ALBERT

Description: The vast majority of active volcanism that is located at plate boundaries can be easily explained by plate tectonic processes. Intraplate volcanism, which incorporates some of the smallest and largest volcanic events on Earth, cannot be successfully explained by a single process or model. The most volumetrically significant intraplate volcanic events are associated with the arrival of the head of a thermo-chemical anomaly rising from the deep mantle and impacting the base of the lithosphere. This event generates massive and short-lived magmatic activity over a wide area (up to 2000 km across), forming a large igneous province. A long-lived hotspot track can form over the mantle plume tail and is best illustrated by the formation of age progressive volcanic chains, such as the famous Hawaiian-Emperor chain. Millions of smaller solitary volcanic edifices, non-age progressive volcanic chains and provinces, on the other hand, have other potential mechanisms of origin. Potential models comprise decompression melting due to lithospheric extension, destabilization of fusible lithologies in the lithospheric mantle, small scale sub-lithospheric convection, or lithospheric delamination.

Description: Gas hydrates dissociation could induce or trigger submarine landslides, especially in upper continental slopes where hydrates are vulnerable to natural and artificial perturbations. This work investigates destabilization mechanisms of an upper continental slope undergoing hydrate dissociation and identifies spatiotemporal failure modes influenced by characteristics of the overburden above the hydrate-bearing layer (i.e. the hydrate reservoir). A Thermo-Hydro-Chemical coupled numerical model of transient pore pressure induced by hydrate dissociation is coupled with the limit equilibrium slope analysis method to study the spatiotemporal evolution of the potential sliding plane and to calculate the corresponding factor of safety. The results suggest that overpressure generated by the liberated fluid from hydrate dissociation is the primary reason for instability in a gentle marine slope. The study identifies three sliding modes, namely co-melting non-interface sliding, co-melting interface sliding, and post-melting non-interface sliding, depending on the overburden's characteristics, including overburden thickness, permeability, and cohesion. Co-melting non-interface sliding takes place during hydrate dissociation if the hydrate reservoir underlies a thin, pervious and low-cohesion overburden cover. For less permeable and more cohesive overburdens, the potential sliding plane is deeper and co-melting interface sliding could be triggered due to overpressure developed at the reservoir-overburden interface. If the hydrate reservoir is covered by a thick, low-permeability and slightly cohesive overburden, post-melting non-interface sliding could occur after the hydrates are completely dissociated. This failure is delayed, because the gas/water trapped at the interface during hydrate dissociation is insufficient to trigger instability due to very high overburden stresses. However, as the gas migrates upwards over time and encounters a weak zone in the overburden deposits, failure could happen within the overburden deposits even after hydrate dissociation stops. The findings help to improve our fundamental understanding about the destabilization mechanism and failure modes of the continental slopes undergoing hydrate dissociation, and to delineate the vulnerable configurations of the slopes.

Description: n our daily lives, we consume foods that have been transported, stored, prepared, cooked, or otherwise processed by ourselves or others. Food storage and preparation have drastic effects on the chemical composition of foods. Untargeted mass spectrometry analysis of food samples has the potential to increase our chemical understanding of these processes by detecting a broad spectrum of chemicals. We performed a time-based analysis of the chemical changes in foods during common preparations, such as fermentation, brewing, and ripening, using untargeted mass spectrometry and molecular networking. The data analysis workflow presented implements an approach to study changes in food chemistry that can reveal global alterations in chemical profiles, identify changes in abundance, as well as identify specific chemicals and their transformation products. The data generated in this study are publicly available, enabling the replication and re-analysis of these data in isolation, and serve as a baseline dataset for future investigations.

Description: A comparison of gouge and hammer coring techniques in intertidal wetland soils highlights a significant effect of soil compaction of up to 28% associated with the widely applied hammer coring method employed in Blue Carbon research. Hammer coring reduces the thickness of the soil profile and increases the dry bulk density, which results in an overestimation of the soil OC stock of up to 22%. In saltmarshes with multiple different soil units, we show that hammer coring is unsuitable for the calculation of OC stocks and should be avoided in favour of Russian or gouge cores. Compaction changes both soil dry bulk density and porosity and we show that resultant radiometric chronologies are compromised, almost doubling mass accumulation rates. While we show that the OC (%) content of these sediments is largely unchanged by coring method, the implication for OC burial rates are profound because of the significant effect of hammer coring on the calculation of soil mass accumlation rates.

Description: Seagrasses provide multiple ‘ecosystem services' in coastal waters, including carbon sequestration. However, this ‘Blue Carbon’ potential has been only evaluated for certain species from some areas of the world. In this study, we provide initial estimates on the magnitude and local variability of carbon sequestration, as organic carbon stocks, for seagrass meadows of Cymodocea nodosa (Ucria) Ascherson in the oceanic island of Gran Canaria (Canary Islands, Spain, central-eastern Atlantic). Six seagrass meadows were selected; at each meadow, cores inserted up to 30 cm in the seabed were collected in the ‘interior’, ‘edge’ and ‘unvegetated’ bottoms immediately adjacent to seagrass patches. We estimated organic carbon (Corg) pools by means of the Loss of Ignition (LOI) procedure. Overall, larger Corg pools were observed in the ‘interior’ and 'edges' of meadow patches than in adjacent ‘unvegetated’ bottoms. At the meadow-level, Corg pools were not predicted neither by the meadow area, nor by the mean shoot density, or sediment grain fractions. Overall, the total estimated stock was 86.20 ± 19.06 Mg C ha−1. By considering the total potential extension of seagrass meadows across the entire island perimeter, we estimated a total stock of 60.34 Gg of C, for a mean estimated financial value of 919,432.249 € (1313.47 € ha−1), which ranges between 351,631.35 € (502.33 € ha−1) and 1,498,954.45 € (2141.36 € ha−1), according to varying market prices in the last 5 years. This work highlights, therefore, the importance of meadows underpinned by C. nodosa not only at an ecological, but also at an economic level, in particular from the perspective of regional climate change adaptation strategies.

Description: Ciona intestinalis is within the group of taxa that are spreading globally and is one of the most thriving invasive marine species, known to depress both species richness and abundance at a local scale in distinct geographic areas. It is a dominant biofouling agent, associated with the decreasing economic incomes from aquaculture operations around the world. Ciona intestinalis was first observed in 2007 at Straumsvík in Southwest Iceland. The present study was designed to provide general information on its current distribution across Icelandic harbours. The species was found only on the SW coast of Iceland, in dense aggregations reaching up to 876 ind/m2 in all harbours from Grindavík to Akranes. The current work provides information that can be used to track the dispersal of C. intestinalis populations along the Icelandic coast and for the development of effective management decisions.

