ALBERT

Description: Anaerobic oxidation of methane (AOM) was shown to reduce methane emissions by over 50% in freshwater systems, its main natural contributor to the atmosphere. In these environments iron oxides can become main agents for AOM, but the underlying mechanism for this process has remained enigmatic. By conducting anoxic slurry incubations with lake sediments amended with 13C-labeled methane and naturally abundant iron oxides the process was evidenced by significant 13C-enrichment of the dissolved inorganic carbon pool and most pronounced when poorly reactive iron minerals such as magnetite and hematite were applied. Methane incorporation into biomass was apparent by strong uptake of 13C into fatty acids indicative of methanotrophic bacteria, associated with increasing copy numbers of the functional methane monooxygenase pmoA gene. Archaea were not directly involved in füll methane oxidation, but their crucial participation,likely being mediators in electron transfer, was indicated by specific inhibition of their activity that fully stopped iron-coupled AOM. By contrast, inhibition of sulfur cycling increased 13C-methane turnover, pointing to sulfur species involvement in a competing process. Our findings suggest that the mechanism of iron-coupled AOM is accomplished by a complex microbemineral reaction network, being likely representative of many similar but hidden interactions sustaining life under highly reducing low energy conditions.

Description: Highlights • The Fram Slide Complex has been active from late Miocene to late Pleistocene. • Local processes were critical for slope stability in the Fram Strait area. • Toe erosion caused by normal faulting may have led to retrogressive failure. • Low gradient contourite drifts might smooth and stabilize submarine slopes. • Low tsunami potential from the Fram Slide Complex could increase in the future. Abstract The best known submarine landslides on the glaciated NW European continental margins are those at the front of cross-shelf troughs, where the alternation of rapidly deposited glycogenic and hemi pelagic material generates sedimentary overpressure. Here, we investigate landslides in two areas built of contourite drifts bounded seaward by a ridge-transform junction. Seismic and bathymetric data from the Fram Slide Complex are compared with the tectonically similar Vastness area ~ 120 km to the south, to analyze the influence of local and regional processes on slope stability. These processes include tectonic activity, changes of climate and oceanography, gas hydrates and fluid migration systems, slope gradient, toe erosion and style of contourite deposition. Two areas within the Fram Slide Complex underwent different phases of slope failures, whereas there is no evidence at all for major slope failures in the Vastness area. The comparison cannot reveal the distinct reason for slope failure but demonstrates the strong impact of variation in the local controls on slope stability. The different failure chronologies suggest that toe erosion, which is dependent on the throw of normal faults, and the different thickness and geometry of contourite deposits can result in a critical slope morphology and exert pronounced effects on slope stability. These results highlight the limitations of regional hazard assessments and the need for multi-disciplinary investigations, as small differences in local controlling factors led to substantially different slope failure histories.

Description: We used a new sedimentary record from a small kettle wetland to reconstruct the Late Glacial and Holocene vegetation and fire history of the Krutoberegovo-Ust Kamchatsk region in eastern Kamchatka Peninsula (Russia). Pollen and charcoal data suggest that the Late Glacial landscape was dominated by a relatively fire-prone Larix forest-tundra during the Greenland Interstadial complex (GI 1) and a subarctic steppe during the Younger Dryas (GS1). The onset of the Holocene is marked by the reappearance of trees (mainly Alnus incana) within a fern and shrub dominated landscape. The Holocene Thermal Maximum (HTM) features shifting vegetational communities dominated by Alnus shrubs, diverse forb species, and locally abundant aquatic plants. The HTM is further defined by the first appearance of stone birch forests (Betula ermanii) – Kamchatka's most abundant modern tree species. The Late Holocene is marked by shifts in forest dynamics and forest-graminoid ratio and the appearance of new non-arboreal taxa such as bayberry (Myrica) and meadow rue (Filipendula). Kamchatka is one of Earth's most active volcanic regions. During the Late Glacial and Holocene, Kamchatka's volcanoes spread large quantities of tephra over the study region. Thirty-four tephra falls have been identified at the site. The events represented by most of these tephra falls have not left evidence of major impacts on the vegetation although some of the thicker tephras caused expansion of grasses (Poaceae) and, at least in one case, forest die-out and increased fire activity.

Description: Highlights • Receiver functions from ocean-bottom seismometer stations reveal no significant crustal thickening in the surrounding of the Tristan da Cunha hot spot. • The mantle transition zone to the NW of Tristan da Cunha is thickened and cool. • The mantle transition zone is potentially thinned to the south/southwest of Tristan da Cunha. • A thickness of 60 to 75 km beneath Tristan da Cunha argues for a compositional control on the seismological lithosphere in the South Atlantic. Abstract The most prominent hotspot in the South Atlantic is Tristan da Cunha, which is widely considered to be underlain by a mantle plume. But the existence, location and size of this mantle plume have not been established due to the lack of regional geophysical observations. A passive seismic experiment using ocean bottom seismometers aims to investigate the lithosphere and upper mantle structure beneath the hotspot. Using the Ps receiver function method we calculate a thickness of 5 to 8 km for the oceanic crust at 17 ocean-bottom stations deployed around the islands. Within the errors of the method the thickness of the oceanic crust is very close to the global mean. The Tristan hotspot seems to have contributed little additional magmatic material or heat to the melting zone at the mid-oceanic ridge, which could be detected as thickened oceanic crust. Magmatic activity on the archipelago and surrounding seamounts seems to have only effected the crustal thickness locally. Furthermore, we imaged the mantle transition zone discontinuities by analysing receiver functions at the permanent seismological station TRIS and surrounding OBS stations. Our observations provide evidence for a thickened (cold) mantle transition zone west and northwest of the islands, which excludes the presence of a deep-reaching mantle plume. We have some indications of a thinned, hot mantle transition zone south of Tristan da Cunha inferred from sparse and noisy observations, which might indicate the location of a Tristan mantle plume at mid-mantle depths. Sp receiver functions image the base of lithosphere at about 60 to 75 km beneath the islands, which argues for a compositionally controlled seismological lithosphere-asthenosphere boundary beneath the study area.

Description: Highlights • Observations show that formation of sediment-laden sea ice occurs in coastal polynyas in winter. • Sea ice rafted sediments are a significant component of the Laptev Sea’s sediment budget. • No observational evidence for sediment entrainment into sea ice in mid-shelf polynyas at water depth greater than 20 m. Abstract Sea ice is an important vehicle for sediment transport in the Arctic Ocean. On the Laptev Sea shelf (Siberian Arctic) large volumes of sediment-laden sea ice are formed during freeze-up in autumn, then exported and transported across the Arctic Ocean into Fram Strait where it partly melts. The incorporated sediments are released, settle on the sea floor, and serve as a proxy for ice-transport in the Arctic Ocean on geological time scales. However, the formation process of sediment-laden ice in the source area has been scarcely observed. Sediment-laden ice was sampled during a helicopter-based expedition to the Laptev Sea in March/April 2012. Sedimentological, biogeochemical and biological studies on the ice core as well as in the water column give insights into the formation process and, in combination with oceanographic process studies, on matter fluxes beneath the sea ice. Based on satellite images and ice drift back-trajectories the sediments were likely incorporated into the sea ice during a mid-winter coastal polynya near one of the main outlets of the Lena River, which is supported by the presence of abundant freshwater diatoms typical for the Lena River phytoplankton, and subsequently transported about 80 km northwards onto the shelf. Assuming ice growth of 12 to 19 cm during this period and mean suspended matter content in the newly formed ice of 91.9 mg l-1 suggests that a minimum sediment load of 8.4x104 t might have been incorporated into sea ice. Extrapolating these sediment loads for the entire Lena Delta region suggests that at least 65% of the estimated sediment loads which are incorporated during freeze-up, and up to 10% of the annually exported sediment load may be incorporated during an event such as described in this paper.

Description: The Eastern Baltic cod abundance started rapidly to increase in the mid-2000s as evidenced by analytical stock assessments, due to increased recruitment and declining fishing mortality. Since 2014, the analytical stock assessment is not available, leaving the present stock status unclear and casting doubts about the magnitude of the recent increase in recruitment. Earlier studies identified main factors impacting on cod reproductive success to be related to the loss of two out of three spawning areas in the 1980s caused by lack of major Baltic inflows with a concurrent reduction in salinity and oxygen. Other important factors include prey availability for first-feeding larvae, egg predation by sprat and herring and cannibalism on juveniles, all in one way or the other related to the prevailing hydrographic conditions. These factors cannot explain increased reproductive success in the last decade, as the period was characterized by an absence of large-scale Baltic inflows since 2003 and persistent anoxic conditions in the bottom water of the deep Baltic basins. This questions the perception of the increased recruitment in later years and challenges our present understanding of cod recruitment dynamics in the Baltic Sea. In this contribution, we review evidence from the recent literature supplemented by information from latest research cruises to elucidate whether cod reproductive success indeed has increased during the last decade, and we suggest the key processes responsible for the recent dynamics in cod recruitment and outline directions for future research.

Description: The recent volcanic eruptions of Eyjafjallajökull 2010 and Grímsvötn 2011 demonstrated the risks that mediumsized explosive Icelandic eruptions pose to the North Atlantic region. Using the Eyjafjallajökull 2010 eruption as a case study, we assess how traceable such eruptions are in the marine sedimentary record at medial distances from the source and investigate which factors have affected the particle transport to the marine sedimentary archive. During R/V Poseidon cruise 457, we recovered 13 box cores at 100–1600 m water depths and distances of 18–180 km southwest, south, and east of Iceland. Volcanic glass shards from the uppermost surface sediment were analyzed for their major element composition by electron microprobe and assigned to their eruptive source by geochemical fingerprinting. The predominantly basaltic particles are mostly derived from the Katla, Grímsvötn-Lakagígar, and Bárðarbunga-Veiðivötn volcanic systems. We also identified rhyolitic particles from the Askja 1875 and Öræfajökull 1362 eruptions. Only three out of almost 900 analyzed glass shards are derived from the recent Eyjafjallajökull 2010 eruption, suggesting that medium-sized eruptions are only poorly preserved in marine sediments located at medial distances southwest to east of Iceland. We conclude that the frequency of past medium-sized eruptions is likely higher than detectable in this archive.

