitudes of a few to several hundred meters. The lower slope is locally very rough and at the verge of failure throughout the entire Peruvian margin, as a result of subduction erosion causing the lower slope to over-steepen. Using curvature attributes to quantitatively examine the morphology in the Yaquina and Mendaña areas revealed that the latter shows a larger local roughness both seaward and landward of the trench. However, the amplitude of morphological roughness is larger in the Yaquina area. We identified a 125 km2 large slump on the Lima middle slope. Morphometric dating suggests an age of 74500 years within 35 to 40% error. Estimated incision rates on the upper slope are between 0.1 and 0.3 mm per year suggesting that landscape evolution on the Peruvian submarine continental slope is similarly slow than that in the Atacama desert.

Description: The submerged section of the North Anatolian fault within the Marmara Sea was investigated using acoustic techniques and submersible dives. Most gas emissions in the water column were found near the surface expression of known active faults. Gas emissions are unevenly distributed. The linear fault segment crossing the Central High and forming a seismic gap – as it has not ruptured since 1766, based on historical seismicity, exhibits relatively less gas emissions than the adjacent segments. In the eastern Sea of Marmara, active gas emissions are also found above a buried transtensional fault zone, which displayed micro-seismic activity after the 1999 events. Remarkably, this zone of gas emission extends westward all along the southern edge of Cinarcik basin, well beyond the zone where 1999 aftershocks were observed. The long term monitoring of gas seeps could hence be highly valuable for the understanding of the evolution of the fluid-fault coupling processes during the earthquake cycle within the Marmara Sea.

Description: Organic-rich sedimentary units called sapropels have formed repeatedly in the eastern Mediterranean Sea, in response to variations of solar radiation. Sapropel formation is due to a change either in the flux of organic matter to the sea floor from productivity changes or in preservation by bottom-water oxygen levels. However, the relative importance of surface-ocean productivity versus deep-water preservation for the formation of these organic-rich shale beds is still being debated, and conflicting interpretations are often invoked1, 2, 3, 4, 5, 6, 7. Here we analyse at high resolution the differences in the composition of the most recent sapropel, S1, in a suite of cores covering the entire eastern Mediterranean basin. We demonstrate that during the 4,000 years of sapropel formation, surface-water salinity was reduced and the deep eastern Mediterranean Sea, below 1,800 m depth, was devoid of oxygen. This resulted in the preferential basin-wide preservation of sapropel S1 with different characteristics above and below 1,800 m depth as a result of different redox conditions. We conclude that climate-induced stratification of the ocean may therefore contribute to enhanced preservation of organic matter in sapropels and potentially also in black shales.

Description: High-resolution seismic experiments, employing arrays of closely spaced, four-component ocean-bottom seismic recorders, were conducted at a site off western Svalbard and a site on the northern margin of the Storegga slide, off Norway to investigate how well seismic data can be used to determine the concentration of methane hydrate beneath the seabed. Data from P-waves and from S-waves generated by P–S conversion on reflection were inverted for P- and S-wave velocity (Vp and Vs), using 3D travel-time tomography, 2D ray-tracing inversion and 1D waveform inversion. At the NW Svalbard site, positive Vp anomalies above a sea-bottom-simulating reflector (BSR) indicate the presence of gas hydrate. A zone containing free gas up to 150-m thick, lying immediately beneath the BSR, is indicated by a large reduction in Vp without significant reduction in Vs. At the Storegga site, the lateral and vertical variation in Vp and Vs and the variation in amplitude and polarity of reflectors indicate a heterogeneous distribution of hydrate that is related to a stratigraphically mediated distribution of free gas beneath the BSR. Derivation of hydrate content from Vp and Vs was evaluated, using different models for how hydrate affects the seismic properties of the sediment host and different approaches for estimating the background-velocity of the sediment host. The error in the average Vp of an interval of 20-m thickness is about 2.5%, at 95% confidence, and yields a resolution of hydrate concentration of about 3%, if hydrate forms a connected framework, or about 7%, if it is both pore-filling and framework-forming. At NW Svalbard, in a zone about 90-m thick above the BSR, a Biot-theory-based method predicts hydrate concentrations of up to 11% of pore space, and an effective-medium-based method predicts concentrations of up to 6%, if hydrate forms a connected framework, or 12%, if hydrate is both pore-filling and framework-forming. At Storegga, hydrate concentrations of up to 10% or 20% were predicted, depending on the hydrate model, in a zone about 120-m thick above a BSR. With seismic techniques alone, we can only estimate with any confidence the average hydrate content of broad intervals containing more than one layer, not only because of the uncertainty in the layer-by-layer variation in lithology, but also because of the negative correlation in the errors of estimation of velocity between adjacent layers. In this investigation, an interval of about 20-m thickness (equivalent to between 2 and 5 layers in the model used for waveform inversion) was the smallest within which one could sensibly estimate the hydrate content. If lithological layering much thinner than 20-m thickness controls hydrate content, then hydrate concentrations within layers could significantly exceed or fall below the average values derived from seismic data.

Description: Overpressures measured with pore pressure penetrometers during Integrated Ocean Drilling Program (IODP) Expedition 308 reach 70% and 60% of the hydrostatic effective stress (View the MathML sourceλ*=(u−uh)(σvh')) in the first 200 meters below sea floor (mbsf) at Sites U1322 and U1324, respectively, in the deepwater Gulf of Mexico, offshore Louisiana. High overpressures are present within low permeability mudstones where there have been multiple, very large, submarine landslides during the Pleistocene. Beneath 200 mbsf at Site U1324, pore pressures drop significantly: there are no submarine landslides in this mixture of mudstone, siltstone, and sandstone. The penetrometer measurements did not reach the in situ pressure at the end of the deployment. We used a soil model to determine that an extrapolation approach based on the inverse of square route of time (View the MathML source1/t) requires much less decay time to achieve a desirable accuracy than an inverse time (1/t) extrapolation. Expedition 308 examined how rapid and asymmetric sedimentation above a permeable aquifer drives lateral fluid flow, extreme pore pressures, and submarine landslides. We interpret that the high overpressures observed are driven by rapid sedimentation of low permeability material from the ancestral Mississippi River. Reduced overpressure at depth at Site U1324 suggests lateral flow (drainage) whereas high overpressure at Site U1322 requires inflow from below: lateral flow in the underlying permeable aquifer provides one mechanism for these observations. High overpressure near the seafloor reduces slope stability and provides a mechanism for the large submarine landslides and low regional gradient (2°) offshore from the Mississippi delta.

Description: Ca isotope fractionation during inorganic calcite formation was experimentally studied by spontaneous precipitation at various precipitation rates (1.8 〈 log R 〈 4.4 μmol/m2/h) and temperatures (5, 25, and 40 °C) with traces of Sr using the CO2 diffusion technique. Results show that in analogy to Sr/Ca [see Tang J., Köhler S. J. and Dietzel M. (2008) Sr2+/Ca2+ and 44Ca/40Ca fractionation during inorganic calcite formation: I. Sr incorporation. Geochim. Cosmochim. Acta] the 44Ca/40Ca fractionation during calcite formation can be followed by the Surface Entrapment Model (SEMO). According to the SEMO calculations at isotopic equilibrium no fractionation occurs (i.e., the fractionation coefficient αcalcite-aq = (44Ca/40Ca)s/(44Ca/40Ca)aq = 1 and Δ44/40Cacalcite-aq = 0‰), whereas at disequilibrium 44Ca is fractionated in a primary surface layer (i.e., the surface entrapment factor of 44Ca, F44Ca 〈 1). As a crystal grows at disequilibrium, the surface-depleted 44Ca is entrapped into the newly formed crystal lattice. 44Ca depletion in calcite can be counteracted by ion diffusion within the surface region. Our experimental results show elevated 44Ca fractionation in calcite grown at high precipitation rates due to limited time for Ca isotope re-equilibration by ion diffusion. Elevated temperature results in an increase of 44Ca ion diffusion and less 44Ca fractionation in the surface region. Thus, it is predicted from the SEMO that an increase in temperature results in less 44Ca fractionation and the impact of precipitation rate on 44Ca fractionation is reduced. A highly significant positive linear relationship between absolute 44Ca/40Ca fractionation and the apparent Sr distribution coefficient during calcite formation according to the equation Δ44/40Cacalcite-aq=(−1.90±0.26)·logDSr−2.83±0.28is obtained from the experimental results at 5, 25, and 40 °C. Thus, Sr partitioning during calcite formation directly reflects Ca isotopic fractionation, independent of temperature, precipitation rate, and molar (Sr/Ca)aq ratio of the aqueous solution. If the (Sr/Ca)aq ratio is constant, Δ44/40Cacalcite-aq values can be directly followed by the Sr content of the precipitated calcite. A (Sr/Ca)aq ratio close to that of modern seawater yields the equation ... [View the MathML source]... Our experimental results indicate that neither precipitation rate nor temperature dominantly controls Ca isotope fractionation. However, Ca isotopes and Sr content of inorganic calcite comprise an excellent environmental multi-proxy in natural and applied systems.

Description: The electron backscattering diffraction technique (EBSD) was used to analyze bulging recrystallization microstructures from naturally and experimentally deformed quartz aggregates, both of which are characterized by porphyroclasts with finely serrated grain boundaries and grain boundary bulges set in a matrix of very fine recrystallized grains. For the Tonale mylonites we investigated, a temperature range of 300–380 °C, 0.25 GPa confining pressure, a flow stress range of ~ 0.1–0.2 GPa, and a strain rate of ~ 10− 13 s− 1 were estimated. Experimental samples of Black Hills quartzite were analyzed, which had been deformed in axial compression at 700 °C, 1.2–1.5 GPa confining pressure, a flow stress of ~ 0.3–0.4 GPa, a strain rate of ~ 10− 6 s− 1, and to 44% to 73% axial shortening. Using orientation imaging we investigated the dynamic recrystallization microstructures and discuss which processes may contribute to their development. Our results suggest that several deformation processes are important for the dismantling of the porphyroclasts and the formation of recrystallized grains. Grain boundary bulges are not only formed by local grain boundary migration, but they also display a lattice misorientation indicative of subgrain rotation. Dynamic recrystallization affects especially the rims of host porphyroclasts with a hard orientation, i.e. with an orientation unsuitable for easy basal slip. In addition, Dauphiné twins within porphyroclasts are preferred sites for recrystallization. We interpret large misorientation angles in the experimental samples, which increase with increasing strain, as formed by the activity of fluid-assisted grain boundary sliding.

Description: We consider the nonlinear dynamics of a long-term copepod (small crustaceans) time series sampled weekly in the Mediterranean sea from 1967 to 1992. Such population dynamics display a high variability that we consider here in an interdisciplinary study, using tools borrowed from the field of statistical physics. We analyse the extreme events of male and female abundances, and of the total population, and show that they both have heavy tailed probability density functions (pdf). We provide hyperbolic fits of the form p(x) ∼ 1/xμ+1, and estimate the value of μ using Hill’s estimator. We then study the ratio of male to female abundances, compared to the female abundances. Using conditional probability density functions and conditional averages, we show that this ratio is independent of the female density, when the latter is larger than a given threshold. This property is very useful for modelization. We also consider the product of male to female abundances, which can be ecologically related to the encounters. We show that this product is extremely intermittent, and link its pdf to the female pdf.

Description: Chemical changes associated with the rehydration of dry eclogites to form blueschists were studied to obtain information about the chemistry of the fluids infiltrating during this retrograde metamorphic overprint. The studied eclogites of the Tian Shan were formed during Carboniferous subduction of pillow basalts that show typical ocean island basalt geochemical signatures. The retrograde P–T path is characterised by decompression associated with cooling, typical for fragments of a subducting slab that are ascending in the cool and hydrated subduction channel. The fluids infiltrating the eclogites are interpreted to represent dehydration fluids of the down going slab that ascended to the overlying subduction channel. The rehydration of the eclogites proceeded from the pillow margins producing two concentric shells consisting of glaucophane-dominated blueschists (inner shell) and phengite–ankerite blueschists (outer shell) replacing omphacite and garnet of the eclogite. Mass-balance calculations based on major and trace element compositions of eclogites and blueschists point to high element mobility during fluid infiltration and associated metamorphic reactions. Blueschists show lower contents of REE, Y, Sr, Pb, U, P, Ca, Na, Al and Si compared to eclogites, indicating a loss of these elements, but they show higher contents of volatiles, Mg, transition metals and LILE, indicating a gain of these elements. The chemical changes point to a composition of the infiltrating fluid that has an affinity to fluids derived from serpentinites, i.e. with low concentrations in Si, Al, Ca and Na and high concentrations in Mg, Co and Ni. The gain of Cu, Mn, Zn and LILE in the blueschists points to an addition of a sediment-derived component in the serpentinite-derived fluid. The pronounced enrichment of K2O and of Ba at constant Ba/Th ratios in the blueschists resembles those of island arc basalts derived from a fluid-enriched source. The low element load of the fluid equilibrated with Mg-rich mélange zones induces the mobility of most of the elements during the eclogite–blueschist transformation to compensate for disequilibrium between the mafic rock and the infiltrating fluid. The associated volume loss enhances the fluid infiltration into the eclogite interior. Increasing precipitation rates and/or diminishing diffusion rates for element removal brought the eclogite–blueschist transformation to an end, which resulted in the preservation of eclogite in the pillow cores.