Description: Interest in microalgae-derived products is growing, mostly due to their unique characteristics and range of industrial applications. To obtain different products, one must employ specific pretreatments that retain the properties of the biologically active compounds extracted from microalgae biomass; thus, new extraction techniques require frequent upgrades. Due to increased interest in economically viable and ecologically friendly processes, new extraction methods that can be incorporated into microalgae biorefinery systems have become the main focus of research. Therefore, this review aims to address the potential applications, future prospects, and economic scenario of the new physicochemical treatments used in the extraction of bioactive microalgae compounds.

Description: Long-chain polyunsaturated fatty acids (LC-PUFAs) especially ω-3 fatty acids provide significant health benefits for human beings. However, ω-3 LC-PUFAs cannot be synthesized de novo in mammals. Traditionally, ω-3 LC-PUFAs are extracted from marine fish, and their production depends on sea fishing, which has not met ever-increasing global demand. To address the challenges, innovative cellular engineering strategies need to be developed. In nature, many fungi and microalgae are rich in ω-3 LC-PUFAs, representing promising sources of ω-3 LC-PUFAs. The latest progress in developing new cellular engineering strategies toward sustainable ω-3 LC-PUFAs production using fungi and microalga has demonstrated that they can to some extent address the supply shortage. In this review, we critically summarize the recent progress in enhancing the productivity in various ω-3 LC-PUFAs-producing organisms, as well as the latest efforts of biosynthesizing PUFAs in heterogenous biosystems. In addition, we also provide future perspectives in developing genetic toolkits for LC-PUFAs producing microbes so that cut-edging biotechnology such as gene stacking and genome editing can be further applied to increase the productivity of ω-3 LC-PUFAs.

Description: Factors affecting carotenoid extraction with edible oils were examined using edible brown seaweed, Sargassum horneri, as main sample. The results indicate that drying was essential to extract fucoxanthin (Fx) from S. horneri and physical (boiling) and chemical (acid/alkali) pretreatment of the wet sample increased the extraction rate of Fx. Additionally, more Fx was found from the dried S. horneri powder with a smaller particle size. The extraction rate of Fx is affected by the extraction temperature and time, showing that the effective extraction would be obtained at 50 °C within 12 hr extraction. Among the oils used, short-chain (C4 and C6) triacylglycerol (TAG) (SCT) and medium-chain (C8) TAG (MCT) could extract more Fx from S. horneri and more β-carotene and lutein from spinach and olive leaves. The relatively lower viscosity of SCT and MCT would be the most likely reason for the higher extraction rates of both TAGs.

Description: Sargassum fusiforme polysaccharides, acidic water-soluble polysaccharides extract from Sargassum fusiforme, are mainly composed of alginic acid, fucoidan and laminaran. Alginic acid is carboxyl-containing polysaccharide formed by joining β-D-mannuronic acid and α-L-guluronic acid through β-(1→4)/α-(1→4) glycosidic bond. Fucoidan, a natural water-soluble sulfated heteropolysaccharide with fucose and sulfuric acid groups as the core structure, is mainly linked by L-fucose through α-(1→3) glycosidic bond and has the strongest biological activity. Laminaran is mainly composed of β-D-glucose through β-(1→3) glycosidic bond linkage. Sargassum fusiforme polysaccharides have a variety of pharmacological activities, including antioxidant, anti-tumor, promoting immunity, anti-aging, prompting bone growth, lowering blood glucose, anti-coagulation, anti-virus, anti-bacteria, anti-fatigue, promoting growth and development, and skin protection. These activities are closely related to the functions of fucoidan in Sargassum fusiforme polysaccharides, which fucoidan is able to strengthen immune system and antioxidation in human body. In this review, the composition, the isolation and purification, and the biological activities of Sargassum fusiforme polysaccharides are discussed and can bereference for further study.

Description: Numerical simulation is important for practical and efficient assessment of hydrate reservoir formation stability and gas production potential. The history-matching simulation of hydrate gas production tests is complex due to coupled THM (thermo-hydro-mechanical) phenomena. The well log data from the Eastern Nankai Trough methane gas production site suggest vertically heterogeneous field properties. In the previous numerical simulation research of this site, the heterogeneous geological data were homogenized by adopting the standard mean-field theory, which can potentially lead to inaccurate simulation results due to the mesh size effect. By introducing new upscaling techniques for the permeability profiles and mechanical responses, a revised homogenization approach is proposed to improve the coupled THM simulation accuracy. In this study, seven gas production simulations of a hypothetical reservoir, six simulations of the Eastern Nankai Trough gas production test, and four simulations of the randomly generated site formation production test with different mesh sizes and different homogenization approaches were carried out to demonstrate that the proposed upscaling techniques can improve the accuracy of the simulation results with a coarse mesh model. This work, in turn, provides researchers and field engineers a much quicker way to assess the complex geomechanical behaviors of hydrate gas production site.

Description: Nitrous oxide is an important greenhouse gas and there is a need for sensitive techniques to study its distribution in the environment at concentrations near equilibrium with the atmosphere (9.6 nM in water at 20 °C). Here we present an electrochemical sensor that can quantify N2O in the nanomolar range. The sensor principle relies on a front guard cathode placed in front of the measuring cathode. This cathode is used to periodically block the flux of N2O towards the measuring cathode, thereby creating an amplitude in the signal. This signal amplitude is unaffected by drift in the baseline current and can be read at very high resolution, resulting in a sensitivity of 2 nM N2O for newly constructed sensors. Interference from oxygen is prevented by placing the front guard cathode in oxygen-consuming electrolyte. The sensor was field tested by measuring an N2O profile to a depth of 120 m in the oxygen minimum zone of the Eastern Tropical North Pacific Ocean (ETNP) off the coast of Mexico.

Description: The ability of consumers to convert ingested carbon into growth is critical for secondary production and trophic transfer. We conducted laboratory experiments to investigate the effect of different prey and concentration on the ingestion rate (IR), egg production rate (EPR) and egg production efficiency (EPE) of the ubiquitous copepod, Acartia tonsa. Experiments were run at several prey concentrations, ranging from 11 to 1132 μgC L–1, of the diatom Thalassiosira weissflogii, the autotrophic dinoflagellate Prorocentrum minimum, the heterotrophic dinoflagellate Oxyrrhis sp., the flagellate Dunaliella tertiolecta, and the bacterivorous scuticociliate Uronema sp. IR increased curvilinearly with concentration for all diets. EPR also increased curvilinearly with increasing food concentration similar to IR, with the exception of the flagellate diet, for which EPR decreased linearly with food concentration. EPR ranked as T. weissflogii 〉 P. minimum 〉 Oxyrrhis sp. = Uronema sp. 〉 D. tertiolecta. IR and EPR were linearly related, except for flagellate diet. The slope of the carbon-based relationship between IR and EPR, the egg production efficiency (EPE), was highest for the diatom (77.5%) and lowest for the scuticociliate (4.2%). Egg production was not correlated to ingestion of the flagellate offered to A. tonsa. We conclude that of the five prey species, the diatom T. weissflogii is the best prey to promote A. tonsa reproduction, to optimize trophic transfer efficiency, and to increase mass cultivation of this species.