Description: Environmental histories that span the last full glacial cycle and are representative of regional change in Australia are scarce, hampering assessment of environmental change preceding and concurrent with human dispersal on the continent ca. 47,000 years ago. Here we present a continuous 150,000-year record offshore south-western Australia and identify the timing of two critical late Pleistocene events: wide-scale ecosystem change and regional megafaunal population collapse. We establish that substantial changes in vegetation and fire regime occurred B70,000 years ago under a climate much drier than today. We record high levels of the dung fungus Sporormiella, a proxy for herbivore biomass, from 150,000 to 45,000 years ago, then a marked decline indicating megafaunal population collapse, from 45,000 to 43,100 years ago, placing the extinctions within 4,000 years of human dispersal across Australia. These findings rule out climate change, and implicate humans, as the primary extinction cause.

Description: Highlights: • Fungal infections represent an increasing threat to human health. • Fungal infections in plants are a worldwide problem to the agricultural industry. • Diverse antifungal compounds were isolated from different marine organisms. • The number of new antifungal marine natural products is rapidly developing. • Marine sponges and bacteria are the predominant sources for antifungal compounds. Abstract: Fungal diseases represent an increasing threat to human health worldwide which in some cases might be associated with substantial morbidity and mortality. However, only few antifungal drugs are currently available for the treatment of life-threatening fungal infections. Furthermore, plant diseases caused by fungal pathogens represent a worldwide economic problem for the agriculture industry. The marine environment continues to provide structurally diverse and biologically active secondary metabolites, several of which have inspired the development of new classes of therapeutic agents. Among these secondary metabolites, several compounds with noteworthy antifungal activities have been isolated from marine microorganisms, invertebrates, and algae. During the last fifteen years, around 65% of marine natural products possessing antifungal activities have been isolated from sponges and bacteria. This review gives an overview of natural products from diverse marine organisms that have shown in vitro and/or in vivo potential as antifungal agents, with their mechanism of action whenever applicable. The natural products literature is covered from January 2000 until June 2015, and we are reporting the chemical structures together with their biological activities, as well as the isolation source.

Description: New high-precision minor element analysis of the most magnesian olivine cores (Fo85–88) in fifteen high-MgO (Mg#66–74) alkali basalts or trachybasalts from the Quaternary backarc volcanic province, Payenia, of the Andean Southern Volcanic Zone in Argentina displays a clear north-to-south decrease in Mn/Feol. This is interpreted as the transition from mainly peridotite-derived melts in the north to mainly pyroxenite-derived melts in the south. The peridotite–pyroxenite source variation correlates with a transition of rock compositions from arc-type to OIB-type trace element signatures, where samples from the central part of the province are intermediate. The southernmost rocks have, e.g., relatively low La/Nb, Th/Nb and Th/La ratios as well as high Nb/U, Ce/Pb, Ba/Th and Eu/Eu* = 1.08. The northern samples are characterized by the opposite and have Eu/Eu* down to 0.86. Several incompatible trace element ratios in the rocks correlate with Mn/Feol and also reflect mixing of two geochemically distinct mantle sources. The peridotite melt end-member carries an arc signature that cannot solely be explained by fluid enrichment since these melts have relatively low Eu/Eu*, Ba/Th and high Th/La ratios, which suggest a component of upper continental crust (UCC) in the metasomatizing agent of the northern mantle. However, the addition to the mantle source of crustal materials or varying oxidation state cannot explain the variation in Mn and Mn/Fe of the melts and olivines along Payenia. Instead, the correlation between Mn/Feol and whole-rock (wr) trace element compositions is evidence of two-component mixing of melts derived from peridotite mantle source enriched by slab fluids and UCC melts and a pyroxenite mantle source with an EM1-type trace element signature. Very low Ca/Fe ratios (~1.1) in the olivines of the peridotite melt component and lower calculated partition coefficients for Ca in olivine for these samples are suggested to be caused by higher H2O contents in the magmas derived from subduction zone enriched mantle. Well-correlated Mn/Fe ratios in the wr and primitive olivines demonstrate that the Mn/Fewr of these basalts that only fractionated olivine and chromite reflects the Mn/Fe of the primitive melts and can be used as a proxy for the amount of pyroxenite melt in the magmas. Using Mn/Fewr for a large dataset of primitive Payenia rocks, we show that decreasing Mn/Fewr is correlated with decreasing Mn and increasing Zn/Mn as expected for pyroxenite melts.

Description: The Ontong Java and Manihiki oceanic plateaus are believed to have formed through high-degree melting of a mantle plume head. Boninite-like, low-Ti basement rocks at Manihiki, however, imply a more complex magma genesis compared with Ontong Java basement lavas that can be generated by ∼30% melting of a primitive mantle source. Here we show that the trace element and isotope compositions of low-Ti Manihiki rocks can best be explained by re-melting of an ultra-depleted source (possibly a common mantle component in the Ontong Java and Manihiki plume sources) re-enriched by ≤1% of an ocean-island-basalt-like melt component. Unlike boninites formed via hydrous flux melting of refractory mantle at subduction zones, these boninite-like intraplate rocks formed through adiabatic decompression melting of refractory plume material that has been metasomatized by ocean-island-basalt-like melts. Our results suggest that caution is required before assuming all Archaean boninites were formed in association with subduction processes.

Description: Male secondary sexual traits are targets of inter- and/or intrasexual selection, but can vary due to a correlation with life-history traits or as by-product of adaptation to distinct environments. Trade-offs contributing to this variation may comprise conspicuousness towards conspecifics versus inconspicuousness towards predators, or between allocating resources into coloration versus the immune system. Here, we examine variation in expression of a carotenoid-based visual signal, anal-fin egg-spots, along a replicate environmental gradient in the haplochromine cichlid fish Astatotilapia burtoni. We quantified egg-spot number, area, and coloration; applied visual models to estimate the trait's conspicuousness when perceived against the surrounding tissue under natural conditions; and used the lymphocyte ratio as a measure for immune activity. We find that (i) males possess larger and more conspicuous egg-spots than females, which is likely explained by their function in sexual selection; (ii) riverine fish generally feature fewer but larger and/or more intensively colored egg-spots, which is probably to maintain signal efficiency in intraspecific interactions in long-wavelength shifted riverine light conditions; and (iii) egg-spot number and relative area correlate with immune defense, suggesting a trade-off in the allocation of carotenoids. Taken together, haplochromine egg-spots feature the potential to adapt to the respective underwater light environment, and are traded-off with investment into the immune system

Description: MSM60 – Kapstadt /Südafrika nach Montevideo/Uruguay 1. Wochenbericht - Maria S Merian MSM60

Description: Different studies on the position of the non-indigenous species Neogobius melanostomus within the coastal food web of the Pomeranian Bay (western Baltic) were performed, resulting in a quantitative and qualitative species list of prey organisms found in the stomachs of the invader and an estimation concerning the importance of round goby as prey for different resident predators. It seems that the colonization process is not fully completed yet, but the results reveal that the species is already established in the food web 16 years after the first observation within the study area. The results show that N. melanostomus feed upon a wide range of different resident organisms. While a direct predation effect on native fish species appears rather unlikely, indirect effects such as competition cannot yet be excluded. In addition, our results reveal an ontogenetic diet shift and that the round goby itself already serves as an important prey for piscivorous fish and seabirds. Finally, we formulate different hypotheses based on our results which will require further research.

Description: The active volcanic island Tristan da Cunha, located at the southwestern and youngest end of the Walvis Ridge - Tristan/Gough hotspot track, is believed to be the surface expression of a huge thermal mantle anomaly. While several criteria for the diagnosis of a classical hotspot track are met, the Tristan region also shows some peculiarities. Consequently it is vigorously debated if the active volcanism in this region is the expression of a deep mantle plume, or if it is caused by shallow plate tectonics and the interaction with the nearby Mid-Atlantic Ridge. Because of a lack of geophysical data in the study area, no model or assumption has been completely confirmed. We present the first amphibian P-wave finite-frequency travel time tomography of the Tristan da Cunha region, based on cross-correlated travel time residuals of teleseismic earthquakes recorded by 24 ocean-bottom seismometers. The data can be used to image a low velocity structure southwest of the island. The feature is cylindrical with a radius of ~ 100 km down to a depth of 250 km. We relate this structure to the origin of Tristan da Cunha and name it the Tristan conduit. Below 250 km the low velocity structure ramifies into narrow veins, each with a radius of ~ 50 km. Furthermore, we imaged a linkage between young seamounts southeast of Tristan da Cunha and the Tristan conduit.

Description: The ocean's potential to export carbon to depth partly depends on the fraction of primary production (PP) sinking out of the euphotic zone (i.e., the e-ratio). Measurements of PP and export flux are often performed simultaneously in the field, although there is a temporal delay between those parameters. Thus, resulting e-ratio estimates often incorrectly assume an instantaneous downward export of PP to export flux. Evaluating results from four mesocosm studies, we find that peaks in organic matter sedimentation lag chlorophyll a peaks by 2 to 15 days. We discuss the implications of these time lags (TLs) for current e-ratio estimates and evaluate potential controls of TL. Our analysis reveals a strong correlation between TL and the duration of chlorophyll a buildup, indicating a dependency of TL on plankton food web dynamics. This study is one step further toward time-corrected e-ratio estimates

Description: Tectonically induced changes in oceanic seaways had profound effects on global and regional climate during the Late Neogene. The constriction of the Central American Seaway reached a critical threshold during the early Pliocene ~4.8–4 million years (Ma) ago. Model simulations indicate the strengthening of the Atlantic Meridional Overturning Circulation (AMOC) with a signature warming response in the Northern Hemisphere and cooling in the Southern Hemisphere. Subsequently, between ~4–3 Ma, the constriction of the Indonesian Seaway impacted regional climate and might have accelerated the Northern Hemisphere Glaciation. We here present Pliocene Atlantic interhemispheric sea surface temperature and salinity gradients (deduced from foraminiferal Mg/Ca and stable oxygen isotopes, δ18O) in combination with a recently published benthic stable carbon isotope (δ13C) record from the southernmost extent of North Atlantic Deep Water to reconstruct gateway-related changes in the AMOC mode. After an early reduction of the AMOC at ~5.3 Ma, we show in agreement with model simulations of the impacts of Central American Seaway closure a strengthened AMOC with a global climate signature. During ~3.8–3 Ma, we suggest a weakening of the AMOC in line with the global cooling trend, with possible contributions from the constriction of the Indonesian Seaway.