Description: The neodymium concentration, CNd, and isotopic composition, eNd, in seawater have been determined in the water column at five sites in the Barents Sea–Fram Strait area where most of the water exchange between the Arctic Ocean and the North Atlantic takes place. In the main Arctic Ocean inflow branch across the Barents Sea the concentration and isotopic composition (CNd = 15.5 pmol/kg and eNd = -10.8) are similar to those reported for the northeastern Nordic Seas, which is consistent with this region being a source area for the Arctic inflow. Due to the addition of Nd from Svalbard shelf sediments, the CNd in the surface waters above 150 m, in the Fram Strait inflow branch is higher by a factor of 2 and the eNd is shifted to lower values (-11.8). In the stratified Nansen Basin, where cold low salinity water overlies warmer Atlantic water the CNd and eNd do not vary with the vertical temperature–salinity structure but are essentially constant and similar to those of the Atlantic inflow throughout the entire water column, down to 3700 m depth, which indicates that the Nd is to a large extent of Atlantic origin. Compared to the Atlantic inflow water, the Nd in the major Arctic Ocean outflow, the Fram Strait, show higher CNd in the surface waters above 150 m, and a higher eNd (-9.8) throughout the entire water column down to 1300 m depth. Sources for the more radiogenic Nd isotopic composition in deep water of the Fram Strait outflow most likely involve boundary exchange with sediments on the shelf and slope as the water passes along the Canadian archipelago. River water is a possible source in the surface water but it also seems likely that Pacific water Nd, modified by interactions on the shelf, is an important component in the Fram Strait surface outflow. Changes in the relative proportions of inflow of river water and flow of Pacific water through the Arctic Ocean could thus influence the isotopic composition of Nd in the North Atlantic.

Description: In recent years several studies have shown that inducible resistance is ubiquitous in brown algae. However, while many studies on terrestrial plants identified eliciting signals and the response cascade to resistance, the knowledge on inducible marine macroalgal defense is lagging far behind and is often restricted to the mere recognition of its presence. This study is the first to accurately quantify the temporal dynamics, i.e. the time lag of induction and relaxation, of antifeeding defense in a marine macroalga, Fucus vesiculosus, from the Baltic Sea. Time lag of induction and reduction of induced feeding resistance were assessed via feeding assays, because the identities of defensive compounds are still unknown. Our results demonstrate that F vesiculosus induced defense 10-14 days after the onset of grazing by the isopod Idotea baltica. Defenses were relaxed within 2-4 days after cessation of grazing. Thus, defense seems to be deployed sparingly and just long enough to avoid substantial loss of tissue. (C) 2008 Elsevier B.V. All rights reserved.

Description: Diatoms are photosynthetic secondary endosymbionts found throughout marine and freshwater environments, and are believed to be responsible for around one-fifth of the primary productivity on Earth1, 2. The genome sequence of the marine centric diatom Thalassiosira pseudonana was recently reported, revealing a wealth of information about diatom biology3, 4, 5. Here we report the complete genome sequence of the pennate diatom Phaeodactylum tricornutum and compare it with that of T. pseudonana to clarify evolutionary origins, functional significance and ubiquity of these features throughout diatoms. In spite of the fact that the pennate and centric lineages have only been diverging for 90 million years, their genome structures are dramatically different and a substantial fraction of genes (approx40%) are not shared by these representatives of the two lineages. Analysis of molecular divergence compared with yeasts and metazoans reveals rapid rates of gene diversification in diatoms. Contributing factors include selective gene family expansions, differential losses and gains of genes and introns, and differential mobilization of transposable elements. Most significantly, we document the presence of hundreds of genes from bacteria. More than 300 of these gene transfers are found in both diatoms, attesting to their ancient origins, and many are likely to provide novel possibilities for metabolite management and for perception of environmental signals. These findings go a long way towards explaining the incredible diversity and success of the diatoms in contemporary oceans.

Description: The primary objective of this research is to understand the underlying mechanisms of the time-varying flux of carbon in the Sargasso Sea. To address this objective, a one-dimensional multi-component lower trophic level ecosystem model that includes detailed algal physiology as well as nutrient cycles is used at the Bermuda Atlantic Time-series Study (BATS, 31∘40′N31∘40′N, 64∘10′W64∘10′W) site. In this model autotrophic growth is represented by three algal groups and the cell quota approach is used to estimate algal growth and nutrient uptake. This model is tested and evaluated for year 1998 using the bimonthly BATS cruise data. Results show that phosphorus and dissolved organic matter (DOM) are necessary compartments to correctly simulate organic elemental cycles at the BATS site. Model results show that autotrophic eukaryotes and cyanobacteria (i.e. Prochlorococcus and Synechococcus) are the most abundant algal groups and are responsible for 63% and 33% of carbon production in the region, respectively. Sensitivity analyses show that the annual contribution of nitrogen fixation and atmospheric nitrogen deposition to new production is approximately 9% and 3%, respectively. However, the recycled nitrogen and phosphorus are important components of the ecosystem dynamics because sustained growth of algal groups depends on remineralized nutrients which accounts for 75% of the annual carbon production. Nutrient uptake and remineralization stoichiometry can play an important role in determining the surface ocean nutrient distribution. Model results suggest phosphate limitation even during the spring bloom. Phosphate may thus limit the growth of all algal groups throughout the year.

Description: The trophic position of Calanus finmarchicus in the Trondheim Fjord in 2004 was determined through stable isotope analyses. Wild specimens were sampled monthly in the fjord and δ13C and δ15N signatures of the developmental stages from CIII to adults were measured. There were statistically significant differences in the δ13C and δ15N signatures of three identified groups: overwintered parental generation, developing new generation and new generation preparing for overwintering. C. finmarchicus individuals raised in a laboratory on a pure algal diet (Dunaliella tertiolecta and Isochrysis galbana) provided stable isotope signatures for purely herbivorous copepods. With these signatures as comparison, the trophic position of C. finmarchicus in the Trondheim Fjord in 2004 was determined as trophic level 2.4, thus indicating omnivory under natural conditions. Additionally, our data suggest that seasonal differences in the δ13C signatures of C. finmarchicus are due to the varying lipid content of the different developmental stages.

Description: The effect of combined iron, silicate, and light co-limitation was investigated in the three diatom species Actinocyclus sp. Ehrenberg, Chaetoceros dichaeta Ehrenberg, and Chaetoceros debilis Cleve, isolated from the Southern Ocean (SO). Growth of all species was co-limited by iron and silicate, reflected in a significant increase in the number of cell divisions compared to the control. Lowest relative Si uptake and drastic frustule malformation was found under iron and silicate co-limitation in C. dichaeta, while Si limitation in general caused cell elongation in both Chaetoceros species. Higher light intensities similar to SO surface conditions showed a negative impact on growth of C. dichaeta and Actinocyclus sp. and no effect on C. debilis. This is in contrast to the assumed light limitation of SO diatoms due to deep wind driven mixing. Our results suggest that growth and species composition of Southern Ocean diatoms is influenced by a sensitive interaction of the abiotic factors, iron, silicate, and light.

Description: Drill cores obtained from Lake Petén Itzá, Petén, Guatemala, contain a ∼85-kyr record of terrestrial climate from lowland Central America that was used to reconstruct hydrologic changes in the northern Neotropics during the last glaciation. Sediments are composed of alternating clay and gypsum reflecting relatively wet and dry climate conditions, respectively. From ∼85 to 48 ka, sediments were dominated by carbonate clay indicating moist conditions during Marine Isotope Stages (MIS) 5a, 4, and early 3. The first gypsum layer was deposited at ∼48 ka, signifying a shift toward drier hydrologic conditions and the onset of wet–dry oscillations. During the latter part of MIS 3, Petén climate varied between wetter conditions during interstadials and drier states during stadials. The pattern of clay–gypsum (wet–dry) oscillations during the latter part of MIS 3 (∼48–23 ka) closely resembles the temperature records from Greenland ice cores and North Atlantic marine sediment cores and precipitation proxies from the Cariaco Basin. The most arid periods coincided with Heinrich Events when cold sea surface temperatures prevailed in the North Atlantic, meridional overturning circulation was reduced, and the Intertropical Convergence Zone (ITCZ) was displaced southward. A thick clay unit was deposited from 23 to 18 ka suggesting deposition in a deep lake, and pollen accumulated during the same period indicates vegetation consisted of a temperate pine-oak forest. This finding contradicts previous inferences that climate was arid during the Last Glacial Maximum (LGM) chronozone (21±2 ka). At ∼18 ka, Petén climate switched from moist to arid conditions and remained dry from 18 to 14.7 ka during the early deglaciation. Moister conditions prevailed during the warmer Bolling–Allerod (14.7–12.8 ka) with the exception of a brief return to dry conditions at ∼13.8 ka that coincides with the Older Dryas and meltwater pulse 1A. The onset of the Younger Dryas at 12.8 ka marked the return of gypsum and hence dry conditions. The lake continued to precipitate gypsum until ∼10.3 ka when rainfall increased markedly in the early Holocene.

Description: Observations show a significant intensification of the Southern Hemisphere westerlies, the prevailing winds between the latitudes of 30° and 60° S, over the past decades. A continuation of this intensification trend is projected by climate scenarios for the twenty-first century. The response of the Antarctic Circumpolar Current and the carbon sink in the Southern Ocean to changes in wind stress and surface buoyancy fluxes is under debate. Here we analyse the Argo network of profiling floats and historical oceanographic data to detect coherent hemispheric-scale warming and freshening trends that extend to depths of more than 1,000 m. The warming and freshening is partly related to changes in the properties of the water masses that make up the Antarctic Circumpolar Current, which are consistent with the anthropogenic changes in heat and freshwater fluxes suggested by climate models. However, we detect no increase in the tilt of the surfaces of equal density across the Antarctic Circumpolar Current, in contrast to coarse-resolution model studies. Our results imply that the transport in the Antarctic Circumpolar Current and meridional overturning in the Southern Ocean are insensitive to decadal changes in wind stress.

Description: Vertical profiles of chlorophyll concentration and phytoplankton biomass at ALOHA (HOT) are analyzed for the time period 1988 to 2004. Two different methods are applied: in the standard approach the data are averaged over depth horizons and in the alternative approach the profiles are shifted to the depth of the deepest subsurface maximum before averaging. The results show that the latter is the only meaningful way to look at vertical distribution patterns of both chlorophyll and phytoplankton in the oligotrophic ocean. In particular, a pronounced subsurface maximum of phytoplankton biomass appears only if this depth-adjustment method is used. Otherwise the vertical displacement of the subsurface biomass due to changes in the subsurface light field masks the actual signal: the thickness of the subsurface maximum is overestimated and the maximum is reduced. The results of this study have far-reaching consequences for the interpretation of the large number of profiles of chlorophyll and phytoplankton in the oligotrophic ocean. The absence of a subsurface biomass maximum might not be necessarily a result of photoacclimation but of inadequate analyses combined with coarse vertical resolution

Description: This study revisits the kinematics and tectonics of Central America subduction, synthesizing observations of marine bathymetry, high-resolution land topography, current plate motions, and the recent seismotectonic and magmatic history in this region. The inferred tectonic history implies that the Guatemala–El Salvador and Nicaraguan segments of this volcanic arc have been a region of significant arc tectonic extension; extension arising from the interplay between subduction roll-back of the Cocos Plate and the ~ 10–15mm/yr slower westward drift of the Caribbean plate relative to the North American Plate. The ages of belts of magmatic rocks paralleling both sides of the current Nicaraguan arc are consistent with long-term arc-normal extension in Nicaragua at the rate of ~ 5–10mm/yr, in agreement with rates predicted by plate kinematics. Significant arc-normal extension can ‘hide’ a very large intrusive arc-magma flux; we suggest that Nicaragua is, in fact, the most magmatically robust section of the Central American arc, and that the volume of intrusive volcanism here has been previously greatly underestimated. Yet, this flux is hidden by the persistent extension and sediment infill of the rifting basin in which the current arc sits. Observed geochemical differences between the Nicaraguan arc and its neighbors which suggest that Nicaragua has a higher rate of arc-magmatism are consistent with this interpretation. Smaller-amplitude, but similar systematic geochemical correlations between arc-chemistry and arc-extension in Guatemala show the same pattern as the even larger variations between the Nicaragua arc and its neighbors.

Description: Small (50e200 nm), calcium phosphate (apatite)-covered organic particles called nanobacteria or calcifying nanoparticles (CNP) seem to be ubiquitous in kidney stones and are thought to be involved in stone formation. Although initial claims that these particles are the smallest known life forms have been somewhat softened, much controversy remains as to their involvement in kidney stone formation as well as in other pathological calcifications. I suggest that such particles are non-living and may be formed during the normal living activities of bona-fide bacteria which inhabit the kidneys. This hypothesis is based on previous observations that bacteria immersed in a supersaturated fluid produce organic globules which calcify when released to the surrounding fluid, forming CNP-like particles. The possibility that this process is responsible for the formation of CNP associated with pathological calcifications deserves greater scrutiny.