Description: Geochemical patterns in the environment are always the result of certain processes. Therefore, it is essential to decipher a process to properly evaluate the environmental role and potential of chemical elements/compounds. This allows the distinction between natural and anthropogenic influence on elemental concentrations. However, if the compositional nature of geochemical data is neglected, erroneous or misleading conclusions regarding the processes involved are probable. In this study the reconstruction of depositional environments and processes through the Holocene in two sediment cores obtained from submerged sinkholes located on the island of Mljet, Croatia, was performed by taking into account the compositional nature of geochemical, mineralogical and grainsize data. Problems involving compositional data are always multivariate; for example, the concentration of a single element does not carry any interpretative information, as only the ratios between elements do. This has led to the discovery of a large number of geochemical proxies based on elemental ratios, which describe certain environmental conditions and processes involved. Nevertheless, some proxies have been found to be restricted to only some specific environments, thus preventing them from being used in general; therefore, some kind of relation between different proxies is necessary to obtain final conclusions. However, when using simple elemental ratios, those correlations cannot be obtained due to the nature of compositional data. With a sequential binary partition of a compositional vector, orthonormal log ratio (olr) coordinates (proxies) can be constructed. When based on expert knowledge, those proxies fully acknowledge the geochemical properties of the chosen elements with one major difference - that the correlation between newly obtained variables is mathematically well grounded. As a result, the final conclusion is more accurate. In this research, geochemical proxies obtained as a representation in olr coordinates of the elements that are enriched compared to the local soil were used to perform principal component analyses. It helped to unravel the evolution of sedimentary environments. Mineralogical (XRD and heavy mineral data) and grain size analyses supported the conclusions obtained based solely on geochemical data. Furthermore, data analysis suggests that the proxies for redox conditions described in the literature should be used with caution, as their use is somewhat limited.

Description: New antifungals are increasingly needed due to the emergence of resistant fungal strains. Traditional antifungal assays are laborious and require significant amounts of samples. The present work presents a new proposal to evaluate antifungal activity and antagonism among fungal species, based on experiments of fungal culture and co-culture, 1H NMR profile of fungal culture extracts and chemometrics. In order to develop the work, six axenic cultures of fungi that infested fruits (Fusarium guttiforme, Pestalotiopsis diospyri, Phoma caricae-papayae, Colletotrichum horii, Phytophthora palmivora, and C. gloeosporioides), and co-cultures of all possible combination among them were performed (totalizing 63 experiments). All fungal extracts were evaluated by 1H NMR followed by Principal Component Analyses (PCA) in order to determine spectral dissimilarity among the extracts. Results showed that 1H NMR data evaluated by PCA were capable to predict both antagonism and antifungal activity. Traditional antifungal in vitro assays of active and inactive extracts were also performed in order to prove the prediction made by PCA. The obtained data showed that the approach is an outstanding tool to simultaneously obtain and evaluate bioactive compounds because: it was able to predict the activity of five different extracts in a collection of sixty-three, which would be much more difficult and time consuming if applied randomly; most important antifungal extracts are indicated by PCA; hundreds of traditional in vitro assays are avoid; and, the method is very time and money saving.

Description: Highlights • Total modeled carbon cycling at disturbed sites is lower than at reference sites. • Projected microbial loop functioning is reduced 26 years after sediment disturbance. • Estimated faunal respiration has recovered from sediment disturbance. • Estimated microbial respiration has not recovered from the sediment disturbance. Abstract Due to the predicted future demand for critical metals, abyssal plains covered with polymetallic nodules are currently being prospected for deep-seabed mining. Deep-seabed mining will lead to significant sediment disturbance over large spatial scales and for extended periods of time. The environmental impact of a small-scale sediment disturbance was studied during the ‘DISturbance and reCOLonization’ (DISCOL) experiment in the Peru Basin in 1989 when 10.8 km2 of seafloor were ploughed with a plough harrow. Here, we present a detailed description of carbon-based food-web models constructed from various datasets collected in 2015, 26 years after the experiment. Detailed observations of the benthic food web were made at three distinct sites: inside 26-year old plough tracks (IPT, subjected to direct impact from ploughing), outside the plough tracks (OPT, exposed to settling of resuspended sediment), and at reference sites (REF, no impact). The observations were used to develop highly-resolved food-web models for each site that quantified the carbon (C) fluxes between biotic (ranging from prokaryotes to various functional groups in meio-, macro-, and megafauna) and abiotic (e.g. detritus) compartments. The model outputs were used to estimate total system throughput, i.e., the sum of all C flows in the food web (the ‘ecological size’ of the system), and microbial loop functioning, i.e., the C-cycling through the prokaryotic compartment for each site. Both the estimated total system throughput and the microbial loop cycling were significantly reduced (by 16% and 35%, respectively) inside the plough tracks compared to the other two sites. Site differences in modelled faunal respiration varied among the different faunal compartments. Overall, modelled faunal respiration appeared to have recovered to, or exceeded reference values after 26-years. The model results indicate that food-web functioning, and especially the microbial loop, have not recovered from the disturbance that was inflicted on the abyssal site 26 years ago.

Description: Highlights: • Crystal structure of the malaria parasite lipocalin • Comparative analysis of lipocalin superfamily members in alveolate genomes • Localization of PfLipocalin to the parasitophorous vacuole and food vacuole • Reverse genetics reveal PfLipocalin function in oxidative damage control Summary: Proteins of the lipocalin family are known to bind small hydrophobic ligands and are involved in various physiological processes ranging from lipid transport to oxidative stress responses. The genome of the malaria parasite Plasmodium falciparum contains a single protein PF3D7_0925900 with a lipocalin signature. Using crystallography and small-angle X-ray scattering, we show that the protein has a tetrameric structure of typical lipocalin monomers; hence we name it P. falciparum lipocalin (PfLCN). We show that PfLCN is expressed in the intraerythrocytic stages of the parasite and localizes to the parasitophorous and food vacuoles. Conditional knockdown of PfLCN impairs parasite development, which can be rescued by treatment with the radical scavenger Trolox or by temporal inhibition of hemoglobin digestion. This suggests a key function of PfLCN in counteracting oxidative stress-induced cell damage during multiplication of parasites within erythrocytes.