Description: MSM60 – Kapstadt /Südafrika nach Montevideo/Uruguay 3. Wochenbericht - Maria S Merian MSM60

Description: International Ocean Discovery Program (IODP) Expedition 352 recovered a high-fidelity record of volcanism related to subduction initiation in the Bonin fore-arc. Two sites (U1440 and U1441) located in deep water nearer to the trench recovered basalts and related rocks; two sites (U1439 and U1442) located in shallower water further from the trench recovered boninites and related rocks. Drilling in both areas ended in dolerites inferred to be sheeted intrusive rocks. The basalts apparently erupted immediately after subduction initiation and have compositions similar to those of the most depleted basalts generated by rapid sea-floor spreading at mid-ocean ridges, with little or no slab input. Subsequent melting to generate boninites involved more depleted mantle and hotter and deeper subducted components as subduction progressed and volcanism migrated away from the trench. This volcanic sequence is akin to that recorded by many ophiolites, supporting a direct link between subduction initiation, fore-arc spreading, and ophiolite genesis.

Description: (22.01.-30.01.2017)

Description: Maria S. Merian MSM61 (Mindelo – Las Palmas) 18.02.2017 - 27.02.2017 Tropischer Ostatlantik

Description: Highlights: • Improved Claisen-Schmidt condensation using lithium hydroxide monohydrate in 1,4-dioxane. • Pyridylchalcones show good activity and selectivity against Trypanosoma brucei. • Pyridylchalcones show little activity against Leishmania donovani. • Promising leads in the development of novel compounds for the treatment of sleeping sickness. A library of novel pyridylchalcones were synthesised and screened against Trypanosoma brucei rhodesiense. Eight were shown to have good activity with the most potent 8 having an IC50 value of 0.29 μM. Cytotoxicity testing with human KB cells showed a good selectivity profile for this compound with a selectivity index of 47. Little activity was seen when the library was tested against Leishmania donovani. In conclusion, pyridylchalcones are promising leads in the development of novel compounds for the treatment of human African trypanosomiasis (HAT).

Description: Plankton communities play a key role in the marine food web and are expected to be highly sensitive to ongoing environmental change. Oceanic uptake of anthropogenic carbon dioxide (CO2) causes pronounced shifts in marine carbonate chemistry and a decrease in seawater pH. These changes–summarized by the term ocean acidification (OA)–can significantly affect the physiology of planktonic organisms. However, studies on the response of entire plankton communities to OA, which also include indirect effects via food-web interactions, are still relatively rare. Thus, it is presently unclear how OA could affect the functioning of entire ecosystems and biogeochemical element cycles. In this study, we report from a long-term in situ mesocosm experiment, where we investigated the response of natural plankton communities in temperate waters (Gullmarfjord, Sweden) to elevated CO2 concentrations and OA as expected for the end of the century (~760 μatm pCO2). Based on a plankton-imaging approach, we examined size structure, community composition and food web characteristics of the whole plankton assemblage, ranging from picoplankton to mesozooplankton, during an entire winter-to-summer succession. The plankton imaging system revealed pronounced temporal changes in the size structure of the copepod community over the course of the plankton bloom. The observed shift towards smaller individuals resulted in an overall decrease of copepod biomass by 25%, despite increasing numerical abundances. Furthermore, we observed distinct effects of elevated CO2 on biomass and size structure of the entire plankton community. Notably, the biomass of copepods, dominated by Pseudocalanus acuspes, displayed a tendency towards elevated biomass by up to 30–40% under simulated ocean acidification. This effect was significant for certain copepod size classes and was most likely driven by CO2-stimulated responses of primary producers and a complex interplay of trophic interactions that allowed this CO2 effect to propagate up the food web. Such OA-induced shifts in plankton community structure could have far-reaching consequences for food-web interactions, biomass transfer to higher trophic levels and biogeochemical cycling of marine ecosystems.

Description: Dates of the cruise: from 06.08.2016 to 25.08.2016 Areas of Research: methane chemistry, molecular biology, planktology Dates and names of Ports of call: Ventspils (Latvia). 15-18 August 2016

Description: The sediment-water interface is an important site for material exchange in marine systems and harbor unique microbial habitats. The flux of nutrients, metals, and greenhouse gases at this interface may be severely dampened by the activity of microorganisms and abiotic redox processes, leading to the “benthic filter” concept. In this study, we investigate the spatial variability, mechanisms and quantitative importance of a microbially-dominated benthic filter for dissolved sulfide in the Eastern Gotland Basin (Baltic Sea) that is located along a dynamic redox gradient between 65 and 173 m water depth. In August-September 2013, high resolution (0.25 mm minimum) vertical microprofiles of redox-sensitive species were measured in surface sediments with solid-state gold-amalgam voltammetric microelectrodes. The highest sulfide consumption (2.73–3.38 mmol m−2 day−1) occurred within the top 5 mm in sediments beneath a pelagic hypoxic transition zone (HTZ, 80–120 m water depth) covered by conspicuous white bacterial mats of genus Beggiatoa. A distinct voltammetric signal for polysulfides, a transient sulfur oxidation intermediate, was consistently observed within the mats. In sediments under anoxic waters (〉140 m depth), signals for Fe(II) and aqueous FeS appeared below a subsurface maximum in dissolved sulfide, indicating a Fe(II) flux originating from older sediments presumably deposited during the freshwater Ancylus Lake that preceded the modern Baltic Sea. Our results point to a dynamic benthic sulfur cycling in Gotland Basin where benthic sulfide accumulation is moderated by microbial sulfide oxidation at the sediment surface and FeS precipitation in deeper sediment layers. Upscaling our fluxes to the Baltic Proper; we find that up to 70% of the sulfide flux (2281 kton yr−1) toward the sediment-seawater interface in the entire basin can be consumed at the microbial mats under the HTZ (80–120 m water depth) while only about 30% the sulfide flux effuses to the bottom waters (〉120 m depth). This newly described benthic filter for the Gotland Basin must play a major role in limiting the accumulation of sulfide in and around the deep basins of the Baltic Sea.

Description: Using outdoor mesocosms we investigated the relative importance of the direct and indirect (here: altered grazing) effects of seawater warming on benthic microalgae in a Baltic Sea Fucus vesiculosus (Phaeophyceae) system during the spring season. Seawater warming had a positive main effect on microalgal total biomass accrual and growth rate and on total mesograzer abundance and biomass. Moreover, under the existing resource-replete conditions in spring the direct positive effect of warming on microalgae was stronger than its indirect negative effect through enhanced grazing. The outcome of this study contrasts previous observations from the summer and winter season, where indirect effects of warming mediated by altered grazing were identified as an important driver of primary biomass in the Fucus system. In this context, the results from the spring season add mechanistic information to the overall understanding of the seasonal variability of climate change effects. They suggest that the relative importance of the underlying direct and indirect effective pathways of warming and the overall effect on the balance between production and consumption are influenced by the trophic state of the system, which in temperate regions is related to season.

Description: (13.03. – 19.03.2017)

Description: Stable isotope compositions can potentially be used to trace atmospheric Cd inputs to the surface ocean and anthropogenic Cd emissions to the atmosphere. Both of these applications may provide valuable insights into the effects of anthropogenic activities on the cycling of Cd in the environment. However, a lack of constraints for the Cd isotope compositions of atmospheric aerosols is currently hindering such studies. Here, we present stable Cd isotope data for aerosols collected over the Tropical Atlantic Ocean. The samples feature variable proportions of mineral dust-derived and anthropogenic Cd, yet exhibit similar isotope compositions, thus negating the distinction of these Cd sources using isotopic signatures in this region. Isotopic variability between these two atmospheric Cd sources may be identified in other areas, and thus warrants further investigation. Regardless, these data provide important initial constraints on the isotope composition of atmospheric Cd inputs to the ocean.

Description: Aim: The lives of juvenile leatherback turtles are amongst the most enigmatic of all marine mega-vertebrates. For these cryptic organisms, ocean models provide important insights into their dispersion from natal sites. Here, corroborated by fisheries bycatch data, we simulate spatio-temporal variation in hatchling dispersion patterns over five decades from the World's largest leatherback turtle nesting region. Location: Equatorial Central West Africa (3.5°N to −6°S) spanning the Gulf of Guinea in the North, Gabon and the Republic/Democratic Republic of the Congo in the South. Results: Due to dynamic oceanic conditions at these equatorial latitudes, dispersion scenarios differed significantly: (1) along the north to south gradient of the study region, (2) seasonally and (3) between years. From rookeries to the north of the equator, simulated hatchling retention rates within the Gulf of Guinea were very high (〉99%) after 6 months of drift, whilst south of the equator, retention rates were as low as c. 6% with the majority of simulated hatchlings dispersing west into the South Atlantic Ocean with the South Equatorial Current. Seasonal dispersion variability was driven by wind changes arising from the yearly north/southward migration of the intertropical convergence zone resulting in the increasing westerly dispersion of hatchlings throughout the hatching season. Annual variability in wind stress drove a long-term trend for decreased retention within the Gulf of Guinea and increased westerly dispersion into habitats in the South Atlantic Ocean. Main conclusions: Shifts in dispersion habitats arising from spatio-temporal oceanic variability expose hatchlings to different environments and threats that will influence important life history attributes such as juvenile growth/survival rates; anticipated to impact the population dynamics and size/age structure of populations into adulthood. The impacts of local and dynamic oceanic conditions thus require careful considerations, such as subregional management, when managing marine populations of conservation concern.