Description: Recent discoveries demonstrate that the chemistry of arsenic in sulfidic waters is much more complex that previously believed. One implication is that all earlier thermodynamic data on stabilities of As thioanions require revision. Previously used experimental approaches for determining As thioanion stabilities may be inadequate to deal with the full range of complexity. Here we use computational as well as empirical information to construct a provisional model for equilibrium As thioanion distributions in sulfidic waters. Whereas previous authors have argued for either As(III) or As(V) thioanions, the new model predicts that both are important and can occur simultaneously under commonly encountered pH and ΣS−II conditions. At the order of magnitude level, the model reasonably predicts the solubility of As2S3 in sulfidic solutions, provides tentative peak assignments for published Raman spectroscopic data and plausibly accounts for how sulfide modifies the bacterial toxicity of As. The model yields a thermodynamic justification for how sulfide, which is usually regarded as a reducing agent, can counter-intuitively drive oxidation of As(III) to As(V), as has been observed both in the laboratory and in the field. Despite its uncertain accuracy, the model serves as a useful source of new, testable hypotheses about As geochemistry and highlights crucial experimental data needs.

Description: This chapter summarizes the efforts to use naturally occurring U- and Th-decay series nuclides as tracers of ocean circulation/mixing in open-ocean and coastal environments. The decay-series isotopes that have been exploited for ocean mixing studies are the four radium isotopes (226Ra, 228Ra, 224Ra, and 223Ra), 222Rn, and 227Ac. In addition, particle-reactive radionuclides (230Th, 231Pa, and 210Pb) have been used to constrain basin-wide water residence or ventilation times. Isotopes of radium, 222Rn, and 227Ac have been used to trace mixing and circulation in the ocean because of their relatively high solubility in seawater and suitable half-lives. 226Ra has a suitable radioactive mean-life, ∼2,300y, for large-scale oceanic mixing studies. The small-scale temporal and spatial variability generally associated with coastal mixing processes accentuates the integrating power of the 228Ra tracer. Along with the three other radium isotopes of the “radium quartet,” 228Ra is steadily input to coastal waters by desorption and diffusion from shelf, estuarine, and/or marsh sediments and through submarine groundwater discharge. Water close to the shore thus has a continual supply of these Ra isotopes despite their short decay lives. Produced in seawater by the decay of 226Ra, 222Rn in the ocean has activities equal to those of 226Ra except in regions of the air–sea and sediment–sea interfaces. Exceptionally high apparent vertical mixing has been observed in deep-ocean passages, where the interplay between strong bottom water flows, manganese nodule occurrence, and high standing crop of excess 222Rn is much in evidence. Several studies have explored the use of 227Ac for tracing basin-wide circulation and mixing on decadal time-scales. The potential of 227Ac as a tracer appears to lie chiefly in assessing diapycnal mixing in the deep sea.

Description: In two closely spaced moorings in the Kiel Bight, four different current meterstwo rotor current meters (Aanderaa and Vector averaging), an acoustic current meter (designed by Gytre), and a pendulum current meter (designed by Niskin) were moored for 22 days. The Vector averaging current meter (VACM) was used as reference instrument on one mooring with the floatation at 7 m depth. The floatation of the second mooring was at 5 m depth in the first 17 days of the experiment, but in 2.7 m depth in the last 5 days to make their mooring more effected by surface waves. The Niskin wing current meter was most effected by wave-induced mooring motion. The Gytre instrument showed the smallest surface-wave effects. The vector variances of this instrument in 7.4 m depth on the surface-wave effected mooring and those of the VACM in 10 m depth on the reference mooring were about equal.

Description: Glass separates from 115 ash layers derived from the Kamchatkan (DSDP Site 192; 34 layers), the eastern Aleutian (DSDP Site 183; 56 layers) and the Alaska Peninsula (DSDP Site 178; 25 layers) volcanic arcs have been analyzed for up to 28 elements. In addition, the abundance and diversity of associated mafic phenocrysts have been evaluated. The resulting data set has made possible an evaluation of the late Miocene to Recent changes in composition of ashes derived from North Pacific volcanic arcs and of the factors controlling the evolution of highly siliceous magmas. We find no evidence for a general transition from arc tholeiite to calc-alkalic magma parentage of ashes derived from the volcanic arcs during the last 10 m.y., but instead find 0.1- to 0.5-m.y. intervals during which particular types of volcanism are prevalent. Most convincing is the transition from arc tholeiite to calc-alkalic for ashes derived from Kamchatka during the last 0.8 m.y., a change believed to be associated with a landward shift in the site of magma generation. Considered together, ashes derived from North Pacific volcanic arcs have been becoming more siliceous during the last 1.5 m.y. and may be associated with accelerated subduction during the same time interval. Hydrous phenocrysts (e.g., biotite) are typically associated with low-silica deep-sea ashes, but not with terrestrial volcanic rocks of comparable silica contents, suggesting the important role of water in the evolution of siliceous magma. REE patterns and relative abundances of mafic phenocrysts demonstrate the importance of fractional crystallization in controlling the evolution of highly siliceous arc magmas. REE increase with increasing silica, but become less concentrated in ashes with SiO2 〉 64%. Eu anomalies increase throughout the SiO2 range. Initial fractionation is dominated by clinopyroxene and plagioclase with amphibole strongly influencing fractionation above 64% SiO2.

Description: This study focuses on the Carboniferous sediments of the Karawanken Mountains (Austria/Slovenia) to identify possible source areas and their geotectonic setting. Provenance analyses have been applied using petrographical and geochemical approaches what also lead to an evaluation of the used methods. Within the Hochwipfel Formation five stratigraphic related petrofacies groups can be defined using the sandstone component inventory. Homogenous provenance results based on major element and trace element data suggest an active continental margin/continental island arc with probably an intraplate signature. Provenance analyses of light minerals point to source areas with basement rocks (mainly metamorphic), arc material and sedimentary rocks. In combination, the rapid and highly variable change of provenance signatures within the stratigraphic succession of the petrofacies types excludes a single provenance in the western part of the Karawanken Mountains. Additionally, changes in composition of the individual petrofacies groups correlate with the stratigraphy in the eastern part. Varying contents of garnet, chromite, hornblende and epidote, within the sedimentary succession of the Hochwipfel sandstones, can partly be attributed to geodynamical changes in the hinterland. The chemical compositions of garnets, tourmalines, and chromites, confirm the results of both geochemistry and sediment petrography. In a quantitative approach based on petrography we can see an equal mixture of all source areas, whereas quantification with a geochemical approach results in c. 11% of material that can be attributed to a passive continental margin source, 28 to 37% to an active continental margin, c. 44% to a magmatic arc setting and 16 to 19% to an oceanic within-plate source area. The resulting model for the geodynamical setting of the Hochwipfel basin during the Late Palaeozoic can be best explained by a forearc basin in the eastern part and various pull-apart basins in the western part, connected through bypasses, at the continental margin of Gondwana and the Palaeotethys. As an additional outcome this study clarifies, that geochemically derived provenance results, based on bulk-rock and mineral composition, recognize best complex geodynamical settings and a mixture of sources since they incorporate best the provenance significant lithic components. On the other hand it points out that an application of additional petrological approaches does not necessarily lead to further information and an elimination of errors but could be essential to define general information of the investigated stratigraphy, like the correlation of deposits with stratigraphy (petrofacies groups).

Description: Zooxanthellate scleractinian corals are known as archives for temporal variations of climate variables, such as sea surface temperature, salinity or productivity. The use of azooxanthellate cold-water corals as potential archives for intermediate water mass properties and climate variability was tested recently. However, the correlation of established proxies such as delta O-18 and delta C-13 with temperature is difficult since there is no direct temperature equation applicable as in shallow-water corals. Other temperature proxies such as Sr/Ca, Mg/Ca and U/Ca are influenced by the complex microstructure of the aragonite skeleton, the rate of calcification, and other vital effects observed for coral species. For the first time we show that the stable strontium isotope ratio delta Sr-88/86 incorporated in the skeletons of the cold-water coral species Lophelia pertusa portrays the ambient seawater temperature. The temperature sensitivity from live samples collected along the European continental margin covering a temperature range from 6 degrees to 10 degrees C is 0.026 +/- 0.003%omicron/degrees C (2 sigma standard error) which is a sensitivity similar to the tropical shallow-water coral record of Pavona clavata. This indicates a similar fractionation process of strontium for both, zooxanthellate and azooxanthellate corals. For coral aragonite the delta Sr-88/86 ratio may serve as a new paleo-temperature proxy and introduces new perspectives in paleoceanography with respect to intermediate water dynamics.

Description: We compare several statistical routines that may be used to calculate delta O-18 and SSS from paired coral Sr/Ca and delta O-18 measurements. Typically, the delta O-18(coral)-SST relationship is estimated by linear regression of coral delta O-18 vs. SST. If this method is applied, evidence should be given that at a particular site SST and SSS do not co-vary. In the tropical oceans, SST and delta O-18(sw) (SSS) often co-vary, and this will bias the estimate of the regression slope of delta O-18(coral)-SST. Using a stochastic model, we show that covariance leads to a bias in the coefficients of the univariate regression equations. As the slope of the delta O-18(coral)-SST relationship has known, we propose to insert this value for gamma(1) in the regression models. This requires that the constants of the regression equations are removed. To omit the constants, we propose to center the regression equations (i.e., to remove the mean values from the variables). The statistical error propagation is calculated to assess our ability to resolve past variations in delta O-18(sw) (SSS). At Tahiti, we find that the combined analytical uncertainties of coral delta O-18 and Sr/Ca equal the amplitude of the seasonal cycle of delta O-18(sw) (SSS). Therefore, we cannot resolve the seasonal cycle of SSS at Tahiti. At Timor, the error of reconstructed delta O-18(sw) (SSS) is lower than the magnitude of seasonal variations of delta O-18(sw) (SSS), and the seasonal cycle of delta O-18(sw) (SSS) can be resolved. (c) 2008 Elsevier Ltd. All rights reserved.

Description: Rising levels of atmospheric carbon dioxide lead to acidification of the oceans. A site in the Mediterranean, naturally carbonated by under-sea volcanoes, provides clues to the possible effects on marine ecosystems.

Description: Melt inclusions in olivine are source of unique information about primitive mantle melts. Here we report results of an experimental study aimed at evaluating the ability of olivine to isolate chemically melt inclusions from the host magma after their entrapment. We demonstrate that nearly ‘dry’ melt inclusions from Galapagos Plateau basalt can gain up to 2.5 wt.% of water if they are placed for 2 days in a water-bearing melt at 200 MPa and 1140 °C. The major element composition of melt inclusions also changed significantly, as a result of a re-equilibration with the olivine host mineral, whereas no significant changes were detected for incompatible trace elements. Our results indicate that inclusions in olivine can rapidly and selectively exchange water with the matrix melt, probably, through combination of proton diffusion and molecular water transport along dislocations in olivine. The fast water transport explains element fractionation, which is not predictable from the theory of magmatic processes. An efficient re-equilibration of melt inclusions with matrix melt can explain the decoupling of water and incompatible trace elements (e.g., H2O vs. K2O) reported for suites of primitive inclusions from mid-ocean-ridge setting and island arcs. Rare cases of well preservation of initial water content in suites of co-genetic inclusions imply very short residence time (a few hours) of the olivine phenocrysts in magma with contrasting water content during fractionation and transport to the surface and rapid quenching upon eruption

Description: Chemoherm carbonates, as well as numerous other types of methane seep carbonates, were discovered in 2004 along the passive margin of the northern South China Sea. Lithologically, the carbonates are micritic containing peloids, clasts and clam fragments. Some are highly brecciated with aragonite layers of varying thicknesses lining fractures and voids. Dissolution and replacement is common. Mineralogically, the carbonates are dominated by high magnesium calcites (HMC) and aragonite. Some HMCs with MgCO3 contents of between 30–38 mol%–extreme-HMC, occur in association with minor amounts of dolomite. All of the carbonates are strongly depleted in δ13C, with a range from − 35.7 to − 57.5‰ PDB and enriched in δ18O (+ 4.0 to + 5.3‰ PDB). Abundant microbial rods and filaments were recognized within the carbonate matrix as well as aragonite cements, likely fossils of chemosynthetic microbes involved in carbonate formation. The microbial structures are intimately associated with mineral grains. Some carbonate mineral grains resemble microbes. The isotope characteristics, the fabrics, the microbial structure, and the mineralogies are diagnostic of carbonates derived from anaerobic oxidation of methane mediated by microbes. From the succession of HMCs, extreme-HMC, and dolomite in layered tubular carbonates, combined with the presence of microbial structure and diagenetic fabric, we suggest that extreme-HMC may eventually transform into dolomites. Our results add to the worldwide record of seep carbonates and establish for the first time the exact locations and seafloor morphology where such carbonates formed in the South China Sea. Characteristics of the complex fabric demonstrate how seep carbonates may be used as archives recording multiple fluid regimes, dissolution, and early transformation events.

Description: We present new major and trace element and O–Sr–Nd-isotope data for igneous rocks from the western Mediterranean Alborán Sea, collected during the METEOR 51/1 cruise, and for high-grade schists and gneisses from the continental Alborán basement, drilled during the Ocean Drilling Programme (ODP Leg 161, Site 976). The geochemical data allow a detailed examination of crustal and mantle processes involved in the petrogenesis of the lavas and for the first time reveal a zonation of the Miocene Alborán Sea volcanism: (1) a keel-shaped area of LREE-depleted (mainly tholeiitic series) lavas in the central Alborán Sea, generated by high degrees of partial melting of a depleted mantle source and involving hydrous fluids from subducted marine sediments, that is surrounded by (2) a horseshoe-shaped zone with LREE-enriched (mainly calc-alkaline series) lavas subparallel to the arcuate Betic-Gibraltar-Rif mountain belt. We propose that the geochemical zonation of the Miocene Alborán Basin volcanism results from eastward subduction of Tethys oceanic lithosphere coupled with increasing lithospheric thickness between the central Alborán Sea and the continental margins of Iberia and Africa.