Description: Eco-friendly, cost efficient and effective extraction methods have become significant for the industries applying zero waste principles. The two main objectives of this study were; to examine fucoxanthin extraction from wet Phaeodactylum tricornutum using subcritical fluid extraction and to characterize the residual biomass in order to determine the potential application areas. The highest fucoxanthin yield of 0.69 ± 0.05 mg/g wet cell weight was achieved using methanol with solvent-to-solid ratio of 200:1 at 120 rpm, 20 MPa pressure and at 35 °C for 60 min by subcritical extraction. Microscopy images showed that most of the cells were disrupted and intracellular components were effectively released. Based on the results of energy dispersive spectroscopy, biomass contained a mixture of organic molecules including mainly carbon (57–72%), oxygen (26–41%), magnesium (0.6–1.4%) and silica (0.4–1%) (wt%). These results make the residual biomass a potential candidate for various areas such as bioenergy, material sciences and sensor technologies.

Description: In a short note of 1998 Davankov questioned the generally accepted notion that the unique features of the planet Earth, namely, the presence of life and atmospheric oxygen are inseparably bonded as a case and effect. Indeed, photosynthesis in terrestrial and aquatic phototrophs simultaneously produces oxygen and carbohydrates in almost equal amounts. Since the degradation of organic matter through burning or rotting also consumes an equivalent amount of oxygen, the total masses of oxygen and organic material must always remain comparable. This correlation for Earth appears to be drastically distorted in favor of oxygen, thus disproving the still widespread delusion of biogenic origin of atmospheric oxygen. Instead, by analyzing more recent data on the balance between oxygen and organics we arrive at the conclusion that radiolysis of water vapors with the preferential dissipation of hydrogen to space, most probably, was the major source of the free and oxidation-spent oxygen. The present review tries to illuminate the most important uncertainties that still remain to be clarified before an interdisciplinary and scientifically-balanced picture on the evolution of Earth gets settled.

Description: The concept of biosorption results from the “passive” (nonmetabolic) interaction of a chemical species with a particle of a biological material. This interaction can be practically exploited, for example, for removal of toxic substances of wastewaters or for the enrichment of a fertilizer with micronutrients. In this work, equilibrium and dynamic data obtained with “low-cost” biomaterials of algal waste or invasive seaweed species have been reviewed and critically analyzed in the context of a circular economy. The concept of a biosorption unit, oriented to the valorization of any solid residual material of algal biomass, can be considered as a real possibility in a biorefinery process; but to accomplish this goal it is necessary that the emphasis on research must definitely move from laboratory scale toward pilot plant assays.

Description: Carnivorous gelatinous zooplankton (GZ) can be very abundant in marine ecosystems around the globe and exert considerable predation pressures on micro- to macrozooplankton as well as larval and juvenile fish. As these species are in many cases intermediate and top predators, their biomass can be easily evaluated, which could indicate overall food web stability or alteration. There is growing concern worldwide about increasing abundances of GZ species and consequently negative impacts on food webs and human coastal zones activities. In this paper, I present a case study from a shallow Danish cove and a long-term record spanning 29 years (1991–2019) obtained by unconventional means. Jellyfish were collected using horizontal sub-surface net tows in August and September during a summer student class. Sea surface temperature and chlorophyll a concentration were measured in parallel. No clear long-term trend in jellyfish biomass could be seen, whereas the values were highly variable from year to year. This is in contrast with other published Scandinavian long-term GZ time series. Sea surface temperature and chlorophyll a concentration had significant (and interactive) effects on the jellyfish biomass in Kertinge Nor. The scarcity and shortness of GZ long-term series do not allow solid conclusions in most marine ecosystems, so it becomes clear that publishing time series (even with small spatial extent) can contribute to improve the perception of interannual GZ population developments. Thus, I strongly recommend extending monitoring activities, explicitly including GZ taxa, in as many marine ecosystems as feasible.

Description: This paper describes methods of obtaining improved estimates of long-term sea level trends for the British Isles. This is achieved by lengthening the sea level records where possible, then removing known sources of variability, and then further adjusting for datum errors that are revealed by the previous processes after verification using metadata from archived sources. Local sea level variability is accounted for using a tide and surge model. Far field variability is accounted for using a “common mode”. This combination reduces the residual variability seen at tide gauges around the coast of the British Isles to the point that a number of previously unrecognised steps in individual records become apparent, permitting a higher level of quality control to be applied. A comprehensive data archaeology exercise was carried out which showed that these step-like errors are mostly coincident with recorded site-specific changes in instrumentation, and that in many cases the periodic tide gauge calibration records can be used to quantify these steps. A smaller number of steps are confirmed by “buddy-checking” against neighbouring tide gauges. After accounting for the observed steps, using levelling information where possible and an empirical fit otherwise, the records become significantly more consistent. The steps are not found to make a large difference to the trend and acceleration observed in UK sea level overall, but their correction results in much more consistent estimates of first order (Sea Level Rise) and second order (Sea Level Acceleration) trends over this 60-year period. We find a mean rate of sea level rise of 2.39 ± 0.27 mm yr−1, and an acceleration of 0.058 ± 0.030 mm yr−2 between Jan. 1958 and Dec. 2018. The cleaner dataset also permits us to show more clearly that the variability other than that derived from local meteorology is indeed consistent around the UK, and relates to sea level changes along the eastern boundary of the North Atlantic.

Description: Fucoxanthin is the major abundant xanthophyll in macro- and micro-algae as a component of photosynthetic light-harvesting complexes for photosynthesis and photoprotection. Nowadays, widespread application of fucoxanthin in food industry, pharmaceutical, and medical purposes are increasing. The current issue attracts the attention of researchers for producing of carotenoid from its natural resources, especially algae. Againts macroalgae, microalgae have rapid growth with the same source of food. In addition, they can grow from variety of situations and environmental conditions to produce a specific biochemical product. Microalgae, e.g. Tisochrysis lutea (T. lutea), can be cultivated under controlled conditions, low cost, and higher concentration of fucoxanthin. This review presents some of nutraceutical effects of fucoxanthin for human health and then, in particular, recent biotechnological developments in bioprocessing of this valuable product including, cultivation, harvesting, extraction, and purification, from T. lutea.