Description: (20.03. – 26.03.2017)

Description: (19.03.17‐26.03.17)

Description: Wochenbericht Li17_03 (vom 20.03. – 25.03)

Description: The production of shiga toxin (Stx) is a critical step in the establishment and progress of enterohemorrhagic Escherichia coli (EHEC) infections. The possible release of Stx from dead and dying bacteria, and the risk of resistance development have restricted the usage of antibiotics against EHEC. The chlorinated quaternary ammonium compound, strepthonium A, was isolated from the culture of Streptomyces sp. SBT345 that was cultivated from the Mediterranean sponge Agelas oroides. The structure was elucidated and confirmed by spectroscopic analyses including 1D and 2D NMR, ESI-HRMS, as well as ESI-HRMS2. Strepthonium A follows Lipinski's rule of five with respect to its molecular weight, CLogP values and the number of hydrogen acceptors and donors. Verotoxin ELISA assay demonstrated that Strepthonium A reduced the Stx production in EHEC strain EDL933 at 80 μM concentration without growth inhibition. This study demonstrates the potential of strepthonium A in restraining the production of Stx in EHEC infections.

Description: The waning stage(s) of the Tethyan ocean(s) in the Balkans are not well understood. Controversy centres on the origin and life-span of the Cretaceous Sava Zone, which is allegedly a remnant of the last oceanic domain in the Balkan Peninsula, defining the youngest suture between Eurasia- and Adria-derived plates. In order to investigate to what extent late-Cretaceous volcanism within the Sava zone is consistent with this model, we present new age data together with trace-element and Sr–Nd–Pb isotope data for the Klepa basaltic lavas from the central Balkan Peninsula. Our new geochemical data show marked differences between the Cretaceous Klepa basalts (Sava Zone) and the rocks of other volcanic sequences from the Jurassic ophiolites of the Balkans. The Klepa basalts mostly have Sr–Nd–Pb isotopic and trace-element signatures that resemble enriched within-plate basalts, substantially different from Jurassic ophiolite basalts with MORB, BAB and IAV affinities. Trace-element modelling of the Klepa rocks indicates 2–20% polybaric melting of a relatively homogeneously metasomatised mantle source that ranges in composition from garnet lherzolite to ilmenite+apatite bearing spinel–amphibole lherzolite. Thus, the residual mineralogy is characteristic of a continental rather than oceanic lithospheric mantle source, suggesting an intracontinental within-plate origin for the Klepa basalts. Two alternative geodynamic models are internally consistent with our new findings: i) if the Sava Zone represents remnants of the youngest Neotethyan Ocean, magmatism along this zone would be situated within the forearc region and triggered by ridge subduction; ii) if the Sava Zone delimits a diffuse tectonic boundary between Adria and Europe, which had already collided in the Late Jurassic, the Klepa basalts together with a number of other magmatic centres represent volcanism related to transtensional tectonics.

Description: Enhanced atmospheric input of dust-borne nutrients and minerals to the remote surface ocean can potentially increase carbon uptake and sequestration at depth. Nutrients can enhance primary productivity, and mineral particles act as ballast, increasing sinking rates of particulate organic matter. Here we present a two-year time series of sediment trap observations of particulate organic carbon flux to 3,000 m depth, measured directly in two locations: the dust-rich central North Atlantic gyre and the dust-poor South Atlantic gyre. We find that carbon fluxes are twice as high and a higher proportion of primary production is exported to depth in the dust-rich North Atlantic gyre. Low stable nitrogen isotope ratios suggest that high fluxes result from the stimulation of nitrogen fixation and productivity following the deposition of dust-borne nutrients. Sediment traps in the northern gyre also collected intact colonies of nitrogen-fixing Trichodesmium species. Whereas ballast in the southern gyre is predominantly biogenic, dust-derived mineral particles constitute the dominant ballast element during the enhanced carbon fluxes in the northern gyre. We conclude that dust deposition increases carbon sequestration in the North Atlantic gyre through the fertilization of the nitrogen-fixing community in surface waters and mineral ballasting of sinking particles

Description: In 2013, high-temperature vent fluids were sampled in the Nifonea vent field. This field is located within the caldera of a large shield-type volcano of the Vate Trough, a young extensional rift in the New Hebrides back-arc. Hydrothermal venting occurs as clear and black smoker fluids with temperatures up to 368 °C, the hottest temperatures measured so far in the western Pacific. The physico-chemical conditions place the fluids within the two-phase field of NaCl–H2O, and venting is dominated by vapour phase fluids with Cl concentrations as low as 25 mM. The fluid composition, which differs between the individual vent sites, is interpreted to reflect the specific geochemical fluid signature of a hydrothermal system in its initial, post-eruptive stage. The strong Cl depletion is accompanied by low alkali/Cl ratios compared to more evolved hydrothermal systems, and very high Fe/Cl ratios. The concentrations of REY (180 nM) and As (21 μM) in the most Cl-depleted fluid are among the highest reported so far for submarine hydrothermal fluids, whereas the inter-element REY fractionation is only minor. The fluid signature, which has been described here for the first time in a back-arc setting, is controlled by fast fluid passage through basaltic volcanic rocks, with extremely high water-rock ratios and only limited water-rock exchange, phase separation and segregation, and (at least) two-component fluid mixing. Metals and metalloids are unexpectedly mobile in the vapour phase fluids, and the strong enrichments of Fe, REY, and As highlight the metal transport capacity of low-salinity, low-density vapours at the specific physico-chemical conditions at Nifonea. One possible scenario is that the fluids boiled before the separated vapour phase continued to react with fresh glassy lavas. The mobilization of metals is likely to occur by leaching from fresh glass and grain boundaries and is supported by the high water/rock ratios. The enrichment of B and As is further controlled by their high volatility, whereas the strong enrichment of REY is also a consequence of the elevated concentrations in the host rocks. However, a direct contribution of metals such as As from magmatic degassing cannot be ruled out. The different fluid end-member composition of individual vent sites could be explained by mixing of vapour phase fluids with another fluid phase of different water/rock interaction history.

Description: The upstream sources and pathways of the Denmark Strait Overflow Water and their variability have been investigated using a high-resolution model hindcast. This global simulation covers the period from 1948 to 2009 and uses a fine model mesh (1/20°) to resolve mesoscale features and the complex current structure north of Iceland explicitly. The three sources of the Denmark Strait Overflow, the shelfbreak East Greenland Current (EGC), the separated EGC, and the North Icelandic Jet, have been analyzed using Eulerian and Lagrangian diagnostics. The shelfbreak EGC contributes the largest fraction in terms of volume and freshwater transport to the Denmark Strait Overflow and is the main driver of the overflow variability. The North Icelandic Jet contributes the densest water to the Denmark Strait Overflow and shows only small temporal transport variations. During summer, the net volume and freshwater transports to the south are reduced. On interannual time scales, these transports are highly correlated with the large-scale wind stress curl around Iceland and, to some extent, influenced by the North Atlantic Oscillation, with enhanced southward transports during positive phases. The Lagrangian trajectories support the existence of a hypothesized overturning loop along the shelfbreak north of Iceland, where water carried by the North Icelandic Irminger Current is transformed and feeds the North Icelandic Jet. Monitoring these two currents and the region north of the Iceland shelfbreak could provide the potential to track long-term changes in the Denmark Strait Overflow and thus also the AMOC.

Description: Land-use dynamic is a major challenge for town and country planners especially in developing countries such as Iran. Iran has been under rapid urban expansion and population growth for past three decades which led to lack of resources, environmental deterioration and haphazard landscape development. In this paper, an attempt has been made to map the urbanization dynamics of Tehran in 40 years based on remote sensing imagery and by means of artificial neural networks. The presented scheme could be taken into consideration when planning initiatives aimed at surveying, monitoring, managing and sustainable development of the territory. Moreover, it can serve the experts in the fields of geography, urban studies and planning as a background for number of geographical analyses.

Description: Coccolithophores, a globally distributed group of marine phytoplankton, showed diverse responses to ocean acidification (OA) and to combinations of OA with other environmental factors. While their growth can be enhanced and calcification be hindered by OA under constant indoor light, fluctuation of solar radiation with ultraviolet irradiances might offset such effects. In this study, when a calcifying and a non-calcifying strain of Emiliania huxleyi were grown at 2 CO2 concentrations (low CO2 [LC]: 395 µatm; high CO2 [HC]: 1000 µatm) under different levels of incident solar radiation in the presence of ultraviolet radiation (UVR), HC and increased levels of solar radiation acted synergistically to enhance the growth in the calcifying strain but not in the non-calcifying strain. HC enhanced the particulate organic carbon (POC) and nitrogen (PON) productions in both strains, and this effect was more obvious at high levels of solar radiation. While HC decreased calcification at low solar radiation levels, it did not cause a significant effect at high levels of solar radiation, implying that a sufficient supply of light energy can offset the impact of OA on the calcifying strain. Our data suggest that increased light exposure, which is predicted to happen with shoaling of the upper mixing layer due to progressive warming, could counteract the impact of OA on coccolithophores distributed within this layer.

Description: The impact of anthropogenic ocean acidification (OA) on marine ecosystems is a vital concern facing marine scientists and managers of ocean resources. Euthecosomatous pteropods (holoplanktonic gastropods) represent an excellent sentinel for indicating exposure to anthropogenic OA because of the sensitivity of their aragonite shells to the OA conditions less favorable for calcification. However, an integration of observations, experiments and modelling efforts is needed to make accurate predictions of how these organisms will respond to future changes to their environment. Our understanding of the underlying organismal biology and life history is far from complete and must be improved if we are to comprehend fully the responses of these organisms to the multitude of stressors in their environment beyond OA. This review considers the present state of research and understanding of euthecosomatous pteropod biology and ecology of these organisms and considers promising new laboratory methods, advances in instrumentation (such as molecular, trace elements, stable isotopes, palaeobiology alongside autonomous sampling platforms, CT scanning and high-quality video recording) and novel field-based approaches (i.e. studies of upwelling and CO2 vent regions) that may allow us to improve our predictive capacity of their vulnerability and/or resilience. In addition to playing a critical ecological and biogeochemical role, pteropods can offer a significant value as an early-indicator of anthropogenic OA. This role as a sentinel species should be developed further to consolidate their potential use within marine environmental management policy making.