Description: In our searching program for bioactive secondary metabolites from marine Streptomycetes, three microbial benzopyrone derivatives (1–3), 7-methylcoumarin (1) and two flavonoides, rhamnazin (2) and cirsimaritin (3), were obtained during the working up of the ethyl acetate fraction of a marine Streptomyces fusant obtained from protoplast fusion between Streptomyces strains Merv 1996 and Merv 7409. The structures of the three compounds (1–3) were established by nuclear magnetic resonance, mass, UV spectra, and by comparison with literature data. Marine Streptomyces strains were identified based on their phenotypic and chemotypic characteristics as two different bioactive strains of the genus Streptomyces. We described here the fermentation, isolation, as well as the biological activity of these bioactive compounds. The isolated compounds (1–3) are reported here as microbial products for the first time.

Description: Upwelling is a typical phenomenon of the Baltic Sea. Because the Baltic Sea is a semi- enclosed basin, winds from favorable directions blowing predominately parallel to the coast cause upwelling leading to vertical displacement of the water body and mixing. During the thermal stratified period, upwelling can lead to a strong sea-surface temperature drop of more than 10 °C changing drastically the thermal balance and stability conditions at the sea-surface. Upwelling can play a key role in replenishing the euphotic zone with the nutritional components necessary for biological productivity when the surface layer is depleted of nutrients. Consequently, it has been found out that in such areas where upwelling lifts phosphorus-rich deep water to the surface, the N/P ratio becomes low which favors the blooming of nitrogen-fixing blue-green algae. The rapid temperature decrease during such events was recognized and documented a long time ago when temperature measurements became available. Thus, the study of the upwelling process has a long tradition. However, although the importance of upwelling has generally been accepted for the Baltic Sea, no general review of upwelling exists. The objective of this paper is a comprehensive review of the upwelling process, its dynamics and reflections to ecosystem processes in the Baltic Sea using all relevant literature which will help to close the gaps of present knowledge and some recommendations for future work are outlined accordingly.

Description: During segment-scale studies of the southern Mid-Atlantic Ridge (MAR), 7–12° S, we found evidence in the water column for high-temperature hydrothermal activity, off-axis, east of Ascension Island. Extensive water column and seafloor work using both standard CTD and deep submergence AUV and ROV deployments led to the discovery and sampling of the “Drachenschlund” (“Dragon Throat”) black smoker vent at 8°17.87′ S/13°30.45′ W in 2915 m water depth. The vent is flanked by several inactive chimney structures in a field we have named “Nibelungen”. The site is located 6 km south of a non-transform offset between two adjacent 2nd-order ridge-segments and 9 km east of the presently-active, northward-propagating A2 ridge-segment, on a prominent outward-facing fault scarp. Both vent-fluid compositions and host-rock analyses show this site to be an ultramafic-hosted system, the first of its kind to be found on the southern MAR. The thermal output of this single vent, based on plume rise-height information, is estimated to be 60 ± 15 MW. This value is high for a single “black smoker” vent but small for an entire field. The tectonic setting and low He content of the vent fluids imply that high-temperature off-axis venting at “Drachenschlund” is driven not by magmatic processes, as at the majority of on-axis hydrothermal systems, but by residual heat “mined” from the deeper lithosphere. Whether this heat is being extracted from high-temperature mantle peridotites or deep crustal cumulates formed at the “duelling” non-transfrom offset is unclear, in either case the Drachenschlund vent provides the first direct observations of how cooling of deeper parts of the lithosphere, at least at slow-spreading ridges, may be occurring.

Description: High frequency sampling was performed in daylight hours along a 35 km transect in the Ligurian Sea to investigate the upper layer zooplankton distribution during the spring phytoplankton bloom. The results show detailed spatial structure and biomass of key zooplankton functional groups, copepods, salps and krill larvae, within the different water masses characterizing this region. Although observed values of total copepod biomass distribution were rather constant along the transect, species-specific patterns were observed in the copepod spatial distribution. The larger species Calanus helgolandicus, as well as Centropages typicus, Oithona spp., and Oncaea spp., were associated with the frontal zone. However, Acartia spp. had a scattered distribution, and Clausocalanus/Paracalanus did not have a clear pattern. In addition, krill larvae were concentrated in the frontal area and salps had a scattered pattern. The cross-shore zooplankton distribution appeared strongly influenced by both the Northern Ligurian current governing inshore waters, which acts as a major flushing forcing, and the Ligurian front, which governs offshore waters and may act as retention area for zooplankton.

Description: We examine the micro-earthquake seismicity recorded by two temporary arrays of ocean bottom seismometers on the outer rise offshore southern Chile on young oceanic plate of ages 14 Ma and 6 Ma, respectively. The arrays were in operation from December 2004–January 2005 and consisted of 17 instruments and 12 instruments, respectively. Approximately 10 locatable events per day were recorded by each of the arrays. The catalogue, which is complete for magnitudes above 1.2–1.5, is characterized by a high b value, i.e., a high ratio of small to large events, and the data set is remarkable in that a large proportion of the events form clusters whose members show a high degree of waveform similarity. The largest cluster thus identified consisted of 27 similar events (average inter-event correlation coefficient 〉 0.8 for a 9.5 s window), and waveform similarity persists far into the coda. Inter-event spacing is irregular, but very short waiting times of a few minutes are far more common than expected from a Poisson distribution. Seismicity with these features (high b value, large number of similar events with short waiting times) is typical of swarm activity, which, based on empirical evidence and theoretical considerations, is generally thought to be driven by fluid pressure variations. Because no pronounced outer rise bulge exists on the very young plate in the study region, it is unlikely that melt is accessible from decompression melting or opening of cracks. A fluid source related to processes at the nearby ridge is conceivable for the younger segment but less likely for the older one. We infer that the fluid source could be seawater, which enters through fractures in the crust. Most of the similar-earthquake clusters are within the crust, but some of them locate significantly below the Moho. If our interpretation is correct, this implies that water is present within the mantle. Hydration of the mantle is also indicated by a decrease of Pn velocities below the outer rise seen on a refraction profile through one of the arrays [Contreras-Reyes, E., Grevemeyer, I., Flueh, E.R., Scherwath, M., Heesemann, M., 2007. Alteration of the subducting oceanic lithosphere at the southern central Chile trench-outer rise. Geochem., Geophys. Geosyst. 8, Q07003.]. The deepest events within the array on the 6 Ma old plate occur where the temperature reaches 500–600 °C, consistent with the value observed for large intraplate earthquakes within the mantle (650 °C), suggesting that the maximum temperature at which these fluid-mediated micro-earthquakes can occur is similar or identical to that of large earthquakes.

Description: The mean available potential energy released by baroclinic instability into the meso-scale eddy field has to be dissipated in some way and Tandon and Garrett [Tandon, A., Garrett, C., 1996. On a recent parameterization of mesoscale eddies. J. Phys. Oceanogr. 26 (3), 406–416] suggested that this dissipation could ultimately involve irreversible mixing of buoyancy by molecular processes at the small-scale end of the turbulence cascade. We revisit this idea and argue that the presence of dissipation within the thermocline automatically requires that a component of the eddy flux associated with meso-scale eddies must be associated with irreversible mixing of buoyancy within the thermocline. We offer a parameterisation of the implied diapycnal diffusivity based on (i) the dissipation rate for eddy kinetic energy given by the meso-scale eddy closure of Eden and Greatbatch [Eden, C., Greatbatch, R.J., 2008. Towards a meso-scale eddy closure. Ocean Modell. 20, 223–239.] and (ii) a fixed mixing efficiency. The implied eddy-induced diapycnal diffusivity (κ) is implemented in a coarse resolution model of the North Atlantic. In contrast to the vertical diffusivity given by a standard vertical mixing scheme, large lateral inhomogeneities can be found for κ in the interior of the ocean. In general, κ is large, i.e. up to o(10) cm2/s, near the western boundaries and almost vanishing in the interior of the ocean.

Description: Integrated interpretation of multi-beam bathymetric, sediment-penetrating acoustic (PARASOUND) and seismic data show a multiple slope failure on the northern European continental margin, north of Spitsbergen. The first slide event occurred during MIS 3 around 30 cal. ka BP and was characterised by highly dynamic and rapid evacuation of ca. 1250 km3 of sediment from the lower to the upper part of the continental slope. During this event, headwalls up to 1600 m high were created and ca. 1150 km3 material from hemi-pelagic sediments and from the lower pre-existing trough mouth fan has been entrained and transported into the semi-enclosed Sophia Basin. This megaslide event was followed by a secondary evacuation of material to the Nansen Basin by funnelling of the debris through the channel between Polarstern Seamount and the adjacent continental slope. The main slide debris is overlain by a set of fining-upward sequences as evidence for the associated suspension cloud and following minor failure events. Subsequent adjustment of the eastern headwalls led to failure of rather soft sediments and creation of smaller debris flows that followed the main slide surficial topography. Discharge of the Hinlopen ice stream during the Last Glacial Maximum and the following deglaciation draped the central headwalls and created a fan deposit of glacigenic debris flows.

Description: A simplified version of a kinetic–bioenergetic reaction model for anaerobic oxidation of methane (AOM) in marine sediments [Dale, A.W., Regnier, P., Van Cappellen, P., 2006. Bioenergetic controls on anaerobic oxidation of methane (AOM) in coastal marine sediments: a theoretical analysis. Am. J. Sci. 306, 246–294.] is used to assess the impact of transport processes on biomass distributions, AOM rates and methane release fluxes from the sea floor. The model explicitly represents the functional microbial groups and the kinetic and bioenergetic limitations of the microbial metabolic pathways involved in AOM. Model simulations illustrate the dominant control exerted by the transport regime on the activity and abundance of AOM communities. Upward fluid flow at active seep systems restricts AOM to a narrow subsurface reaction zone and sustains high rates of methane oxidation. In contrast, pore-water transport dominated by molecular diffusion leads to deeper and broader zones of AOM, characterized by much lower rates and biomasses. Under steady-state conditions, less than 1% of the upward dissolved methane flux reaches the water column, irrespective of the transport regime. However, a sudden increase in the advective flux of dissolved methane, for example as a result of the destabilization of methane hydrates, causes a transient efflux of methane from the sediment. The benthic efflux of dissolved methane is due to the slow growth kinetics of the AOM community and lasts on the order of 60 years. This time window is likely too short to allow for a significant escape of pore-water methane following a large scale gas hydrate dissolution event such as the one that may have accompanied the Paleocene/Eocene Thermal Maximum (PETM).

Description: We employed a coupled biological–physical, individual-based model (IBM) to estimate spatial and temporal changes in larval fish habitat suitability (the potential for areas to support survival and high rates of growth) of the German Bight, southern North Sea. In this Lagrangian approach, larvae were released into a size-structured prey field that was constructed from in situ measurements of the abundance and prosome lengths of stages of three copepods (Acartia spp., Temora longicornis, Pseudocalanus elongatus) collected on a station grid repeatedly sampled from February to October 2004. The choice of prey species and the model parameterisations for larval fish foraging and growth were based on field data collected for sprat (Sprattus sprattus) and other clupeid larvae. A series of 10-day simulations were conducted using 20 release locations to quantify spatial–temporal differences in projected larval sprat growth rates (mm d− 1) for mid-April, mid-May and mid-June 2004. Based upon an optimal foraging approach, modeled sprat growth rates agreed well with those measured in situ using larval fish ototliths. On the German GLOBEC station grid, our model predicted areas that were mostly unsuitable habitats (areas of low growth potential), e.g. north of the Frisian Islands, and others that were consistently suitable habitats (areas that had high growth potential), e.g. in the inner German Bight. In some instances, modelled larvae responded rapidly (~ 5 days) to changing environmental characteristics experienced along their drift trajectory, a result that appears reasonable given the dynamic nature of frontal regions such as our study area in the southern North Sea.

Description: An ancient hydrocarbon seep province of 14 isolated, authigenic carbonate deposits has been identified in fine-grained, deep-marine siliciclastic strata of the Miocene East Coast Basin, North Island, New Zealand. These forearc sediments have been uplifted and complexly deformed into accretionary ridges, adjacent to the still-active Hikurangi convergent margin. Older active and passive margin strata (mid-Cretaceous to Oligocene in age) underlie the Neogene sequence, and contain oil- and gas-prone source rocks. Older Mesozoic meta-sedimentary rocks constitute the backstop against which the current phase of subduction-related sedimentation has accumulated (~ 24 Ma–present). The seep-carbonates (up to 10 m thick, 200 m across) archive methane signatures in their depleted carbon isotopes (to δ13C –51.7‰ PDB), and contain chemosynthesis-based paleocommunities (e.g. worm tubes, bathymodioline mussels, and vesicomyid, lucinid and thyasirid bivalves) typical of other Cenozoic and modern seeps. Northern and southern sites are geographically separated, and exhibit distinct lithological and faunal differences. Structural settings are variable. Seep-associated lithologies also are varied, and suggest carbonate development in sub-seafloor, seafloor and physically reworked (diapiric expansion, gas explosion, gravity slide or debris flow) settings, similar to Italian Apennine seep deposits of overlapping ages. Peculiar attributes of the New Zealand Miocene seep deposits are several, including digitate thrombolites of clotted microbial micrite encased in thick, isopachous horizons and botryoids of aragonite. Seep plumbing features are also well-exposed at some sites, displaying probable gas-explosion breccias filled with aragonite, tubular concretions (fluid conduits), and carbonate-cemented, thin sandstone beds and burrows within otherwise impermeable mudstones. A few seeps were large enough to develop talus-debris piles on their flanks, which were populated by lucinid bivalves and terebratulid brachiopods. Firmgrounds and hardgrounds were common, as evidenced by trace fossil associations or caryophyllid coral thickets atop some seep-carbonate deposits. Thus, the New Zealand examples show strong evidence of formation in sediments at or just beneath the seafloor, but some were clearly exhumed by erosion to sustain later non-seep, epifaunal and boring paleocommunities.