Description: Pretreatment of microalgal biomass possessing rigid cell wall is a critical step for enhancing the efficiency of microalgal biorefinery. However, the conventional pretreatment processes suffer the drawbacks of complex processing steps, long processing time, low conversion efficiency and high processing costs. This significantly hinders the industrial applicability of microalgal biorefinery. The innovative electricity-aid pretreatment techniques serve as a promising processing tool to extensively enhance the release of intracellular substances from microalgae. In this review, application of electric field-based techniques and recent advances of using electrical pretreatments on microalgae cell focusing on pulsed electric field, electrolysis, high voltage electrical discharges and moderate electric field are reviewed. In addition, the emerging techniques integrating electrolysis with liquid biphasic flotation process as promising downstream approach is discussed. This review delivers broad knowledge of the present significance of the application of these methods focusing on the development of electric assisted biomolecules extraction from microalgae.

Description: Coastal communities, knowingly or otherwise, rely on seagrasses for their livelihood, recreation and food source, among other services. However, despite its importance, seagrasses are not receiving similar attentions with its adjacent ecosystems, the mangroves, and coral reefs. Because of their role in climate change mitigation, seagrasses along with mangroves and salt marshes (the blue carbon ecosystems) are gaining attention recently. This preliminary study investigates the perception of coastal communities in Eastern Samar, Philippines on seagrasses. The results of the survey show that there is a level of high awareness among respondents to seagrass ecosystem services. Despite that, however, utilization remains low. The level of awareness varies on the type of ecosystem service; for instance, locals have a high awareness of provisioning services while low awareness of cultural services. The survey also included the perceived threats to seagrasses, where damages caused by natural disturbances are identified as the most concerning threat. This may be due to the geographic location of the sites that are frequented by typhoons. The perception potentially indicates depleted resources brought about by mismanagement or overlooking this natural resource. The results provide a more contextualized understanding on how local communities are aware of and interacting with, or the lack thereof, seagrass ecosystems. This could aid local government units (LGUs) and conservation groups in the area to craft practicable and sustainable management plans and threat-specific solutions.

Description: Simulating complex physical systems often involves solving partial differential equations (PDEs) with some closures due to the presence of multi-scale physics that cannot be fully resolved. Therefore, reliable and accurate closure models for unresolved physics remains an important requirement for many computational physics problems, e.g., turbulence simulation. Recently, several researchers have adopted generative adversarial networks (GANs), a novel paradigm of training machine learning models, to generate solutions of PDEs-governed complex systems without having to numerically solve these PDEs. However, GANs are known to be difficult in training and likely to converge to local minima, where the generated samples do not capture the true statistics of the training data. In this work, we present a statistical constrained generative adversarial network by enforcing constraints of covariance from the training data, which results in an improved machine-learning-based emulator to capture the statistics of the training data generated by solving fully resolved PDEs. We show that such a statistical regularization leads to better performance compared to standard GANs, measured by (1) the constrained model's ability to more faithfully emulate certain physical properties of the system and (2) the significantly reduced (by up to 80%) training time to reach the solution. We exemplify this approach on the Rayleigh-Benard convection, a turbulent flow system that is an idealized model of the Earth's atmosphere. With the growth of high-fidelity simulation databases of physical systems, this work suggests great potential for being an alternative to the explicit modeling of closures or parameterizations for unresolved physics, which are known to be a major source of uncertainty in simulating multi-scale physical systems, e.g., turbulence or Earth's climate.

Description: Microalgae are a rich source of natural bioactive compounds, e.g. astaxanthin, β-carotene, lutein, and fatty acids (FAs), that are currently in high demand in the market. Conventional extraction methods often produce adverse effects on some of these compounds. Replacing conventional extraction methods with more efficient advanced green technologies that offer greater extracts purity and low environmental impact is therefore a challenging and sought-for target. This review is a comprehensive overview of supercritical fluid (SCF) extraction processes, including the latest research on the extraction of bioactive compounds from microalgae biomass and their benefits on human health. In addition, the role of key operating parameters on the selectivity of various compounds is discussed. This study provides useful knowledge that can productively contribute to the future development of SCF-based extraction technologies on an industrial scale.

Description: Aging entails an irreversible deceleration of physiological processes, altered metabolic activities, and a decline of the integrity of tissues, organs, and organ systems. The accumulation of alterations in the genetic and epigenetic spaces has been proposed as an explanation for aging. They result, at least in part, from DNA replication and chromosome segregation errors due to cell division during development, growth, renewal, and repair. Such deleterious alterations, including epigenetic drift, irreversibly accumulate in a stepwise, ratchet-like manner and reduce cellular fitness, similar to the process known as Muller’s ratchet. Here, we revisit the Muller’s ratchet principle applied to the aging of somatic cell populations and discuss the implications for understanding the origins of senescence, frailty, and morbidity.

Description: Natural cycles in the seawater partial pressure of carbon dioxide (CO2) in the Gulf of Maine, which vary in surface waters from ~250 to 550 µatm seasonally, provide an opportunity to observe how the life cycle and phenology of the shelled pteropod Limacina retroversa responds to changing food, temperature and carbonate chemistry conditions. Distributional, hydrographic, and physiological sampling suggest that pteropod populations are located in the upper portion of the water column (0–150 m) with a maximum abundance above 50 m. Gene expression and shell condition measurements show that the population already experiences biomineralization stress in the winter months when measured aragonite saturation state was at a seasonal low (though slightly oversaturated), reinforcing the usefulness of this organism as a bio-indicator for pelagic ecosystem response to ocean acidification. There appear to be two reproductive events per year with one pulse timed to coincide with the spring bloom, the period with highest respiration rate, fluorescence, and pH, and a second more extended pulse in the late summer and fall when saturation states remain high and fluorescence begins to decline. During the fall there is transcriptomic evidence of lipid storage for overwintering, allowing the second generation to survive the period of low food and aragonite saturation state. Based on these observations we predict that in the future pteropods will likely be most vulnerable to changing CO2 regionally during the fall reproductive event when CO2 concentration already naturally rises and when there is the added stress of generating lipid stores.

Description: We use numerical simulations on petrographically characterized thin-section images to predict three-dimensional elastic compressibility of sandstones. We predict two key statistics of compressibility curves measured under uniaxial boundary conditions in a laboratory - i) minimum compressibility at 1500 psi or 10 MPa depletion stress, and ii) maximum compressibility. A new Digital Rock workflow was developed for predicting compressibility based on the simulation of stress field using a segmented two-dimensional thin-section image. We also propose linear and non-linear relationships of log base 10 (compressibility) with in-situ porosity that can be used for compressibility prediction in the absence of laboratory measurements or two-dimensional images. Based on the results of application of the proposed relationships on samples from different fields with laboratory measurements, we conclude that the best prediction for minimum compressibility is obtained using the Digital Rock workflow and the best prediction for maximum compressibility is obtained using the proposed non-linear relationship using in-situ porosity. The range of compressibility values given by the difference between maximum and minimum compressibility predicted using the proposed methods can be used in making better informed economic decisions in field development planning.