Description: Nitrous oxide (N2O) is a powerful greenhouse gas principally produced by nitrification and denitrification in the marine environment. Observations were made in the eastern South Pacific (ESP), between 10° and 60°S, and ~75°–88°W, from intermediate waters targeting Antarctic Intermediate Water (AAIW) at potential density of 27.0–27.1 kg m−3. Between 60° and 20°S, a gradual equatorward increase of N2O from 8 to 26 nmol L−1 was observed at density 27.0–27.1 kg m−3 where AAIW penetrates. Positive correlations were found between apparent N2O production (ΔN2O) and O2 utilization (AOU), and between ΔN2O and NO−3, which suggested that local N2O production is predominantly produced by nitrification. Closer to the equator, between 20° and 10°S at AAIW core, a strong N2O increase up to 75 nmol L−1 was observed. Because negative correlations were found between ΔN2O vs. NO−3 and ΔN2O vs. N* (a Nitrogen deficit index) and because ΔN2O and AOU do not follow a linear trend, we suspect that, in addition to nitrification, denitrification also takes place in N2O cycling. By making use of water mass mixing analyses, we show that an increase in N2O occurs in the region where high oxygen from AAIW merges with low oxygen from Equatorial Subsurface Water (ESSW), creating favorable conditions for local N2O production. We conclude that the non-linearity in the relationship between N2O and O2 is a result of mixing between two water masses with very different source characteristics, paired with the different time frames of nitrification and denitrification processes that impact water masses en route before they finally meet and mix in the ESP region.

Description: The microbial community response to petroleum seepage was investigated in a whole round sediment core (16 cm length) collected nearby natural hydrocarbon seepage structures in the Caspian Sea, using a newly developed Sediment-Oil-Flow-Through (SOFT) system. Distinct redox zones established and migrated vertically in the core during the 190 days-long simulated petroleum seepage. Methanogenic petroleum degradation was indicated by an increase in methane concentration from 8 μM in an untreated core compared to 2300 μM in the lower sulfate-free zone of the SOFT core at the end of the experiment, accompanied by a respective decrease in the δ13C signal of methane from -33.7 to -49.5‰. The involvement of methanogens in petroleum degradation was further confirmed by methane production in enrichment cultures from SOFT sediment after the addition of hexadecane, methylnapthalene, toluene, and ethylbenzene. Petroleum degradation coupled to sulfate reduction was indicated by the increase of integrated sulfate reduction rates from 2.8 SO42-m-2 day-1 in untreated cores to 5.7 mmol SO42-m-2 day-1 in the SOFT core at the end of the experiment, accompanied by a respective accumulation of sulfide from 30 to 447 μM. Volatile hydrocarbons (C2–C6 n-alkanes) passed through the methanogenic zone mostly unchanged and were depleted within the sulfate-reducing zone. The amount of heavier n-alkanes (C10–C38) decreased step-wise toward the top of the sediment core and a preferential degradation of shorter (〈C14) and longer chain n-alkanes (〉C30) was seen during the seepage. This study illustrates, to the best of our knowledge, for the first time the development of methanogenic petroleum degradation and the succession of benthic microbial processes during petroleum passage in a whole round sediment core.

Description: The North Atlantic Current (NAC) is subject to variability on multiannual to decadal time scales, influencing the transport of volume, heat, and freshwater from the subtropical to the eastern subpolar North Atlantic (NA). Current observational time series are either too short or too episodic to study the processes involved. Here we compare the observed continuous NAC transport time series at the western flank of the Mid-Atlantic Ridge (MAR) and repeat hydrographic measurements at the OVIDE line in the eastern Atlantic with the NAC transport and circulation in the high-resolution (1/20°) ocean model configuration VIKING20 (1960–2008). The modeled baroclinic NAC transport relative to 3400 m (24.5 ± 7.1 Sv) at the MAR is only slightly lower than the observed baroclinic mean of 27.4 ± 4.7 Sv from 1993 to 2008, and extends further north by about 0.5°. In the eastern Atlantic, the western NAC (WNAC) carries the bulk of the transport in the model, while transport estimates based on hydrographic measurements from five repeated sections point to a preference for the eastern NAC (ENAC). The model is able to simulate the main features of the subpolar NA, providing confidence to use the model output to analyze the influence of the North Atlantic Oscillation (NAO). Model based velocity composites reveal an enhanced NAC transport across the MAR of up to 6.7 Sv during positive NAO phases. Most of that signal (5.4 Sv) is added to the ENAC transport, while the transport of the WNAC was independent of the NAO.

Description: Anthropogenic atmospheric loading of CO2 raises concerns about combined effects of increasing ocean temperature and acidification, on biological processes. In particular, the response of appendicularian zooplankton to climate change may have significant ecosystem implications as they can alter biogeochemical cycling compared to classical copepod dominated food webs. However, the response of appendicularians to multiple climate drivers and effect on carbon cycling are still not well understood. Here, we investigated how gelatinous zooplankton (appendicularians) affect carbon cycling of marine food webs under conditions predicted by future climate scenarios. Appendicularians performed well in warmer conditions and benefited from low pH levels, which in turn altered the direction of carbon flow. Increased appendicularians removed particles from the water column that might otherwise nourish copepods by increasing carbon transport to depth from continuous discarding of filtration houses and fecal pellets. This helps to remove CO2 from the atmosphere, and may also have fisheries implications.

Description: Highlights • Crustal structure of Walvis Ridge reveals high seismic velocities in the lower crust intruding the African continent. • This modified crust is localized to approx. 100 × 100 km within the continent. • No indication for a large plume head observed The opening of the South Atlantic is a classical example for a plume related continental breakup. Flood basalts are present on both conjugate margins as well as aseismic ridges connecting them with the current plume location at Tristan da Cunha. To determine the effect of the proposed plume head on the continental crust, we acquired wide-angle seismic data at the junction of the Walvis Ridge with the African continent and modelled the P-wave velocity structure in a forward approach. The profile extends 430. km along the ridge and continues onshore to a length of 720. km. Crustal velocities beneath the Walvis Ridge vary between 5.5. km/s and 7.0. km/s, a typical range for oceanic crust. The crustal thickness of 22. km, however, is approximately three times larger than of normal oceanic crust. The continent-ocean transition is characterized by 30. km thick crust with strong lateral velocity variations in the upper crust and a high-velocity lower crust (HVLC), where velocities reach up to 7.5. km/s. The HVLC is 100 to 130. km wider at the Walvis Ridge than it is farther south, and impinges onto the continental crust of the Kaoko fold belt. Such high seismic velocities indicate Mg-rich igneous material intruded into the continental crust during the initial rifting stage. However, the remaining continental crust seems unaffected by intrusions and the root of the 40. km-thick crust of the Kaoko belt is not thermally abraded. We conclude that the plume head did not modify the continental crust on a large scale, but caused rather local effects. Thus, it seems unlikely that a plume drove or initiated the breakup process. We further propose that the plume already existed underneath the continent prior to the breakup, and ponded melt erupted at emerging rift structures providing the magma for continental flood basalts.

Description: Folate-mediated one-carbon metabolism (FOCM) is an interconnected network of metabolic pathways, including those required for the de novo synthesis of dTMP and purine nucleotides and for remethylation of homocysteine to methionine. Mouse models of folate-responsive neural tube defects (NTDs) indicate that impaired de novo thymidylate (dTMP) synthesis through changes in SHMT expression is causative in folate-responsive NTDs. We have created a hybrid computational model comprised of ordinary differential equations and stochastic simulation. We investigated whether the de novo dTMP synthesis pathway was sensitive to perturbations in FOCM that are known to be associated with human NTDs. This computational model shows that de novo dTMP synthesis is highly sensitive to the common MTHFR C677T polymorphism and that the effect of the polymorphism on FOCM is greater in folate deficiency. Computational simulations indicate that the MTHFR C677T polymorphism and folate deficiency interact to increase the stochastic behavior of the FOCM network, with the greatest instability observed for reactions catalyzed by serine hydroxymethyltransferase (SHMT). Furthermore, we show that de novo dTMP synthesis does not occur in the cytosol at rates sufficient for DNA replication, supporting empirical data indicating that impaired nuclear de novo dTMP synthesis results in uracil misincorporation into DNA.

Description: Species distribution modelling can be applied to identify potentially suitable habitat for species with largely unknown distributions, such as many deep-water corals. Important variables influencing species occurrence in the deep sea, e.g. substrate composition, are often not included in these modelling approaches because high-resolution data are unavailable. We investigated the relationship between substrate composition and the occurrence of the two deep-water octocoral species Primnoa resedaeformis and Paragorgia arborea, which require hard substrate for attachment. On a scale of 10s of metres, we analysed images of the seafloor taken at two locations inside the Northeast Channel Coral Conservation Area in the Northwest Atlantic. We interpolated substrate composition over the sampling areas and determined the contribution of substrate classes, depth and slope to describe habitat suitability using maximum entropy modelling (Maxent). Substrate composition was similar at both sites - dominated by pebbles in a matrix of sand (〉80%) with low percentages of suitable substrate for coral occurrence. Coral abundance was low at site 1 (0.9 colonies of P. resedaeformis per 100m2) and high at site 2 (63 colonies of P. resedaeformis per 100m2) indicating that substrate alone is not sufficient to explain varying patterns in coral occurrence. Spatial interpolations of substrate classes revealed the difficulty to accurately resolve sparsely distributed boulders (3-5% of substrate). Boulders were by far the most important variable in the habitat suitability model (HSM) for P. resedaeformis at site 1, indicating the fundamental influence of a substrate class that is the least abundant. At site 2, HSMs identified cobbles and sand/pebble as the most important variables for habitat suitability. However, substrate classes were correlated making it difficult to determine the influence of individual variables. To provide accurate information on habitat suitability for the two coral species, substrate composition needs to be quantified so that small fractions (〈20% contribution of certain substrate class) of suitable substrate are resolved. While the collection and analysis of high-resolution data is costly and spatially limited, the required resolution is unlikely to be achieved in coarse-scale interpolations of substrate data.