Description: We have conducted a study of hydrothermal plumes overlying the Mid-Atlantic Ridge near 5° S to investigate whether there is a significant export flux of dissolved Fe from hydrothermal venting to the oceans. Our study combined measurements of plume-height Fe concentrations from a series of 6 CTD stations together with studies of dissolved Fe speciation in a subset of those samples. At 2.5 km down plume from the nearest known vent site dissolved Fe concentrations were ∼ 20 nM. This is much higher than would be predicted from a combination of plume dilution and dissolved Fe(II) oxidation rates, but consistent with stabilisation due to the presence of organic Fe complexes and Fe colloids. Using Competitive Ligand Exchange-Cathodic Stripping Voltammetry (CLE-CSV), stabilised dissolved Fe complexes were detected within the dissolved Fe fraction on the edges of one non-buoyant hydrothermal plume with observed ligand concentrations high enough to account for stabilisation of ∼ 4 of the total Fe emitted from the 5° S vent sites. If these results were representative of all hydrothermal systems, submarine venting could provide 12-22 of the global deep-ocean dissolved Fe budget. © 2008 Elsevier B.V. All rights reserved.

Description: This study describes work aimed at the rapid evaluation of the fatty acid (FA) composition of Turkish Rhododendron species, particularly the leaves and the flowers of the toxic plants, R. ponticum and R. luteum. The FA profiles of the available parts of three other nonpoisonous Rhododendron species were also investigated. Subtotal extracts obtained (using n-hexane, chloroform and methanol) from total chloroform:methanol (1:1) extracts were analyzed and compared to each other. Palmitic acid was found to be the most abundant FA in almost all Rhododendron extracts, and the majority of leaf and flower extracts contained significant portions of C18 unsaturated FAs (18:1n-9, 18:2n-6, 18:3n-3). The n-hexane extracts of R. ponticum leaves and R. luteum flowers were unique, as they contained an unusual series of even-chain iso FAs (C16–C24). Especially the n-hexane extracts were found to comprise uncommon FAs with odd-numbered carbons (C13–C29). Overall, n-hexane proved to be the best solvent by representing the richest FA profile, whereas chloroform or methanol appeared less suitable for FA analyses. Appreciable intra-species variations in FA compositions among the leaves as well as other anatomical parts examined were observed. This study highlights the chemotaxonomical importance of the FAs for the genus Rhododendron.

Description: Enoyl-ACP reductase (FabI) is a key enzyme of the type II fatty acid biosynthesis (FAS-II) pathway and a validated antimicrobial target. In the current study, three linear sesquiterpene lactones obtained from Anthemis auriculata, namely anthecotulide (1), 4-hydroxyanthecotulide (2) and 4-acetoxyanthecotulide (3) were evaluated for specific inhibitory effects against the FabI enzyme from three pathogenic microorganisms, Plasmodium falciparum (PfFabI), Mycobacterium tuberculosis (MtFabI) and Escherichia coli (EcFabI). In addition, the compounds were also tested against two elongation enzymes from the plasmodial FAS-II system, β-ketoacyl-ACP reductase (PfFabG) and β-hydroxyacyl-ACP deydratase (PfFabZ). The compounds showed clear differentiation in inhibition of FabI enzymes from different microorganisms. Anthecotulide (1) was most active against MtFabI (IC50 4.5 μg/ml), whereas the oxygenated derivatives thereof (compounds 2 and 3) specifically inhibited plasmodial FAS-II enzymes, PfFabI and PfFabG (IC50 values 20–75 μg/ml). All compounds were inactive towards EcFabI. In whole cell assays, all three compounds exhibited antimalarial and antibacterial activities.

Description: Total syntheses of the title natural products, pseudopyronines A (1) and B (2), have been achieved using methyl β-oxo carboxylic ester starting materials. The natural products and a small set of structurally related compounds were evaluated for growth inhibitory activity against a range of pathogenic microorganisms and were found to exhibit good potency (IC50≥0.46 μg/mL) and selectivity towards Leishmania donovani. Several of the compounds inhibited recombinant fatty acid biosynthesis enzymes from both Plasmodium falciparum and Mycobacterium tuberculosis, validating these targets in the search for new anti-infective agents.

Description: Resin glycosides are secondary metabolites exclusive to the convolvulaceous plants. In this study, crypthophilic acids A–C (1–3), the first resin glycosides occurring in another family (Scrophulariaceae), and the other constituents of Scrophularia cryptophila were examined for in vitro antiprotozoal and antimycobacterial potentials. Except for crypthophilic acid B (2), all tested compounds exhibited growth-inhibitory effect against Trypanosoma brucei rhodesiense, with l-tryptophan (6) and buddlejasaponin III (7) being the most potent ones (IC50's 4.1 and 9.7 μg/ml). In contrast, the activity towards Trypanosoma cruzi was poor, and only crypthophilic acid C (3), 6 and 7 were trypanocidal at concentrations above 40 μg/ml. With the exception of 2 and 6, all compounds were active against Leishmania donovani. Harpagide (4) and 3 emerged as the best leishmanicidal agents (IC50's 2.0 and 5.8 μg/ml). Only compounds 3, 6 and 7 showed antimalarial activity against Plasmodium falciparum with IC50 values of 4.2, 16.6 and 22.4 μg/ml. Overall the best and broadest spectrum activity was presented by compounds 3 and 7, as they inhibited all four parasitic protozoa. None of the isolates had significant activity against Mycobacterium tuberculosis (MICs 〉100 μg/ml) or were toxic towards mammalian (L6) cells. This is the first report of antiprotozoal activity for natural resin glycosides, as well as for harpagide (4), acetylharpagide (5), tryptophan (6) and buddlejasaponin III (7).

Description: The Kuroko deposits of NE Honshu are a key type deposit for the study of volcanogenic massive sulfide deposits. However, these deposits have not been studied in detail since the early 1980's and knowledge of their mode of formation is now dated. In this study, we present the analysis of 12 samples of the Kuroko deposits, 12 samples of submarine hydrothermal minerals from the Sunrise deposit and 6 samples from Suiyo Seamount, both of which are located on the Izu-Ogasawara (Bonin) Arc, for 27 elements. For the Kuroko deposit, Cd〉Sb〉Ag〉Pb〉Hg〉As〉Zn〉Cu are highly enriched, Au〉Te〉Bi〉Ba〉Mo are moderately enriched, In〉Tl are somewhat enriched and Fe is not significantly enriched relative to the average continental crust. Within each of these deposits, a similar pattern of element associations is apparent: Zn–Pb with As, Sb, Cd, Ag, Hg, Tl and Au; Fe–Cu–Ba with As, Sb, Ag, Tl, Mo, Te and Au; Si–Ba with Ag and Au; CaSO4. The enrichment of the chalcophilic elements in these deposits is consistent with hydrothermal leaching of these elements from the host rocks which are dominantly rhyolite–dacite in the case of the Kuroko deposits, rhyolite in the case of the Sunrise deposit and dacite–rhyolite in the case of the Suiyo Seamount deposit. However, this pattern of element enrichment is also similar to that observed in fumarolic gas condensates from andesitic volcanoes. This suggests that there may be a significant magmatic contribution to the composition of the hydrothermal fluids responsible for the formation of the Kuroko deposits, although it is not yet possible to quantify the relative contributions of these two sources of elements. The compositional data show that Sunrise and Suiyo Seamount deposits are much closer compositionally to the Kuroko deposits from NE Honshu than are the submarine hydrothermal deposits from the JADE site in the Okinawa Trough which contain, on average, significantly higher concentrations of Pb, Zn, Sb, As and Ag than each of these deposits. In spite of the greater similarity in tectonic setting of the Hokuroku Basin in which the Kuroko deposits formed to the Okinawa Trough (intracontinental rifted back-arc basin) compared to Myojin Knoll and Suiyo Seamount (active arc volcanoes), it appears that submarine hydrothermal deposits from Myojin Knoll and Suiyo Seamount are closer analogues of the Kuroko deposit than are those from the Okinawa Trough. The present data are consistent with the magmatic hydrothermal model for the formation of Kuroko-type deposits as formulated by Urabe and Marumo [Urabe, T., Marumo, K., 1991. A new model for Kuroko-type deposits of Japan. Episodes 14, 246–251].

Description: The goal of this study was to test whether it is possible to produce early hatching cysts of Artemia franciscana from San Francisco Bay (SFB) by truncation selection. The starting material was an SFB cyst sample, harvested in nature. After selection of early hatching nauplii had taken place, these selected individuals were cultured to maturity, and the hatching rate of their offspring (F1) was compared with that of the parental generation and with the non-selected control F1. The possible differences in hatching rate were used to estimate heritability. Two different selection experiments were run, accompanied with a number of additional tests studying the influence of the hatching set-up, the hatching temperature and diapause termination using hydrogen peroxide, on the hatching rate. Also the influence of different culture salinities on hatching rate and on possible success of selection was studied. The results revealed an influence of all those abiotic factors on the hatching rate, but also a marked interference of the hatching percentage with the hatching rate. Choosing the individuals based on their own phenotypic values (hatching within a certain time span of hatching incubation) and using those to produce the next generation, revealed a positive response. The selection in different salinities showed a different response. Depending on the strength of the selection pressure, the samples were advanced in time, starting with the highest selection pressure, and ending with the control and the parental sample. In spite of the strong interference of environmental factors, our results suggest that selection of early hatching cysts is possible.

Description: Over much of the world's surface oceans, nitrate and phosphate concentrations are below the limit of detection (LOD) of conventional techniques of analysis. However, these nutrients play a controlling role in primary productivity and carbon sequestration in these waters. In recent years, techniques have been developed to address this challenge, and methods are now available for the shipboard analysis of nanomolar (nM) nitrate and phosphate concentrations with a high sample throughput. This article provides an overview of the methods for nM nitrate and phosphate analysis in seawater. We outline in detail a system comprising liquid waveguide capillary cells connected to a conventional segmented-flow autoanalyser and using miniaturised spectrophotometers. This approach is suitable for routine field measurements of nitrate and phosphate and achieves LODs of 0.8 nM phosphate and 1.5 nM nitrate. © 2008 Elsevier Ltd. All rights reserved.

Description: Literature data from 1905/06, 1912/13 and 1949/50 were compared with recent data (2001-2003) from Kiel Bight in order to investigate changes in phytoplankton composition and biomass, which may serve as indicators of environmental changes. In terms of biomass, diatomophyceae and dinophyceae are by far the most important groups. Their ratio is still close to unity. The share of diatomophyceae increased strongly in years with exceptionally high summer blooms (2001) or exceptionally early spring blooms (2003). The summer and autumn blooms of Chaetoceros and Skeletonema, detected in the early 20th century, are replaced by other diatoms (Cerataulina pelagica, Dactyliosolen fragilissimus, Proboscia alata, Pseudo-nitzschia spp.). Chaetoceros and Skeletonema are still important components of the spring blooms. Now as before, the autumn blooms are dominated by Ceratium spp., sometimes also by diatoms. Newly appearing bloom-forming species are mostly potentially toxic (Dicryocha speculum, Prorocentrum minimum, Pseudo-nitzschia spp.). The total phytoplankton biomass has roughly doubled in the course of the last century. The reference condition for phytoplankton biomass in Kiel Bight in the sense of the Water Framework Directive was defined at 55 mg C m(-3) (+/- 10%, annual mean). The mean annual biomass of diatomophyceae and dinophyceae was 25 mg C m-3 (+/- 40%) for each, indicating that the sum of their carbon biomass amounted to 90% (+/- 10%) of the total phytoplankton biomass on an annual average. Diatomophyceae represented at least 80% of carbon biomass in the spring bloom peak at the beginning of the 20th century

Description: Nitrogen loadings to coastal waters have increased over the last century, resulting in deterioration in water quality. In this study we investigated the distributions and seasonality of dissolved organic nitrogen (DON), and its relationship to total dissolved nitrogen (TDN), for two anthropogenically influenced estuarine systems in southwest England. Concentrations of DON in both estuaries were generally 〈 80 μM. DON showed non-conservative distributions, resulting from external and internal inputs and in situ reactivity. DON contributed 38 ± 22 (range 4-79, Yealm) and 36 ± 17 (range 4-84, Plym) to the TDN pool, with lower values generally observed in the fresher samples relative to the more saline samples. DON was a larger fraction of the TDN pool during the summer and autumn relative to winter and spring, indicating the influence of bacterioplankton release on nitrogen cycling in the estuaries. Ammonification and nitrification were observed in the estuaries, processes which were reproduced in incubation experiments using bioreactors. The bioreactor experiments showed that 12 h- 1 of the DON flux from the River Plym may be available to bacteria, indicating significant removal of DON during the residence time of the water in the estuary (a few days). The bioavailable nature of the DON means that this N fraction significantly adds to the eutrophication burden of the receiving coastal waters, and therefore cannot be ignored in environmental assessments. © 2008 Elsevier B.V. All rights reserved.