Description: Pteropods are holopelagic marine snails and slugs that are of particular interest to science due to their role in marine food webs, global carbon cycle and their potential sensitivity to ocean change. Due to their pelagic, often exclusively offshore occurrence, samples are difficult to obtain, resulting in a lack of knowledge about their physiology, ecology, anatomy, geographical ranges, phylogenetic relationships and reproductive biology. Despite a recent increase in interest surrounding pteropod taxonomy, many evolutionary uncertainties remain due to limited taxon sampling and inavailability of molecular vouchers, in particular for the lesser investigated groups Pseudothecosomata and Gymnosomata. The Northwest Pacific Ocean is one of the least investigated areas for pteropods and in the adjacent semi-enclosed Sea of Okhotsk basin, current knowledge is restricted to the epipelagic zone. We summarize results from plankton hauls (from up to 5900 m depth) conducted during the joint German/Russian SokhoBio and KuramBio II cruises to the Sea of Okhotsk and the Kuril-Kamchatka-Trench region. This study presents an integrative taxonomic overview of six pteropod species identified by detailed morphological methods, including serial semithin sectioning, µCT and SEM scanning supported by multimarker (COI, 28S, and H3) genetic barcoding. We found four species of Gymnosomata slugs (Clione limacina, Clione okhotensis, Notobranchaea grandis and Thliptodon sp.), three species of Euthecosomata snails (Limacina helicina and two genetically delimited Clio spp.) and one shelled pseudothecosome species that is probably new to science (Peracle n. sp.). Multilocus phylogenetic analyses support monophyly of major traditional groups such as Pteropoda, Thecosomata, Pseudothecosomata and Gymnosomata. Micro-CT scanning was applied for the first time on pteropod soft bodies, allowing direct comparison between detailed anatomical peculiarities and molecular barcodes of the respective species. Furthermore, taxonomic positions, geographical ranges and potential dispersal barriers are discussed, with implications for future biodiversity comparisons. This study serves as a solid foundation for monitoring pteropods in a changing ocean.

Description: Hybrid chemical compounds formed by conjugation of two or more bioactive molecules have shown wide variety of applications in biology, microelectronics as well as material sciences. In particular, the conjugates of steroid framework are known to have broad biological activity profile due to their ability to penetrate the biomembranes and bind to specific hormone receptors. Among the various conjugates of steroids, Steroid Amino Acid Conjugates (SAACs) are attractive because of the possibility of fine tuning of the amphiphilicity with position, orientation and nature of amino acids. The structural details, applications, mechanistic insights and their diverse pharmacological as well as other physicochemical properties of several SAACs are summarized in the present review. This review provides better insight for medicinal chemists to design and explore such novel conjugates which can be used as lead structures in the future drug discovery or as probes to understand the complex biological system.

Description: Microalgal oils are considered an important source of industrially valuable oleochemicals with significant applications ranging from the energy to pharmaceutical sectors. Industrial production of microalgal oil is emerging rapidly; however, the high cost associated with downstream processes may constrain this process. Oils are accumulated intracellularly in oleaginous microalgae in the form of lipid droplets, which in turn require cell wall disruption followed by extraction in order to recover them. Disruption of the microalgal cell is very challenging owing to its distinctive features like high water content, hard cell wall, presence of algaenan, and sporopollenin like biopolymers that in turn create hurdles in efficient extraction of lipids. Various conventional pretreatment methods have been explored to rupture the cellular integrity of microalgal cells to enhance lipid extraction, and each method has certain advantages and disadvantages. Supercritical fluid extraction is the oldest technique for the extraction of valuable compounds from microalgae and is considered an alternative to conventional solvent extraction methods. It has several advantageous features such as being free from organic solvents (and their disposal), environment-friendly, and operating at a mild range of temperature (40–80°C). CO2 is considered to be an ideal supercritical fluid due to its non-toxic, non-flammable, and lipophilic nature. In this chapter, use of supercritical carbon dioxide extraction of lipids from microalgae is discussed and compared with other available lipid extraction methods.

Description: Cell disruption is regarded as an indispensable pretreatment step before the extraction of microalgae with biomineralized cell walls. Here, two typical microalgae—diatom Chaetoceros gracilis (C. gracilis) and coccolithophore Pleurochrysis carterae (P. carterae)—covered by “hard” biomineralized cell walls were used as starting materials for lipid extraction using liquefied dimethyl ether (DME) without any pretreatment such as drying or cell disruption. The liquefied DME extraction experiments were performed at 25 °C and 0.59 MPa using a semi-continuous, flow-type system. The results of the yield, elemental composition, molecular weight distribution, fatty acid composition, and trace element composition indicated that the performance of liquefied DME extraction was similar to that of Bligh–Dyer extraction and better than that of hexane Soxhlet extraction, despite the latter two methods requiring pre-drying and cell disruption processes. It was also proven that the cell wall of microalgae would not affect lipid extraction of liquefied DME, thereby the liquefied DME extraction method is suitable for extracting lipids from microalgae with biomineralized cell walls. Besides, the lipids extracted by liquefied DME can be further used for biodiesel production.

Description: In recent years, metagenomic strategies have been widely used to isolate and identify new enzymes from uncultivable components of microbial communities. Among these enzymes, various lipases have been obtained from metagenomic libraries from different environments and characterized. Although many of these lipases have characteristics that could make them interesting for application in biocatalysis, relatively little work has been done to evaluate their potential to catalyze industrially important reactions. In the present article, we highlight the latest research on lipases obtained through metagenomic tools, focusing on studies of activity and stability and investigations of application in biocatalysis. We also discuss the challenges of metagenomic approaches for the bioprospecting of new lipases.