Description: The late-Holocene expansion of the Tupi–Guarani languages from southern Amazonia to SE South America constitutes one of the largest expansions of any linguistic family in the world, spanning ~4000 km between latitudes 0°S and 35°S at about 2.5k cal. yr BP. However, the underlying reasons for this expansion are a matter of debate. Here, we compare continental-scale palaeoecological, palaeoclimate and archaeological datasets, to examine the role of climate change in facilitating the expansion of this forest-farming culture. Because this expansion lies within the path of the South American Low-Level Jet, the key mechanism for moisture transport across lowland South America, we were able to explore the relationship between climate change, forest expansion and the Tupi–Guarani. Our data synthesis shows broad synchrony between late-Holocene increasing precipitation and southerly expansion of both tropical forest and Guarani archaeological sites – the southernmost branch of the Tupi–Guarani. We conclude that climate change likely facilitated the agricultural expansion of the Guarani forest-farming culture by increasing the area of forested landscape that they could exploit, showing a prime example of ecological opportunism.

Description: Highlights • A rapid automated analytical method for simultaneous analysis of multiple trace metals in small volumes of seawater. • Isotope dilution is utilized for concentration quantification, eliminating sensitivity to variation in recovery. • Minimal variability in automated sample loading and elution volumes allows precise quantification via standard addition for monoisotopic elements. • High accuracy was confirmed by analysis of reference seawaters SAFe S, D1 and D2. • The utilized resin (WAKO) demonstrated improved recoveries for most tested trace metals in comparison to a NOBIAS Chelate-PA1 resin. A rapid, automated, high-throughput analytical method capable of simultaneous analysis of multiple elements at trace and ultratrace levels is required to investigate the biogeochemical cycle of trace metals in the ocean. Here we present an analytical approach which uses a commercially available automated preconcentration device (SeaFAST) with accurate volume loading and in-line pH buffering of the sample prior to loading onto a chelating resin (WAKO) and subsequent simultaneous analysis of iron (Fe), zinc (Zn), copper (Cu), nickel (Ni), cadmium (Cd), lead (Pb), cobalt (Co) and manganese (Mn) by high-resolution inductively-coupled plasma mass spectrometry (HR-ICP-MS). Quantification of sample concentration was undertaken using isotope dilution for Fe, Zn, Cu, Ni, Cd and Pb, and standard addition for Co and Mn. The chelating resin is shown to have a high affinity for all analyzed elements, with recoveries between 83 and 100% for all elements, except Mn (60%) and Ni (48%), and showed higher recoveries for Ni, Cd, Pb, Co and Mn in direct comparison to an alternative resin (NOBIAS Chelate-PA1). The reduced recoveries for Ni and Mn using the WAKO resin did not affect the quantification accuracy. A relatively constant retention efficiency on the resin over a broad pH range (pH 5–8) was observed for the trace metals, except for Mn. Mn quantification using standard addition required accurate sample pH adjustment with optimal recoveries at pH 7.5 ± 0.3. UV digestion was necessary to increase recovery of Co and Cu in seawater by 15.6% and 11.4%, respectively, and achieved full break-down of spiked Co-containing vitamin B12 complexes. Low blank levels and detection limits could be achieved (e.g., 0.029 nmol L⁻¹ for Fe and 0.028 nmol L⁻¹ for Zn) with the use of high purity reagents. Precision and accuracy were assessed using SAFe S, D1, and D2 reference seawaters, and results were in good agreement with available consensus values. The presented method is ideal for high throughput simultaneous analysis of trace elements in coastal and oceanic seawaters. We present a successful application of the analytical method to samples collected in June 2014 in the Northeast Atlantic Ocean.

Description: Die Weltmeere sind die Grundlage unserer Existenz und unsere wichtigste Ressource. Und sie sind der Ursprung allen Lebens auf der Erde, eine faszinierende und viel- fach noch völlig unbekannte Welt, deren Zerstörung seit Jahren ungeahnte Ausmaße erreicht hat. Mojib Latif, der renommierte Klima- und Meeresforscher geht in seinem Buch existenziellen Fragen nach: Welche Rolle spielen die Ozeane beim Klimawandel? Welche Konsequenzen folgen aus der Versauerung der Ozeane? Wohin führt die Verschmutzung durch Erdöl? Wie ist die Rolle des Plastikmülls einzuschätzen? Und wie die Belastung durch Radioaktivität? Mojib Latif präsentiert ein eindringliches Plädoyer für die Erhaltung unserer Lebensgrundlage, dem man sich kaum entziehen kann.

Description: The solubility of water in a basaltic and in an andesitic melt has been determined in the pressure range from approximately 1,000 to 6,000 bars at 1,100° C. The solubility in basaltic melt is 3.1 weight percent at 1,000 bars and 9.4 weight percent at 6,000 bars; in the andesitic melt it is 4.5 weight percent at 1,000 bars and 10.1 weight percent at 5,300 bars. The temperatures of appearance of the primary, secondary, and tertiary phases in the basalt have been determined at 1,000 bars water pressure and at the fo2's of the magnetite+hematite (MH), magnetite+fayalite+quartz (MFQ) and magnetite+wüstite (MW) buffers. Results are as follows: Buffer Pyroxene Plagioclase Ore mineral MH 1,095°C 1,065°C 1,230°C MFQ 1,040° 1,015° 1,010° MW 1,020° 1,010° 995° A comparison of the solubility of water at 1,100°C and up to approximately 6,000 bars pressure in several silicate melts, ranging in composition from granitic to gabbroic, indicates that the spread of solubility is narrower than has been supposed. The marked effect of fo2's on the crystallization sequence in the Columbia River basalt confirms the importance of this factor in determining liquid lines of descent. In experiments with low fo2's (MW buffer) and 1,000 bars water pressure, the basalt was completely liquid at the relatively low temperature of 1,020° C.

Description: While the Earth's surface has considerably warmed over the past two decades, the tropical Pacific has featured a cooling of sea surface temperatures in its eastern and central parts, which went along with an unprecedented strengthening of the equatorial trade winds, the surface component of the Pacific Walker Circulation (PWC). Previous studies show that this decadal trend in the trade winds is generally beyond the range of decadal trends simulated by climate models when forced by historical radiative forcing. There is still a debate on the origin of and the potential role that internal variability may have played in the recent decadal surface wind trend. Using a number of long control (unforced) integrations of global climate models and several observational data sets, we address the question as to whether the recent decadal to multidecadal trends are robustly classified as an unusual event or the persistent response to external forcing. The observed trends in the tropical Pacific surface climate are still within the range of the long-term internal variability spanned by the models but represent an extreme realization of this variability. Thus, the recent observed decadal trends in the tropical Pacific, though highly unusual, could be of natural origin. We note that the long-term trends in the selected PWC indices exhibit a large observational uncertainty, even hindering definitive statements about the sign of the trends.

Description: Accurate pH measurements in polar waters and sea ice brines require pH indicator dyes characterized at near-zero and below-zero temperatures and high salinities. We present experimentally determined physical and chemical characteristics of purified meta-Cresol Purple (mCP) pH indicator dye suitable for pH measurements in seawater and conservative seawater-derived brines at salinities (S) between 35 and 100 and temperatures (T) between their freezing point and 298.15 K (25 °C). Within this temperature and salinity range, using purified mCP and a novel thermostated spectrophotometric device, the pH on the total scale (pHT) can be calculated from direct measurements of the absorbance ratio R of the dye in natural samples as pHT=−log(kT2e2)+log(R−e11−Re3e2) Based on the mCP characterization in these extended conditions, the temperature and salinity dependence of the molar absorptivity ratios and − log(kT2e2) of purified mCP is described by the following functions: e1 = −0.004363 + 3.598 × 10−5T, e3/e2 = −0.016224 + 2.42851 × 10−4T + 5.05663 × 10−5(S − 35), and − log(kT2e2) = −319.8369 + 0.688159 S −0.00018374 S2 + (10508.724 − 32.9599 S + 0.059082S2) T−1 + (55.54253 − 0.101639 S) ln T −0.08112151T. This work takes the characterisation of mCP beyond the currently available ranges of 278.15 K ≤ T ≤ 308.15 K and 20 ≤ S ≤ 40 in natural seawater, thereby allowing high quality pHT measurements in polar systems.

Description: Biodiversity and conservation data are generally costly to collect, particularly in the marine realm. Hence, data collected for a given—often scientific—purpose are occasionally contributed toward secondary needs, such as policy implementation or other types of decision-making. However, while the quality and accessibility of marine biodiversity and conservation data have improved over the past decade, the ways in which these data can be used to develop and implement relevant management and conservation measures and actions are not always explicit. For this reason, there are a number of scientifically-sound datasets that are not used systematically to inform policy and decisions. Transforming these marine biodiversity and conservation datasets into knowledge products that convey the information required by policy- and decision-makers is an important step in strengthening knowledge exchange across the science-policy interface. Here, we identify seven characteristics of a selection of online biodiversity and conservation knowledge products that contribute to their ability to support policy- and decision-making in the marine realm (as measured by e.g., mentions in policy resolutions/decisions, or use for reporting under selected policy instruments; use in high-level screening for areas of biodiversity importance). These characteristics include: a clear policy mandate; established networks of collaborators; iterative co-design of a user-friendly interface; standardized, comprehensive and documented methods with quality assurance; consistent capacity and succession planning; accessible data and value-added products that are fit-for-purpose; and metrics of use collated and reported. The outcomes of this review are intended to: (a) support data creators/owners/providers in designing and curating biodiversity and conservation knowledge products that have greater influence, and hence impact, in policy- and decision-making, and (b) provide recommendations for how decision- and policy-makers can support the development, implementation, and sustainability of robust biodiversity and conservation knowledge products through the framing of marine policy and decision-making frameworks.