Description: Concentrations of dissolved iron (DFe) and Fe-binding ligands were determined in the tropical Northeast Atlantic Ocean (12-30°N, 21-29°W) as part of the UK-SOLAS (Surface Ocean Lower Atmosphere Study) cruise Poseidon 332 (P332) in January-February 2006. The surface water DFe concentrations varied between 0.1 and 0.4 nM with an average of 0.22 ± 0.05 nM (n = 159). The surface water concentrations of total Fe-binding ligands varied between 0.82 and 1.46 nM with an average of 1.11 ± 0.14 nM (n = 33). The concentration of uncomplexed Fe-binding ligands varied between 0.64 and 1.35 nM with an average of 0.90 ± 0.14 nM (n = 33). Thus, on average 81 of the total Fe-binding ligand concentration was uncomplexed. The average logarithmic conditional stability constant of the pool of Fe-binding ligands was 22.85 ± 0.38 with respect to Fe 3+ (n = 33). A transect (12°N, 26°W to 16°N, 25.3°W) was sailed during a small Saharan dust event and repeated a week later. Following the dust event, the concentration of DFe increased from 0.20 ± 0.026 nM (n = 125) to 0.25 ± 0.028 (n = 17) and the concentration of free Fe-binding ligands decreased from 1.15 ± 0.15 (n = 4) to 0.89 ± 0.10 (n = 4) nM. Furthermore, the logarithmic stability constants of the Fe-binding ligands south of the Cape Verde islands were distinctively lower than north of the islands. The absence of a change in the logarithmic stability constant after the dust event south of the Cape Verde islands suggests that there was no significant atmospheric input of new Fe-binding ligands during this dust event.

Description: Here we describe the first demonstration of a microbial fuel cell (MFC) as a practical alternative to batteries for a low-power consuming application. The specific application reported is a meteorological buoy (ca. 18-mW average consumption) that measures air temperature, pressure, relative humidity, and water temperature, and that is configured for real-time line-of-sight RF telemetry of data. The specific type of MFC utilized in this demonstration is the benthic microbial fuel cell (BMFC). The BMFC operates on the bottom of marine environments, where it oxidizes organic matter residing in oxygen depleted sediment with oxygen in overlying water. It is maintenance free, does not deplete (i.e., will run indefinitely), and is sufficiently powerful to operate a wide range of low-power marine-deployed scientific instruments normally powered by batteries. Two prototype BMFCs used to power the buoy are described. The first was deployed in the Potomac River in Washington, DC, USA. It had a mass of 230 kg, a volume of 1.3 m3, and sustained 24 mW (energy equivalent of ca. 16 alkaline D-cells per year at 25 °C). Although not practical due to high cost and extensive in-water manipulation required to deploy, it established the precedence that a fully functional scientific instrument could derive all of its power from a BMFC. It also provided valuable lessons for developing a second, more practical BMFC that was subsequently used to power the buoy in a salt marsh near Tuckerton, NJ, USA. The second version BMFC has a mass of 16 kg, a volume of 0.03 m3, sustains ca. 36 mW (energy equivalent of ca. 26 alkaline D-cells per year at 25 °C), and can be deployed by a single person from a small craft with minimum or no in-water manipulation. This BMFC is being further developed to reduce cost and enable greater power output by electrically connecting multiple units in parallel. Use of this BMFC powering the meteorological buoy highlights the potential impact of BMFCs to enable long term (persistent) operation of durable low-power marine instruments (up to 100 mW average power consumption) far longer than practical by batteries.

Description: Large uncertainties remain in the current and future contribution to sea level rise from Antarctica. Climate warming may increase snowfall in the continent’s interior1,2,3, but enhance glacier discharge at the coast where warmer air and ocean temperatures erode the buttressing ice shelves4,5,6,7,8,9,10,11. Here, we use satellite interferometric synthetic-aperture radar observations from 1992 to 2006 covering 85% of Antarctica’s coastline to estimate the total mass flux into the ocean. We compare the mass fluxes from large drainage basin units with interior snow accumulation calculated from a regional atmospheric climate model for 1980 to 2004. In East Antarctica, small glacier losses in Wilkes Land and glacier gains at the mouths of the Filchner and Ross ice shelves combine to a near-zero loss of 4±61 Gt yr−1. In West Antarctica, widespread losses along the Bellingshausen and Amundsen seas increased the ice sheet loss by 59% in 10 years to reach 132±60 Gt yr−1 in 2006. In the Peninsula, losses increased by 140% to reach 60±46 Gt yr−1 in 2006. Losses are concentrated along narrow channels occupied by outlet glaciers and are caused by ongoing and past glacier acceleration. Changes in glacier flow therefore have a significant, if not dominant impact on ice sheet mass balance.

Description: Håkon Mosby mud volcano is located on the SW Barents Sea slope at a water depth of approximately 1250 m. In-situ temperature measurements using gravity corers equipped with autonomous temperature loggers and a short temperature lance operated by an ROV were collected during three cruises between 2003 and 2006, revealing an exceptionally high level of activity and a complex thermal structure of the mud volcano. Simple analytical models were applied to the measured data to estimate rates of specific discharge and to test the hypothesis of episodic mud eruptions. Strongly curved profiles from 4 to 16 m below the seafloor suggest fluid flow at rates from 1 m/year close to the limits of the central area to more than 4 m/year approaching the geometrical center. At the limits of the central area, the profiles show distinct maxima at sediment depths of about 10 to 15 m, which are interpreted as the result of lateral flow. Repeated measurements at shallow depths along a transect crossing the central area revealed a persistent pattern of temperature gradients, while changes in the absolute values point to temporal variability. Temperatures gradients of more than 40 °C/m within the upper half meter of the sediments close to the geometrical center suggest even higher rates of specific discharge than estimated from the deeper profiles. These high rates of fluid flow are most likely accompanied by frequent mud eruptions of small volume and limited local extent.

Description: Numerical simulations of column collapse and pyroclastic density current (PDC) scenarios at Vesuvius were carried out using a transient 3D flow model based on multiphase transport laws. The model describes the dynamics of the collapse as well as the effects of the 3D topography of the volcano on PDC propagation. Source conditions refer to a medium-scale sub-Plinian event and consider a pressure-balanced jet. Simulation results provide new insights into the complex dynamics of these phenomena. In particular: 1) column collapse can be characterized by different regimes, from incipient collapse to partial or nearly total collapse, thus confirming the possibility of a transitional field of behaviour of the column characterized by the contemporaneous and/or intermittent occurrence of ash fallout and PDCs; 2) the collapse regime can be characterized by its fraction of eruptive mass reaching the ground and generating PDCs; 3) within the range of the investigated source conditions, the propagation and hazard potential of PDCs appear to be directly correlated with the flow-rate of the mass collapsing to the ground, rather than to the collapse height of the column (this finding is in contrast with predictions based on the energy-line concept, which simply correlates the PDC runout and kinetic energy with the collapse height of the column); 4) first-order values of hazard variables associated with PDCs (i.e., dynamic pressure, temperature, airborne ash concentration) can be derived from simulation results, thereby providing initial estimates for the quantification of damage scenarios; 5) for scenarios assuming a location of the central vent coinciding with that of the present Gran Cono, Mount Somma significantly influences the propagation of PDCs, largely reducing their propagation in the northern sector, and diverting mass toward the west and southeast, accentuating runouts and hazard variables for these sectors; 6) the 2D modelling approximation can force an artificial radial propagation of the PDCs since it ignores azimuthal flows produced by real topographies that therefore need to be simulated in fully 3D conditions.

Description: Human obesity is a main cause of morbidity and mortality. Recently, several studies have demonstrated an association between the FTO gene locus and early onset and severe obesity. To date, the FTO gene has only been discovered in vertebrates. We identified FTO homologs in the complete genome sequences of various evolutionary diverse marine eukaryotic algae, ranging from unicellular photosynthetic picoplankton to a multicellular seaweed. However, FTO homologs appear to be absent from all other completely sequenced genomes of plants, fungi, and invertebrate animals. Although the biological roles of these marine algal FTO homologs are still unknown, these genes will be useful for exploring basic protein features and could hence help unravel the function of the FTO gene in vertebrates and its inferred link with obesity in humans. © 2007 Springer Science+Business Media, LLC.

Description: A comprehensive database of high precision (± 5 Ma) radiometric ages has been assembled for kimberlites and other alkaline volcanic pipes erupted in southern Africa during the period immediately preceding and following the disruption of Gondwana. These ages show that alkaline volcanic activity in southern Africa has been episodic since Gondwana break-up, and was broadly coeval with episodes of alkaline volcanism elsewhere in Africa. In southern Africa, offshore sedimentation patterns were also episodic, with periods of essentially continuous sedimentation broken by series of major unconformities, linked to plate spreading regimes. The volcanic episodes followed major changes in plate spreading histories and the associated unconformities in the offshore sedimentary record with a lag of 5–13 Ma. On a regional scale, there is an overall younging of volcanic activity from the interior to the margins of southern Africa. Some of the volcanic pipe clusters define a major igneous lineament, with a general age progression younging to the southwest. Parts of this alkaline lineament coincide with major rift zones, but the volcanism predated the surface expression of rifting by as much as 90 Ma. These relationships point to tectonic triggers for alkaline volcanic activity, rather than plumes initiated near the core–mantle boundary. There is also a systematic geographic variation in alkaline magma type across southern Africa, with Mg-rich, less evolved kimberlites emplaced into the Archean craton of the central portions of the sub-continent, and more evolved compositions emplaced into the marginal younger fold belts. These chemical trends are interpreted in terms of decreasing depth of intersection between the CO2–H2O peridotite solidus and the geotherm with increasing geothermal gradient from the Archean craton to the younger marginal fold belts.

Description: Statoliths of cephalopods are small, hard calcareous stones which lie within the cartilaginous skulls of octopods, sepioids and teuthoids1. Fossil statoliths, clearly belonging to genera which are alive today, have previously been described from 11 Cenozoic deposits spanning from the Eocene to the Pleistocene in North America2–5. Such statoliths are of particular interest because they provide a means of studying the evolution of living cephalopod groups which have no calcareous shells, including the cosmopolitan and numerous teuthoids and octopods. Here, the first cephalopod statoliths to be recognized in European deposits are described and identified as Loligo sp. They are compared with the North American fossil Loligo species and statoliths removed from the two living Loligo species of Europe.

Description: The Blato aquifer is situated on the western side of the island of Korčula, southern Dalmatia, Croatia. The terrain is built of karstified carbonate rocks, mostly of the Cretaceous age. In the Blatsko karst polje there are four water supply wells with a total yield of about 60 l/s. The catchment area is 28 km2. The whole terrain is tectonically disturbed and compressed; the most permeable fracture system is perpendicular to the structural “b” axes, which gives rise to a general groundwater direction towards the island’s northern coast. Average precipitation is 850 mm/year, but when there is less than 700 mm/year there is a high possibility of sea-water intrusion during the summer season. The risk significantly increases when dry years repeat. Hydrochemical research has shown that two main pollution sources occur at different hydrological moments: sea-water intrusion happens in the dry summer period when there is maximal extraction and almost no recharge; and the washing of nitrates and other humanly caused pollution indicators from the soil and epikarst belt during the rainy season. All factors must be taken into account when planning management and protection of such a sensitive environment.

Description: The major tectonic elements of the Azores triple junction have been mapped using long-range side-scan sonar. The data enable the Mid-Atlantic Ridge axis to be located with a precision of a few kilometres. Major faults and other tectonic and volcanic elements of the ridge maintain their regional trend of 010° to 020° past the triple junction area. There is no oblique spreading, and only minor transform offsets of the Mid-Atlantic Ridge occur here. The main effect of the triple junction or Azores hot spot is to diminish the amplitude of the median valley to 200 m or less. There is no axial high: a topographic high seen on several profiles is located to the east of the Mid-Atlantic Ridge spreading axis and does not appear to have any fundamental significance. The third arm of the triple junction includes the Azores srreading centre which appears to have developed as a series of en echelon rifted basins (the Terceira Rift) extending from Formigas Trough at 36.8°N, 24.5°W to a point near 39.3°N, 28.8°W. There are indications that recent activity in the spreading centre may be concentrated in a series of ridges which flank the older rifted basins. Until recently the northwest end of the Terceira Rift was connected to the Mid-Atlantic Ridge axis either directly at an RRR junction, or via a transform fault. The triple junction has probably moved south during the last 6 Ma to a positin on the Mid-Atlantic Ridge near 38.7°N. Initiation of the Azores spreading centre may have occurred during the 36 Ma B.P. rearrangement of poles, with an RFF triple junction north from the East Azores fracture zone to the North Azores fracture zone and transferring a wedge of European plate to the African plate. The tectonic elements revealed by this study are in good agreement with inferred earthquake mechanisms and with the RM2 plate tectonic model of Minster and Jordan, but east-west motion between North America and Africa does not seem to be compatible with the other motions at the triple junction unless it is of very recent (2〉3 Ma) origin.