Description: There are no effective therapies for achondroplasia. An open-label study suggested that vosoritide administration might increase growth velocity in children with achondroplasia. This phase 3 trial was designed to further assess these preliminary findings. Methods This randomised, double-blind, phase 3, placebo-controlled, multicentre trial compared once-daily subcutaneous administration of vosoritide with placebo in children with achondroplasia. The trial was done in hospitals at 24 sites in seven countries (Australia, Germany, Japan, Spain, Turkey, the USA, and the UK). Eligible patients had a clinical diagnosis of achondroplasia, were ambulatory, had participated for 6 months in a baseline growth study and were aged 5 to less than 18 years at enrolment. Randomisation was done by means of a voice or web-response system, stratified according to sex and Tanner stage. Participants, investigators, and trial sponsor were masked to group assignment. Participants received either vosoritide 15·0 μg/kg or placebo, as allocated, for the duration of the 52-week treatment period administered by daily subcutaneous injections in their homes by trained caregivers. The primary endpoint was change from baseline in mean annualised growth velocity at 52 weeks in treated patients as compared with controls. All randomly assigned patients were included in the efficacy analyses (n=121). All patients who received one dose of vosoritide or placebo (n=121) were included in the safety analyses. The trial is complete and is registered, with EudraCT, number, 2015-003836-11. Findings All participants were recruited from Dec 12, 2016, to Nov 7, 2018, with 60 assigned to receive vosoritide and 61 to receive placebo. Of 124 patients screened for eligibility, 121 patients were randomly assigned, and 119 patients completed the 52-week trial. The adjusted mean difference in annualised growth velocity between patients in the vosoritide group and placebo group was 1·57 cm/year in favour of vosoritide (95% CI [1·22–1·93]; two-sided p〈0·0001). A total of 119 patients had at least one adverse event; vosoritide group, 59 (98%), and placebo group, 60 (98%). None of the serious adverse events were considered to be treatment related and no deaths occurred. Interpretation Vosoritide is an effective treatment to increase growth in children with achondroplasia. It is not known whether final adult height will be increased, or what the harms of long-term therapy might be.

Description: Biofouling is a challenge in global sea-based salmon farming. Norway's salmon-growing industry relies primarily on copper-based antifouling coatings. However, copper is an increasingly recognised environmental hazard, and there is a need to develop alternative antifouling products to prevent biofouling in marine aquaculture. Using field experiments, this study compared the efficacy of six novel antifouling coatings for fish farm nets (two with reduced copper content, three with alternative biocides and one biocide-free coating) against a popular commercial copper coating and uncoated samples. The performance of one of the new coatings with lower copper content was more similar to the commercial copper control while the rest were colonised by biofouling faster and/or at higher abundances. However, none of the tested products were able to prevent biofouling entirely, underlining the importance of the search for alternative and improved antifouling technologies.

Description: Seagrass meadows are important productive ecosystems; during the Summer period in touristic beaches, such as those located in the high Adriatic coast, seagrasses are removed from the shoreline and disposed in landfill. This study investigated anaerobic digestion potential of beach-cast seagrass wrack, considering the physicochemical characteristics of the substrate and analysing heavy metal presence in the digestate, with the aim of transporting the material to local wastewater treatment plants to increase biogas yield from excess sludge anaerobic digestion. The methane production obtained from seagrass wrack was compared with three theoretical models. Seagrass wrack had a good methane potential of 103.1–262.3 NmL CH4/g Volatile Solids (VS), depending on substrate humidity and applied inoculum-to-substrate ratio. Predictive models, based on elemental composition and proximate analysis, successfully estimated methane yields; heavy metal concentration in digestate was low, boosting for digestate agricultural reuse. A simplified energy analysis revealed that transport to local wastewater treatment plants and use in anaerobic digestion process would provide up to 245,000 Nm3/y of methane, with an estimated economic income of 33,500–193,300 €/y, considering local seagrass production (1,465–8,454 t/y). Actual yearly costs sustained by beach management company for landfill disposal was about 117,200–676,320 €/y. Seagrass reuse in local digesters would compensate for the lack of excess sludge encountered during the cold season, allowing the digester to operate more continuously, increasing biogas production and reducing plant energy need.

Description: The analysis of more than 400 papers found in the literature on Sargassum biosorption has shown the existence of more than 700 equilibrium entries corresponding to data at different temperature and pH conditions. The following ten single metals: Cd, Co, Cr(III, VI), Cu, Fe, Hg, La, Ni, Pb, and Zn, are the main focus of most of the equilibrium data (507) in more than half of the studied references. The studies reflecting the interaction of nine of these metals with Sargassum sp. is described and analyzed. The use of Langmuir equation, the effect of temperature and pH on sorption is critically reviewed. In addition, we also analyze all the data available on elemental chemical composition of native Sargassum. These data reflect the interaction of this kind of marine biomass with nine of the metals mentioned above, which are present in seawater worldwide.

Description: Six new compounds including two azaphilones, lunatoic acids D–E (1, 2), three isocoumarins, lunatinins B–D (3-5), and one α-pyrone derivative, lunatinin E (6), as well as four known ones, lunatoic acid A (7), lunatinin (8), penicipyran D (9) and chaetoquadrin F (10) were isolated from the rice medium of the gut fungus Paraphaeosphaeria sp. XZD2-1. Their planar structures were elucidated by analysis of 1D and 2D NMR as well as HRESIMS spectroscopic data. The absolute configurations of compounds 1-3 were assigned by experimental and calculated ECD data and an ester hydrolysis reaction. Compounds 4 and 5 were a pair of enantiomeric excess mixture. Structure of compound 6 was further confirmed by comparing optical rotation with known compounds according to literature. The antimicrobial activity and cytotoxicity of compounds 1-10 were examined.

Description: As the frequency and intensity of storms increase, a growing need exists for resilient shore protection techniques that have both environmental and economic benefits. In addition to producing seafood, aquaculture farms may also provide coastal protection benefits either alone or with other nature-based structures. In this paper, a generalized three-layer frequency dependent theoretical model is derived for random wave attenuation due to presence of biomass within the water column. The biomass can be characterized as submerged, emerged, suspended and floating canopies that can consist of natural aquatic vegetation with potential aquaculture systems of kelp or mussels. The present analytical solutions can reduce to the solutions by Mendez and Losada (2004), Chen and Zhao (2012) and Jacobsen et al. (2019) for submerged rigid aquatic vegetation. The present theoretical model incorporates the motion of these canopies using a cantilever-beam model for slender components and a buoy-on-rope model for elements with concentrated mass and buoyancy. Analytical results are compared with existing laboratory and field datasets for submerged and suspended canopies. The theoretical model was then used (in a case study at a field site in Northeastern US) to investigate the capacity of suspended mussel farms with submerged aquatic vegetation (SAV) to dissipate wave energy during a recent storm event. Compared to a dense SAV meadow in shallower water, the suspended aquaculture farms more effectively attenuate random waves with a smaller peak period and the higher frequency components of wave spectrum. The performance of suspended aquaculture farms is less affected by water level changes due to tides, surge and sea level rise, while the wave attenuation performance of SAV decreases with increasing water level due to decreased wave motion near the sea bed. Incorporating suspended aquaculture farms offshore significantly enhance the coastal protection effectiveness of SAV-based living shorelines and extend the wave attenuation capacity over a wider wave period and water level range. The combination of suspended aquaculture farms and traditional living shorelines provides a more effective nature-based coastal defense strategy than the traditional living shorelines alone.