Description: (19.06. – 25.06.2017)

Description: Nitrogen (N) is the major limiting nutrient for phytoplankton growth and productivity in large parts of the world's oceans. Differential preferences for specific N substrates may be important in controlling phytoplankton community composition. To date, there is limited information on how specific N substrates influence the composition of naturally occurring microbial communities. We investigated the effect of nitrate ( math formula), ammonium ( math formula), and urea on microbial and phytoplankton community composition (cell abundances and 16S rRNA gene profiling) and functioning (photosynthetic activity, carbon fixation rates) in the oligotrophic waters of the North Pacific Ocean. All N substrates tested significantly stimulated phytoplankton growth and productivity. Urea resulted in the greatest (〉300%) increases in chlorophyll a (〈0.06 μg L−1 and ∼0.19 μg L−1 in the control and urea addition, respectively) and productivity (〈0.4 μmol C L−1 d−1 and ∼1.4 μmol C L−1 d−1 in the control and urea addition, respectively) at two experimental stations, largely due to increased abundances of Prochlorococcus (Cyanobacteria). Two abundant clades of Prochlorococcus, High Light I and II, demonstrated similar responses to urea, suggesting this substrate is likely an important N source for natural Prochlorococcus populations. In contrast, the heterotrophic community composition changed most in response to math formula. Finally, the time and magnitude of response to N amendments varied with geographic location, likely due to differences in microbial community composition and their nutrient status. Our results provide support for the hypothesis that changes in N supply would likely favor specific populations of phytoplankton in different oceanic regions and thus, affect both biogeochemical cycles and ecological processes.

Description: Highlights • Chronometric dating of Neanderthal remains to 190 ka from the volcanic context of Wannen-Ochtendung. • Red thermoluminescence dating (RTL) of heated detritical quartz extracted from crustal xenoliths • Shortened and full single aliquot regeneration (SAR) protocols agree. • Perfect agreement of RTL dating with argon dating for the identical events Abstract The partial neurocranium of a Neanderthal was recovered from deposits related to the latest volcanic activities recorded at the Wannen Volcanic Group. This last volcanic event provided heated mineral samples for thermoluminescence (TL) and Ar/Ar dating, allowing the estimation of the age of the hominin remains. Novel TL methods using a much less time consuming measurement protocol and employing the orange-red TL-signal (R-TL) were applied, resulting in ages of 177 ± 18 ka and 176 ± 21 ka for two samples of different geology. This new data is compared with standard TL-approaches for one of the samples, which provide an age of 187 ± 29 ka. The luminescence data is contrasted with a newly obtained Ar/Ar-age of 191 ± 12 ka for a sample from the identical heating event. All TL-dating results provide congruent results and are in perfect accordance with Ar/Ar dating, showing the applicability and accuracy of the new TL approach employed. These data also agree well with the geological age estimates and other chronometric data, placing the volcanism at Wannen to around 180–190 ka and thus providing a Saalian age of the fossil. Such an old age, however, contrasts to the reported preliminary placement of this specimen late in the Neanderthal lineage.

Description: FS METEOR Reise M138, Callao (Peru) - Cristobal (Panama)

Description: (15/05/17 to 21/05/17)

Description: The expanding interest in decadal climate variability, predictability, and prediction highlights the importance of understanding the sources and mechanisms of decadal and interdecadal climate fluctuations. The purpose of this paper is to provide a critical review of our current understanding of externally forced decadal climate variability. In particular, proposed mechanisms determining decadal climate responses to variations in solar activity, stratospheric volcanic aerosols, and natural as well as anthropogenic tropospheric aerosols are discussed, both separately and in a unified framework. The review suggests that the excitation of internal modes of interdecadal climate variability, particularly centered in the Pacific and North Atlantic sectors, remains a paradigm to characterize externally forced decadal climate variability and to interpret the associated dynamics. Significant recent advancements are the improved understanding of the critical dependency of volcanically forced decadal climate variability on the relative phase of ongoing internal variability and on additional external perturbations, and the recognition that associated uncertainty may represent a serious obstacle to identifying the climatic consequences even of very strong eruptions. Particularly relevant is also the recent development of hypotheses about potential mechanisms (reemergence and synchronization) underlying solar forced decadal climate variability. Finally, outstanding issues and, hence, major opportunities for progress regarding externally forced decadal climate variability are discussed. Uncertain characterization of forcing and climate histories, imperfect implementation of complex forcings in climate models, limited understanding of the internal component of interdecadal climate variability, and poor quality of its simulation are some of the enduring critical obstacles on which to progress. It is suggested that much further understanding can be gained through identification and investigation of relevant periods of forced decadal climate variability during the preindustrial past millennium. Another upcoming opportunity for progress is the analysis of focused experiments with coupled ocean–atmosphere general circulation models within the umbrella of the next phase of the coupled model intercomparison project.

Description: (22/05/17 to 24/05/17)

Description: We examine the mean pathways, transit timescales, and transformation of waters flowing from the Pacific and the marginal seas through the Indian Ocean (IO) on their way toward the South Atlantic within a high-resolution ocean/sea-ice model. The model fields are analyzed from a Lagrangian perspective where water volumes are tracked as they enter the IO. The IO contributes 12.6 Sv to Agulhas leakage, which within the model is 14.1 ± 2.2 Sv, the rest originates from the South Atlantic. The Indonesian Through-flow constitutes about half of the IO contribution, is surface bound, cools and salinificates as it leaves the basin within 10–30 years. Waters entering the IO south of Australia are at intermediate depths and maintain their temperature-salinity properties as they exit the basin within 15–35 years. Of these waters, the contribution from Tasman leakage is 1.4 Sv. The rest stem from recirculation from the frontal regions of the Southern Ocean. The marginal seas export 1.0 Sv into the Atlantic within 15–40 years, and the waters cool and freshen on-route. However, the model's simulation of waters from the Gulfs of Aden and Oman are too light and hence overly influenced by upper ocean circulations. In the Cape Basin, Agulhas leakage is well mixed. On-route, temperature-salinity transformations occur predominantly in the Arabian Sea and within the greater Agulhas Current region. Overall, the IO exports at least 7.9 Sv from the Pacific to the Atlantic, thereby quantifying the strength of the upper cell of the global conveyor belt.

Description: This study applies three classification methods exploiting the angular dependence of acoustic seafloor backscatter along with high resolution sub-bottom profiling for seafloor sediment characterization in the Eckernförde Bay, Baltic Sea Germany. This area is well suited for acoustic backscatter studies due to its shallowness, its smooth bathymetry and the presence of a wide range of sediment types. Backscatter data were acquired using a Seabeam1180 (180 kHz) multibeam echosounder and sub-bottom profiler data were recorded using a SES-2000 parametric sonar transmitting 6 and 12 kHz. The high density of seafloor soundings allowed extracting backscatter layers for five beam angles over a large part of the surveyed area. A Bayesian probability method was employed for sediment classification based on the backscatter variability at a single incidence angle, whereas Maximum Likelihood Classification (MLC) and Principal Components Analysis (PCA) were applied to the multi-angle layers. The Bayesian approach was used for identifying the optimum number of acoustic classes because cluster validation is carried out prior to class assignment and class outputs are ordinal categorical values. The method is based on the principle that backscatter values from a single incidence angle express a normal distribution for a particular sediment type. The resulting Bayesian classes were well correlated to median grain sizes and the percentage of coarse material. The MLC method uses angular response information from five layers of training areas extracted from the Bayesian classification map. The subsequent PCA analysis is based on the transformation of these five layers into two principal components that comprise most of the data variability. These principal components were clustered in five classes after running an external cluster validation test. In general both methods MLC and PCA, separated the various sediment types effectively, showing good agreement (kappa 〉0.7) with the Bayesian approach which also correlates well with ground truth data (r2 〉 0.7). In addition, sub-bottom data were used in conjunction with the Bayesian classification results to characterize acoustic classes with respect to their geological and stratigraphic interpretation. The joined interpretation of seafloor and sub-seafloor data sets proved to be an efficient approach for a better understanding of seafloor backscatter patchiness and to discriminate acoustically similar classes in different geological/bathymetric settings.

Description: The transition from benthos to plankton requires multiple adaptations, yet so far it remains unclear how these are acquired in the course of the transition. To investigate this process, we analyzed the genetic diversity and distribution patterns of a group of foraminifera of the genus Bolivina with a tychopelagic mode of life (same species occurring both in benthos and plankton). We assembled a global sequence data set for this group from single-cell DNA extractions and occurrences in metabarcodes from pelagic environmental samples. The pelagic sequences all cluster within a single monophyletic clade within Bolivina. This clade harbors three distinct genetic lineages, which are associated with incipient morphological differentiation. All lineages occur in the plankton and benthos, but only one lineage exhibits no limit to offshore dispersal and has been shown to grow in the plankton. These observations indicate that the emergence of buoyancy regulation within the clade preceded the evolution of pelagic feeding and that the evolution of both traits was not channeled into a full transition into the plankton. We infer that in foraminifera, colonization of the planktonic niche may occur by sequential cooptation of independently acquired traits, with holoplanktonic species being recruited from tychopelagic ancestors