Description: The Zambezi deep-sea fan, the largest of its kind along the east African continental margin, is poorly studied to date, despite its potential to record marine and terrestrial climate signals in the southwest Indian Ocean. Therefore, gravity core GeoB 9309-1, retrieved from 1219 m water depth, was investigated for various geophysical (magnetic susceptibility, porosity, colour reflectance) and geochemical (pore water and sediment geochemistry, Fe and P speciation) properties. Onboard and onshore data documented a sulphate/methane transition (SMT) zone at ~ 450–530 cm sediment depth, where the simultaneous consumption of pore water sulphate and methane liberates hydrogen sulphide and bi-carbonate into the pore space. This leads to characteristic changes in the sediment and pore water chemistry, as the reduction of primary Fe (oxyhydr)oxides, the precipitation of Fe sulphides, and the mobilization of Fe (oxyhydr)oxide-bound P. These chemical processes also lead to a marked decrease in magnetic susceptibility. Below the SMT, we find a reduction of porosity, possibly due to pore space cementation by authigenic minerals. Formation of the observed geochemical, magnetic and mineralogical patterns requires a fixation of the SMT at this distinct sediment depth for a considerable time—which we calculated to be ~ 10 000 years assuming steady-state conditions—following a period of rapid upward migration towards this interval. We postulate that the worldwide sea-level rise at the last glacial/interglacial transition (~ 10 000 years B.P.) most probably caused the fixation of the SMT at its present position, through drastically reduced sediment delivery to the deep-sea fan. In addition, we report an internal redistribution of P occurring around the SMT, closely linked to the (de)coupling of sedimentary Fe and P, and leaving a characteristic pattern in the solid P record. By phosphate re-adsorption onto Fe (oxyhydr)oxides above, and formation of authigenic P minerals (e.g. vivianite) below the SMT, deep-sea fan deposits may potentially act as long-term sinks for P.

Description: The diet of jumbo squid (Dosidicus gigas) off southern-central Chile is described to examine potential biases in the determination of their main prey. Specimens were collected from catches using different fishing gear (jigging, trawl and purse-seine), from July 2003 to January 2004, and from December 2005 to October 2006. The stomach contents were analyzed in terms of frequency of occurrence, number, and weight of prey items and the diet composition was analyzed using Detrended Correspondence Analysis. In the industrial purse-seine fleet for jack mackerel (Trachurus murphyi), the dominant prey of D. gigas was T. murphyi. In the industrial mid-trawl fishery for Patagonian grenadier (Macruronus magellanicus), the dominant species in the diet of D. gigas was M. magellanicus. Similarly, Chilean hake (Merluccius gayi) was the main prey in the diet of D. gigas obtained in the industrial trawl fishery for Chilean hake; and, in both artisanal fisheries (purse-seine for small pelagics and jigging), small pelagic fish and D. gigas were the main prey in the stomach contents of D. gigas. Cannibalism in D. gigas varied between different fleets and probably is related to stress behavior during fishing. The Detrended Correspondence Analysis ordination showed that the main prey in the diet of D. gigas is associated with the target species of the respective fishery. Consequently, biases are associated with fishing gear, leading to an overestimate in the occurrence of the target species in the diet. We recommend analyzing samples from jigging taken at the same time and place where the trawl and purse-seine fleets are operating to avoid this problem, and the application of new tools like stable isotope, heavy metal, and fatty acid signature analyses.

Description: Southern Italy is dominated by extensional tectonics that in the Calabrian arc and Eastern Sicily produced the development of the Siculo–Calabrian Rift Zone (SCRZ). This zone is represented by a ≈ 370 km-long fault belt consisting of 10 to 50 km long distinct fault segments which extend both offshore and on land being also responsible of the crustal seismicity of this region. The geological and morphological observations indicate that the active normal faults of the SCRZ are characterized by throw-rates ranging from 0.7 to 3.1 mm/a. They accommodate an almost uniform horizontal extension-rate of about 3.0 mm/a along a WNW–ESE regional extension direction. Based on our field observations and following empirical relationships between magnitude and surface rupture length connections between large crustal earthquakes and distinct fault segments of the SCRZ have been also tentatively tested. Our data indicate moreover that the magnitudes (M) of the historical and instrumental earthquakes are consistent with the estimated values and that the geometry and kinematics of the fault segments and the related different crustal features of the SCRZ control the different seismic behaviours of adjacent portions of the active rift zone.

Description: Dissolved organic carbon (DOC) in the oceans is one of the largest dynamic reservoirs of carbon on earth, comparable in size to the atmospheric reservoir of carbon (as CO2) in the atmosphere, or to the amount of carbon in all terrestrial and aquatic biota. The concerted efforts of earth scientists, atmospheric scientists, and biologists who study global biogeochemical cycles and the earth's climate have yielded a rather detailed understanding of carbon in the atmosphere and in biota. Marine dissolved organic matter (DOM) is far less well characterized, principally because it exists as a highly diluted mixture of perhaps millions of organic compounds in a highly saline aqueous solution. Prior to 2007, only around 1/3 of marine DOM was typically recovered from seawater for research purposes, regardless of the method of isolation. In 2007, reverse osmosis (RO) and electrodialysis (ED) were coupled to achieve recoveries of 64–93% of marine DOM. The level of residual salts in the concentrated samples, however, still precluded the characterization of marine DOM by solid-state NMR, mass spectrometry, or even elemental analysis. This paper describes a major improvement to the RO/ED method, in which pulsed ED is used (at sea) to reach roughly 100-fold greater removal of salts compared to non-pulsed ED while maintaining comparable recoveries of DOM.

Description: Changes in population structure of the jumbo flying squid Dosidicus gigas in Peruvian waters were studied based on size-at-maturity from 1989 to 2004. From 1989 to 1999, mature squid belonging to the medium-sized group prevailed, but from 2001 on, mature squids were larger. This change is not related to the changes in sea surface temperature and we hypothesized that it was caused by the population increase of mesopelagic fishes as prey.

Description: The reproductive biology of two species of endemic Southern Ocean octopods was investigated around the sub-Antarctic islands of South Georgia and Shag Rocks. The females of both the species produce few, large eggs. This appears to be governed by phylogenetic constraint. No evidence was found for ontogenetic migration or seasonality associated with gonad maturation. Based on oocyte length frequency distributions and observations of oocyte development within the ovary, it is possible that both species could have either a single or multiple-batch spawning strategy. Pareledone turqueti ovaries contained fewer larger oocytes than those of Adelieledone polymorpha, which may help to reduce competition for resources immediately after hatching.

Description: The role of tephrochronology, as a dating and stratigraphic tool, in precise palaeoclimate and environmental reconstruction, has expanded significantly in recent years. The power of tephrochronology rests on the fact that a tephra layer can stratigraphically link records at the resolution of as little as a few years, and that the most precise age for a particular tephra can be imported into any site where it is found. In order to maximise the potential of tephras for this purpose it is necessary to have the most precise and robustly tested age estimate possible available for key tephras. Given the varying number and quality of dates associated with different tephras it is important to be able to build age models to test competing tephra dates. Recent advances in Bayesian age modelling of dates in sequence have radically extended our ability to build such stratigraphic age models. As an example of the potential here we use Bayesian methods, now widely applied, to examine the dating of some key Late Quaternary tephras from Italy. These are: the Agnano Monte Spina Tephra (AMST), the Neapolitan Yellow Tuff (NYT) and the Agnano Pomici Principali (APP), and all of them have multiple estimates of their true age. Further, we use the Bayesian approaches to generate a revised mixed radiocarbon/varve chronology for the important Lateglacial section of the Lago Grande Monticchio record, as a further illustration of what can be achieved by a Bayesian approach. With all three tephras we were able to produce viable model ages for the tephra, validate the proposed 40Ar/39Ar age ranges for these tephras, and provide relatively high precision age models. The results of the Bayesian integration of dating and stratigraphic information, suggest that the current best 95% confidence calendar age estimates for the AMST are 4690–4300 cal BP, the NYT 14320–13900 cal BP, and the APP 12380–12140 cal BP.

Description: From 1998 to 2001 a total of 200 Ommastrephes bartramii (27 paralarvae) and 170 Sthenoteuthis oualaniensis (14 paralarvae) were sampled from the Central North Pacific. One group of non-paralarval O. bartramii (n = 30) was sampled from farther northwest in 1996. The δ15N of mantle muscle of non-paralarval O. bartramii ( x¯¯¯ = 12.4‰) was significantly greater than that of non-parlarval S. oualaniensis (x¯¯¯ = 8.1‰) (P 〈 0.001). The δ15N of whole paralarvae of O. bartramii (x¯¯¯ = 6.4‰) was not significantly different than parlarvalae of S. oualaniensis (x¯¯¯ = 6.1‰) (P = 0.528). There was no significant difference between the mantle muscle δ15N values of male (n = 95, x¯¯¯ = 13.3‰) and female (n = 18, x¯¯¯ = 12.9 ‰) O. bartramii greater than 300 mm mantle length (ML) (P = 0.15). There was also no significant difference between the mantle muscle δ15N values of male (n = 15, x¯¯¯ = 7.2‰) and female (n = 26, x¯¯¯ = 7.3 ‰) S. oualaniensis in the same size range (P = 0.41). Overall there was a distinct logistic increase in δ15N with mantle length for O. bartramii, whereas S. oualaniensis showed an exponential increase in δ15N with mantle length that was stronger within individual years than with all samples combined. In general, adult O. bartramii are more than a trophic level above S. oualaniensis (4.3‰, 1.3 TLs). Because of the nature of the sampling protocol, this study could not separate spatial and temporal effects on the δ15N signals from each squid species. This study demonstrates the ability of stable isotope analyses to differentiate trophic levels between squid species as well as track trophic changes across size ranges from paralarvae to adults. Additional research is needed to validate these trophic changes across size within individuals.

Description: A detailed field mapping, coupled with structural analyses and morphological investigation, has been carried out along the northern and western borders of the Hyblean Plateau (SE Sicily), in order to define the nature and the kinematics of a major Quaternary fault belt. This, here designed as the Scicli Line Fault Belt, is composed of two N50 oriented extensional basins that, linked by a regional N10 trending transfer zone, originated during the Early Pleistocene and experienced, since the Late Quaternary, a positive tectonic inversion. In both the two stages of deformation, the Scicli Line Fault Belt has been characterised by displacement-rate comparable with the relative velocities measured between the distinct plates composing the central Mediterranean region. In the period going from 1.5–1.2 to 0.85 Ma, the fault belt accommodated the entire divergence between Adria and Nubia. At present, the Scicli Line Fault Belt absorbs most of the Nubia–Eurasia convergence, while the western divergent margin of the Adria microplate has jumped to the eastern and the southern margins of the Hyblean Plateau, along the Late Quaternary Siculo–Calabrian Rift Zone. The off-shore prolongation of the two tectonic boundaries of the Hyblean Plateau has been recognised in the Sicily Channel, where they are both interrupted by a WNW-ESE oriented dextral fault. According to our reconstruction, the Hyblean Plateau represents an isolated lithospheric block, whose evolution can be related to the propagation of the western divergent margin of the Adria microplate, accompanied with the southward migration of the triple junction between Eurasia, Nubia and Adria. In this new large-scale kinematic picture, the GPS velocity measured in the Hyblean region, at the permanent site of NOTO, is actually representative of the local kinematics, rather than of the entire African promontory of southern Italy. This implies a correction of previous regional kinematic models based on combination of GPS vectors. In particular, our data constrain a new interpretation both for the kinematics along the E–W oriented Nubia–Eurasia margin, dominated by prevalent dextral deformation rather than reverse motions, and for the intraplate deformation in the Sicily Channel, within the Africa promontory, which would be dominated by a roughly N110° oriented extension. This conclusion has implication also on the mechanism and the origin of the Pantelleria–Linosa–Malta Rift that is here interpreted as a transtensive feature developed along a major transform fault, rather than the result of passive rifting induced by the Nubia–Eurasia collision, as it is currently interpreted.

Description: Correlation of distal ash deposits with their proximal counterparts mainly relies on chemical and mineralogical characterization of bulk rock and matrix glasses. However, the study of juvenile fragments often reveals the heterogeneity in terms of clast shape, external surface, groundmass texture and composition. This is particularly evident in small scale eruptions, characterized by a strong variability in texture and relative abundance of juvenile fragments. This heterogeneity introduces an inherent uncertainty, that makes the compositional data alone inadequate to unequivocally characterize the tephra bed. Pyroclast characteristics, if described and quantified, can represent an additional clue for the correct identification of the tephra. The paper presents morphological, textural and compositional data on the products of an ash eruption from Middle Age activity of Vesuvius, to demonstrate the information that can be extracted from the proposed type of analysis. Juvenile fragments from five ash layers throughout the studied products were randomly hand-picked and fully characterized in terms of external morphology, particle outline parameterization, groundmass texture and glass composition. Statistical analysis of shape parameters characterized groups of fragments that can be compared with the other textural and physical parameters. The main result is that the data do not show important cross-correlation so suggesting that all of these parameters, together with accurate field data are needed for the complete fingerprinting of a tephra bed. We suggest that this approach is especially important for characterizing the products of small scale, compositionally undistinguishable, eruptions and represents the necessary step to deal with before going into more detailed compositional analyses.

Description: Female reproductive features have been investigated in five polar and deep-sea bobtail squid genera Rossia and Neorossia (R. macrosoma, R. moelleri, R. pacifica, N.c. caroli and N.c. jeannae). These species are characterized by asynchronous ovary maturation, very large eggs (〉10% ML), fecundity of several hundred oocytes, very high reproductive output, and continuous spawning with low batch fecundity. This adaptive complex of reproductive traits evolved in these small animals as an optimum strategy for polar and deep-water habitats.

Description: Temperature measurements made in Ocean Drilling Program (ODP) Hole 642E are used to estimate bulk crustal permeability. Hole 642E is located on the Vøring Plateau near the transition between oceanic and continental crust on a volcanically rifted margin. A temperature–depth profile measured 20 yr after the hole was drilled indicates fluid flowing from the basement, up the Hole and into the ocean. This flow regime suggests that the basement is naturally over pressured with respect to hydrostatic. We estimate the up-hole flow rate to be approximately 6–11 m h− 1. This flow rate, coupled with an estimated minimum differential overpressure of 13–20 kPa, and an estimated aquifer thickness of 100 m, yields a bulk permeability of 10− 13 m2. This result suggests that fluid flow through basement may be an important component of passive margin hydrology.

Description: One hundred eighty U–Th data, including 23 isochrons on 24 pristine modern and Holocene corals and 33 seawater samples, were analyzed using sector-field mass spectrometry to understand the variability of initial 230Th/232Th (230Th/232Th0). This dataset allows us to further assess the accuracy and precision of coral 230Th dating method. By applying quality control, including careful sampling and subsampling protocols and the use of contamination-free storage and workbench spaces, the resulting low procedural blanks give an equivalent uncertainty in age of only ±0.2–0.3 yr for 1–2 g of coral sample. Using site-specific 230Th/232Th0 values or isochron techniques, our study demonstrates that corals with an age less than 100 yrs can be 230Th-dated with precisions of ±1 yr. Six living subtidal coral samples were collected from two continental shelf sites, Nanwan off southern Taiwan in the western Pacific and Son Tra off central Vietnam in the South China Sea; one coral core was drilled from an open-ocean site, Santo Island, Vanuatu, in the western tropical Pacific; and modern and fossil intertidal coral slabs, 17 in total, were cut from six sites around the islands of Simeulue, Lago, North Pagai and South Pagai of Sumatra in the eastern Indian Ocean. The results indicate that the main source of thorium is the dissolved phase of seawater, with variation of 230Th/232Th0 depending on local hydrology. With intense input of terrestrial material, low 230Th/232Th0 atomic ratios of 4.9 × 10−6 and 3.2 × 10−6 with a 10% variation are observed in Nanwan and Son Tra, respectively. At the Santo site, we find a value of 5.6 × 10−6 at 4 horizons and one high value of 24 × 10−6 in a sample from AD 1974.6 ± 0.5, likely due to the upwelling of cold water during a La Niña event between AD 1973 and 1976. The natural dynamics of 230Th/232Th0 recorded in the intertidal corals at sites in the Sumatran islands are complicated so that this value varies significantly from 3.0 to 9.4 × 10−6. Three of the 141 modern coral 230Th ages differ from their true ages by −23 to +4, indicating the presence of detrital material with anomalous 230Th/232Th values. Duplicate measurement of coeval subsamples is therefore recommended to verify the age accuracy. This improved high precision coral 230Th dating method raises the prospects of refining the age models for band-counted and tracer-tuned chronologies and of advancing coral paleoclimate research.

Description: Marine sediments from the Vøring Plateau (Norwegian Sea) have been studied for their dinoflagellate cyst (dinocyst) and foraminiferal content in order to reconstruct sea-surface conditions in the eastern Norwegian Sea during Marine Isotope Stage (MIS) 5e. In combination with stable oxygen isotope and ice rafted detritus (IRD) data, the variations in foraminiferal and dinocyst assemblage composition reflect a stepwise transition from the final phase of deglaciation (Termination II) into typical interglacial conditions. This stepwise change is repeated subsequently during the cooling conditions of glacial inception towards MIS 5d. The interval studied is characterized by relatively high abundances of Bitectatodinium tepikiense, in comparison to present-day values in the area, indicating a larger seasonal temperature amplitude with enhanced surface water stratification during MIS 5e. The important occurrence of the warm-temperate dinocyst Spiniferites mirabilis s.l. concurrent with subpolar foraminifers Turborotalita quinqueloba, Globigerina bulloides, and Globigerinita glutinata reveals that most pronounced interglacial marine conditions prevailed in the area just prior to the transition towards MIS 5d. The late stratigraphic position of this phase in the interglacial is verified by comparison with dinocyst data from south of Iceland, manifesting its over-regional implication. Besides the good agreement in dinocyst and foraminiferal assemblage changes, the variations in and between both fossil assemblages also point to the existence of some significant surface water variability in the eastern Norwegian Sea during MIS 5e.

Description: For paleoceanographic studies, it is important to understand the processes that influence the calcium (Ca) isotopic composition of foraminiferal calcite tests preserved in the sediment record. Seven species of planktonic foraminifera from coretop sediments collectively exhibited a Ca temperature dependent fractionation of 0.013‰ per °C. This is in agreement with previously published estimates for most species of planktonic foraminifera as well as biogenic and inorganic calcite and aragonite. Four species of planktonic foraminifera collected from a sediment trap showed a considerable amount of scatter and no consistent temperature dependent fractionation. Analyzed size fractions of coretop samples show no significant relationship with δ44/40Ca. However, preliminary results suggest that the symbiotic and spinose foraminifera Globigerinoides sacculifer might exhibit a relationship between test size and δ44/40Ca. A one-box model in which Ca isotopes are allowed to fractionate by Rayleigh distillation from a biomineralization reservoir (internal pool) was used to constrain the isotopic composition of the original biomineralization Ca reservoir, assuming around 85% of the Ca reservoir is precipitated and the fractionation factor during precipitation is 0.9985 + 0.00002(T °C). To explain the foraminiferal Ca isotope data, this model indicates that the Ca isotopic composition of the biomineralization reservoir is offset from seawater (approximately − 0.8‰).

Description: Our recent paper [McMurtry, G.M., Tappin, D.R., Sedwick, P.N., Wilkinson, I., Fietzke, J. and Sellwood, B., 2007a. Elevated marine deposits in Bermuda record a late Quaternary megatsunami. Sedimentary Geol. 200, 155–165.] critically re-examined elevated marine deposits in Bermuda, and concluded that their geological setting, sedimentary relations, micropetrography and microfaunal assemblages were inconsistent with sustained intertidal deposition. Instead, we hypothesized that these deposits were the result of a large tsunami that impacted the Bermuda island platform during the mid-Pleistocene. Hearty and Olson [Hearty, P.J., and Olson, S.L., in press. Mega-highstand or megatsunami? Discussion of McMurtry et al. “Elevated marine deposits in Bermuda record a late Quaternary megatsunami”: Sedimentary Geology, 200, 155–165, 2007 (Aug. 07). Sedimentary Geol. 200, 155–165.] in their response, attempt to refute our conclusions and claim the deposits to be the result of a +21 m eustatic sea level highstand during marine isotope stage (MIS) 11. In our reply we answer the issues raised by Hearty and Olson [Hearty, P.J., and Olson, S.L., in press. Mega-highstand or megatsunami? Discussion of McMurtry et al. “Elevated marine deposits in Bermuda record a late Quaternary megatsunami”: Sedimentary Geology, 200, 155–165, 2007 (Aug. 07). Sedimentary Geol. 200, 155–165.] and conclude that the Bermuda deposits do not provide unequivocal evidence of a prolonged + 21 m eustatic sea level highstand. Rather, the sediments are more likely the result of a past megatsunami in the North Atlantic basin.

Description: Historically, small invertebrate grazers in marine plant communities have been considered to be a relatively homogeneous group in their impact on ecosystem processes. However, recent studies propose that species composition is an important agent in determining grazer effects. We used four mesocosm experiments to test the biomass-specific and density-dependent effects of common mesograzers in temperate regions (Littorina littorea, Rissoa membranacea, Idotea baltica and Gammarus oceanicus) on epiphyte and eelgrass biomass and productivity. Mesograzer species identity strongly influenced epiphyte accumulation and eelgrass growth, where Rissoa was the most efficient mesograzer (per biomass) and Gammarus had the weakest impact. Density-dependent effects varied considerably among species. Both gastropod species reduced epiphyte accumulation in direct proportion to their density, and Littorina had the strongest negative effect on epiphyte biomass. The impact of Idotea seemed to level off to a threshold value and Gammarus had no density-dependent effect on epiphyte accumulation at all. Rissoa and Idotea increased eelgrass productivity in accordance with their effect on epiphyte accumulation, whereas Littorina showed a less positive effect than could be expected by its strong impact on epiphyte biomass. Gammarus had no significant impact on eelgrass growth. Our results show that the different functional traits of superficially similar mesograzers can have important consequences for ecosystem processes in macrophyte systems.

Description: A steady-state reaction-transport model is applied to sediments retrieved by gravity core from two stations (S10 and S13) in the Skagerrak to determine the main kinetic and thermodynamic controls on anaerobic oxidation of methane (AOM). The model considers an extended biomass-implicit reaction network for organic carbon degradation, which includes extracellular hydrolysis of macromolecular organic matter, fermentation, sulfate reduction, methanogenesis, AOM, acetogenesis and acetotrophy. Catabolic reaction rates are determined using a modified Monod rate expression that explicitly accounts for limitation by the in situ catabolic energy yields. The fraction of total sulfate reduction due to AOM in the sulfate–methane transition zone (SMTZ) at each site is calculated. The model provides an explanation for the methane tailing phenomenon which is observed here and in other marine sediments, whereby methane diffuses up from the SMTZ to the top of the core without being consumed. The tailing is due to bioenergetic limitation of AOM in the sulfate reduction zone, because the methane concentration is too low to engender favorable thermodynamic drive. AOM is also bioenergetically inhibited below the SMTZ at both sites because of high hydrogen concentrations (∼3–6 nM). The model results imply there is no straightforward relationship between pore water concentrations and the minimum catabolic energy needed to support life because of the highly coupled nature of the reaction network. Best model fits are obtained with a minimum energy for AOM of ∼11 kJ mol−1, which is within the range reported in the literature for anaerobic processes.

Description: Zusammenfassung A turbulence closure for the effect of mesoscale eddies in non-eddy-resolving ocean models is proposed. The closure consists of a prognostic equation for the eddy kinetic energy (EKE) that is integrated as an additional model equation, and a diagnostic relation for an eddy length scale (L), which is given by the minimum of Rhines scale and Rossby radius. Combining EKE and L using a standard mixing length assumption gives a diffusivity (K), corresponding to the thickness diffusivity in the [Gent, P.R., McWilliams, J.C. 1990. Isopycnal mixing in ocean circulation models. J. Phys. Oceanogr. 20, 150-155] parameterisation. Assuming downgradient mixing of potential vorticity with identical diffusivity shows how K is related to horizontal and vertical mixing processes in the horizontal momentum equation, and also enables us to parameterise the source of EKE related to eddy momentum fluxes. The mesoscale eddy closure is evaluated using synthetic data from two different eddy-resolving models covering the North Atlantic Ocean and the Southern Ocean, respectively. The diagnosis shows that the mixing length assumption together with the definition of eddy length scales is valid within certain limitations. Furthermore, implementation of the closure in non-eddy-resolving models of the North Atlantic and the Southern Ocean shows consistently that the closure has skill at reproducing the results of the eddy-resolving model versions in terms of EKE and K.

Description: The baroclinic response of a stratified coastal embayment (Lunenburg Bay of Nova Scotia) to the observed wind forcing is examined using two numerical models. A linear baroclinic model based on the normal mode approach shows skill at reproducing the observed isotherm movements and sub-surface currents during a time of strong stratification in the bay. The linear model also shows that the isotherm movement in Lunenburg Bay is influenced by the wind forcing and propagation of baroclinic Kelvin waves from neighbouring Mahone Bay. The effects of nonlinearity and topography are investigated using a three-dimensional nonlinear coastal circulation model. The nonlinear model results demonstrate that the nonlinear advection terms generate a gyre circulation at the entrance of Lunenburg Bay, and the slope bottom topography at the mouth of the bay strengthens the sub-surface time-mean inflow on the southern side of the bay. A comparison of model-calculated currents in different numerical experiments clearly shows that baroclinicity plays a dominant role in the dynamics of wind-driven circulation in Lunenburg Bay.

Description: The mussel Mytilus edulis settlement and distribution was studied on plastic panels with manipulated flow regime (faired, bluff, split and angled) with or without water soluble metabolites of the green alga Cladophora rupestris. The panels were exposed vertically on a device (hydrovane) that ensures their constant orientation in the current during the peak of larval settlement at 1 m depth. In order to investigate larval distribution on the panels, half of them were coated with a silicone vacuum grease that prevents larvae from de-attachment. This grease was not toxic and did not attract or repel larvae. Low densities of larvae on the un-greased plates compared to the greased ones suggested that some of larvae left the substratum. The blue mussel larvae initially settled in regions of reduced shear velocity and then redistribute to the regions of high shear velocity. The presence of the alga increased the density of blue mussel larvae and changed their distribution on the panels. Overall, our results demonstrated that larval recruitment of M. edulis is an active process affected both by boundary-layer hydrodynamics and algal waterborne compounds.