Description: Seafloor deformation is intrinsically related to tectonic processes, which potentially may evolve into geohazards, including earthquakes and tsunamis. The nascent scientific field of seafloor geodesy provides a way to monitor crustal deformation at high resolution comparable to the satellite-based GPS technique upon which terrestrial geodesy is largely based. The measurements extract information on stress and elastic strain stored in the oceanic crust. Horizontal seafloor displacement can be obtained by acoustic/GPS combination to provide absolute positioning or by long-term acoustic telemetry between different beacons fixed on the seafloor. The GeoSEA (Geodetic Earthquake Observatory on the SEAfloor) array uses acoustic telemetry for relative positioning at mm-scale resolution. The transponders within an array intercommunicate via acoustic signals for a period of up to 3.5 years. The seafloor acoustic transponders are mounted on ∼4 m high tripod steel frames to ensure clear line-of-sight between the stations. The transponders also include high-precision pressure sensors to monitor vertical movements and dual-axis inclinometers in order to measure their level as well as any tilt of the seafloor. Sound velocity sensor measurements are used to correct for water sound speed variations. A further component of the network is GeoSURF, a self-steering autonomous surface vehicle (Wave Glider), which monitors system health and is able to upload the seafloor data to the sea surface and to transfer it via satellite. The GeoSEA array is capable of both continuously monitoring horizontal and vertical ground displacement rates along submarine fault zones and characterizing their behavior (locked or aseismically creeping). Seafloor transponders are currently installed along the Siliviri segment of the North Anatolian Fault offshore Istanbul for measurements of strain build-up along the fault. The first 18 month of baseline ranging were analyzed by a joint-least square inversion and forward modeling for across-fault baseline changes. The initial results of the long-term observation period preclude fault-displacement at rates larger than a few millimeters-per-year, suggesting a locked state for the Istanbul-Siliviri segment, indicating that this portion of the fault is accumulating stress rather than continuously creeping at a slip-rate higher than 10 mm/yr during the observation period. In addition, three arrays are currently deployed on the marine forearc and outer rise of the South American subduction system around 21◦S. This segment of the Nazca-South American plate boundary has last ruptured in an earthquake in 1877 and was identified as a seismic gap prior to the 2014 Iquique/Pisagua earthquake (Mw=8.1). The southern portion of the segment remains unbroken by a recent earthquake.

Description: Fütterungsversuche mit Regenbogenforellen zeigen: Magen-Darm-Bakterien von Raubfischen passen sich an vegetarische Nahrung an

Description: Highlights: • We investigated growth and longevity of three deep-sea squids from the Monterey Bay. • We found daily growth increments in the statoliths of two deep-sea squids. • The estimated longevities are higher than those of shallow water relatives. • The estimated growth rates suggest a reduced pace of life in deep-sea squids. Abstract Coastal and epipelagic cephalopods are among the fastest growing invertebrates, with life cycles of typically 1 year or less. Evidence is accumulating that deep-sea taxa often live longer and grow slower than their shallow water relatives. We test the hypothesis that deep-sea squid show increased longevity and reduced growth rates compared to coastal and epipelagic species, by validation experiments and quantification of statolith increments of three deep-sea squids from the Monterey Submarine Canyon. The periodicity of statolith increment formation in coastal species is daily, but is unknown for deep-sea squid. Between 2010 and 2013, specimens of Chiroteuthis calyx, Galiteuthis phyllura and Octopoteuthis deletron were captured by remotely operated vehicles and trawl nets off California. ROV-captured living squid were immersed in tetracycline and kept alive in the lab for between 3 and 14 days. Correlating the number of elapsed days with the number of newly deposited statolith increments, and statolith growth after the fluorescent tetracycline mark, provided evidence of regular and daily increment deposition, in C. calyx and O. deletron. This relationship was less strong in G. phyllura and the one-increment-per-day hypothesis was not accepted for this species. Reconstructing growth rates based on statolith counts and wet weights from animals of a wide size range suggest that O. deletron is a slower growing squid (0.59% BW/day) than C. calyx (1.3% BW/day) and G. phyllura (1.2% BW/day). Octopoteuthis deletron matures at around two years, the oldest C. calyx was a mature male of 1.5 years and the eldest G. phyllura was 10 months and still immature. Maximum reported sizes for G. phyllura and C. calyx exceed those of our examined specimens, and therefore their longevity likely exceeds 2 years, in particular if the females brood their eggs. Our study supports the hypothesis that deeper living squid exhibit reduced growth rates and an increased longevity compared to shallow living species. We discuss these traits in the context of a life in the deep pelagic ocean.

Description: POS515 CALVADOS - CALabrian arc mud VolcAnoes: Deep Origin and internal Structure, June 18 – July 13, 2017, Dubrovnik - Catania

Description: Wochenbericht AL – 496, 01.07. – 12.07.2017

Description: Highlights • Identify new fine-grained hydrate filled fracture units in the Terrebonne Basin. • Identify new hydrate bearing thin sands, mostly within fractured muds. • Present detailed seismic amplitude maps of the new hydrate bearing units. • Discuss methane migration mechanisms and hydrate formation in thin sands. • Identify and discuss source-reservoir relationships between thick muds and thin sands. Abstract The interactions of microbial methane generation in fine-grained clay-rich sediments, methane migration, and gas hydrate accumulation in coarse-grained, sand-rich sediments are not yet fully understood. The Terrebonne Basin in the northern Gulf of Mexico provides an ideal setting to investigate the migration of methane resulting in the formation of hydrate in thin sand units interbedded with fractured muds. Using 3D seismic and well log data, we have identified several previously unidentified hydrate bearing units in the Terrebonne Basin. Two units are 〉100 m-thick fine-grained clay-rich units where gas hydrate occurs in near-vertical fractures. In some locations, these fine-grained units lack fracture features, and they contain 1–4-m thick hydrate bearing-sands. In addition, several other thin sand units were identified that contain gas hydrate, including one sand that was intersected by a well at the location of a discontinuous bottom-simulating reflector. Using correlation of well log data to seismic data, we have mapped and described these new units in detail across the extent of the available data, allowing us to determine the variation of seismic amplitudes and investigate the distribution of free gas and/or hydrate. We present several potential source-reservoir scenarios between the thick fractured mud units and thin hydrate bearing sands. We observe that hydrate preferentially forms within thin sand layers rather than fractures when sands are present in larger marine mud units. Based on regional mapping showing the patchy lateral extent of the thin sand layers, we propose that diffusive methane migration or short-migration of microbially generated methane from the marine mud units led to the formation of hydrate in these thin sands, as discontinuous sands would not be conducive to long-range migration of methane from deeper reservoirs.

Description: Over the last decade there has been renewed interest in determining the water contents of basaltic magmas. A commonly applied method is analysis of H2O from melt inclusions in olivine. However, it is also well known that these can rapidly lose (or gain) H2O by diffusion. An alternative is to measure the H2O contents of clinopyroxene phenocrysts and use a partition coefficient (D) to estimate the original H2O content of the host magma. This approach is not without complications and several recent studies have attempted to assess the effects of diffusive loss of H2O from magmatic clinopyroxenes. In the ideal case, these crystals should be taken from rapidly cooled tephra or lapilli but such materials are not always available. In order to further assess the potential of using 5-10mm clinopyroxenes from lavas we undertook a detailed, multi-analytical investigation of clinopyroxenes from an ankaramite flow on Pico Island in the Azores. We conclude that these can be trusted to preserve (probably minimum) magmatic H2O contents if the H2O concentrations of multiple clinopyroxenes from a single sample form a linear correlation with the AlIV content that demonstrates a coupled substitution with little or no H2O loss. Conversely, if H2O contents decrease from core to rim whereas AlIV contents remain relatively constant then it is likely that those clinopyroxenes lost H2O during differentiation and/or cooling. We suspect that the olivine melt inclusions we analysed from Pico and São Miguel Islands also underwent diffusive loss of H2O. Using these criteria, we present clinopyroxene-derived magmatic H2O estimates for Corvo, Flores Faial, Pico and São Miguel Islands that range from 0.28 to 2.2wt%. When combined with published data these show that H2O contents often extend to higher values on the islands than along the adjacent mid-Atlantic ridge. These localised, elevated H2O contents can explain why the islands are emergent despite being situated away from the ridge and perhaps also the asymmetric nature of the bathymetry of the archipelago. It is possible that this H2O was recycled from material subducted very early on in Earth's history.

Description: Vulkane faszinieren uns Menschen schon immer durch ihre spektakulären Ausbrüche. Ungleich bedeutender waren seit jeher die fruchtbaren vulkanischen Böden, gewaltigen Vorräte an Erdwärme und große Schönheit der Vulkane. Die Vulkanexperten Hans-Ulrich Schmincke und Mari Sumita haben in diesem Buch ihr Wissen zusammengefasst, das sie durch Arbeiten auf allen Kontinenten erwarben. Sie erklären auch, mit welchen Methoden Vulkanausbrüche heutzutage erfolgreich vorhergesagt werden können.

Description: One of the major challenges in ecological stoichiometry is to establish how environmental changes in resource availability may affect both the biochemical composition of organisms and the species composition of communities. This is a pressing issue in many coastal waters, where anthropogenic activities have caused large changes in riverine nutrient inputs. Here we investigate variation in the biochemical composition and synthesis of amino acids, fatty acids (FA), and carbohydrates in mixed phytoplankton communities sampled from the North Sea. The communities were cultured in chemostats supplied with different concentrations of dissolved inorganic nitrogen (DIN) and phosphorus (DIP) to establish four different types of resource limitations. Diatoms dominated under N-limited, N+P limited and P-limited conditions. Cyanobacteria became dominant in one of the N-limited chemostats and green algae dominated in the one P-limited chemostat and under light-limited conditions. Changes in nutrient availability directly affected amino acid content, which was lowest under N and N+P limitation, higher under P-limitation and highest when light was the limiting factor. Storage carbohydrate content showed the opposite trend and storage FA content seemed to be co-dependent on community composition. The synthesis of essential amino acids was affected under N and N+P limitation, as the transformation from non-essential to essential amino acids decreased at DIN:DIP ≤ 6. The simple community structure and clearly identifiable nutrient limitations confirm and clarify previous field findings in the North Sea. Our results show that different phytoplankton groups are capable of adapting their key biosynthetic rates and hence their biochemical composition to different degrees when experiencing shifts in nutrient availability. This will have implications for phytoplankton growth, community structure, and the nutritional quality of phytoplankton as food for higher trophic levels.