Description: Application of polyester-degrading enzymes should be considered as an eco-friendly alternative to chemical recycling due to the huge plastic waste disposal nowadays. Many hydrolases from several fungi and bacteria have been discovered and successfully evaluated for their activity towards different aliphatic polyesters (PHA, PBS, PBSA, PCL, PLA), aromatic polyesters (PET, PBT, PMT) as well as their co-polyesters (PBST, PBAT, PBSTIL). This revision gives an up-to-date overview on the main biochemical features and biotechnological applications of those reported enzymes which are able to degrade polyester-based plastics, including different microbial polyester depolymerases, esterases, cutinase-like enzymes and lipases. Summarized information includes available protein sequences with the corresponding accession numbers deposited in NCBI server, 3D resolved structures, and data about optimal conditions for enzymatic activity and stability of many of these microbial enzymes that would be helpful for researchers in this topic. Although screening and identification of new native polyester hydrolases from microbial sources is undeniable according to literature, we briefly highlight the importance of the design of improved enzymes towards recalcitrant aromatic polyesters through different approaches that include site-directed mutagenesis and surface protein engineering.

Description: The subpopulation of Atlantic cod, Gadus morhua, in the eastern part of the Baltic Sea has experienced a significant increase in infections with anisakid nematode larvae of the species Contracaecum osculatum sensu lato (s.l.) since the year 2000. The life cycle of the parasite includes seals and especially the grey seal, Halichoerus grypus, as final hosts, carrying the adult nematodes in the stomach, crustaceans (copepods, amphipods) as first intermediate hosts and various fish species (clupeids, sandeel) including cod as second intermediate/paratenic hosts. Cod with a body length below 28 cm are generally non-infected but experience increasing infection levels when they switch to a piscine diet (infected intermediate/paratenic hosts). We present an overall frequency distribution analysis of worms in 166 cod (body length 30–49 cm) collected in the spawning area over the last 5 years. It shows a fit to the negative binomial distribution, a prevalence of infection of 89.8%, a mean intensity of 29.3 parasites per fish (range 1–377) and a variance/mean ratio of 59.2 (≫1), indicating overdispersion. We present measurements of the adult Contracaecum osculatum (s.l.) specimens in the seal stomach and show that the parasites reach a maximum length of 6.6 cm (females) and 5.8 cm (males). L3s in sprat have a total length from 1to 11 mm whereas the larvae in cod liver are 3–27 mm. A decreasing mean worm length associated with high worm densities in cod (number of nematodes per liver) was recorded. Possible explanations might include timing of feeding on infected intermediate/paratenic hosts, intraspecific competition (crowding) between larvae in cod and host responses (indicated by a significant antibody production in cod against C. osculatum (s.l.) antigens). A significant negative correlation between infection intensity and muscle mass of cod was found, suggesting parasite-induced down-regulation of growth factors in cod.

Description: Despite their critical role as the main energy pathway between phytoplankton and fish, the functional complexity of zooplankton is typically poorly resolved in marine ecosystem models. Trait-based approaches—where zooplankton are represented with functional traits such as body size—could help improve the resolution of zooplankton in marine ecosystem models and their role in trophic transfer and carbon sequestration. Here, we present the Zooplankton Model of Size Spectra version 2 (ZooMSSv2), a functional size-spectrum model that resolves nine major zooplankton functional groups (heterotrophic flagellates, heterotrophic ciliates, larvaceans, omnivorous copepods, carnivorous copepods, chaetognaths, euphausiids, salps and jellyfish). Each group is represented by the functional traits of body size, size-based feeding characteristics and carbon content. The model is run globally at 5° resolution to steady-state using long-term average temperature and chlorophyll a for each grid-cell. Zooplankton community composition emerges based on the relative fitness of the different groups. Emergent steady-state patterns of global zooplankton abundance, biomass and growth rates agree well with empirical data, and the model is robust to changes in the boundary conditions of the zooplankton. We use the model to consider the role of the zooplankton groups in supporting higher trophic levels, by exploring the sensitivity of steady-state fish biomass to the removal of individual zooplankton groups across the global ocean. Our model shows zooplankton play a key role in supporting fish biomass in the global ocean. For example, the removal of euphausiids or omnivorous copepods caused fish biomass to decrease by up to 80%. By contrast, the removal of carnivorous copepods caused fish biomass to increase by up to 75%. Our results suggest that including zooplankton complexity in ecosystem models could be key to better understanding the distribution of fish biomass and trophic efficiency across the global ocean.

Description: Mitigating human contributions to climate change is a highly debated topic, as it becomes evident that many nations do not adhere to optional reductions in global emission. Substantial research is taking place into negative carbon technologies that actively reduce the amount of atmospheric carbon dioxide (CO2) via greenhouse gas removal (GGR). Various GGR methods have been proposed, from reforestation to ocean fertilisation. This article discusses advantages of an approach based on enhanced input of tephra to the ocean, to increase the drawdown of atmospheric CO2. Natural addition of tephra to the ocean results in preservation of enhanced organic matter in sediment. Hence, augmenting its delivery should raise the level of sequestration. Calculations indicate that offshore tephra addition could sequester 2750 tonnes of CO2 per 50,000 tonnes of ash delivered (a typical bulk carrier’s capacity). The cost is estimated as ∼$55 per tonne of CO2 sequestered and is an order of magnitude cheaper than many proposed GGR technologies. Further advantages include: tephra addition is simply an augmentation of a natural Earth process, it is a low technology approach that requires few developments, and it may sequester carbon for thousands of years. Hence, offshore tephra addition warrants further investigation to assess its viability.

Description: Subsurface-intensified anticyclones are ubiquitous in the ocean, yet their impact on the large-scale transport of heat, salt and chemical tracers is poorly understood. These submesoscale coherent vortices (SCVs) can trap and advect waters thousands of kilometers away from the formation region, providing a transport pathway that is unresolved by low-resolution Earth System Models. However, knowledge of the importance of these eddies for the large scale circulation is hindered by the lack of systematic observations. Here, we take advantage of the global network of Argo floats to identify occurrences of these eddies, which appear as weakly stratified anomalous water masses with Gaussian-shaped vertical structures. We develop a general algorithm to detect subsurface eddies that have propagated away from their source region, and apply it to the database of Argo float profiles, resulting in roughly 4000 detections from more than 20 years of observations. We further group detections into regional populations to identify hot-spots of generation and mechanisms of formation. Analysis of regional SCV statistics reveals important sites of SCV generation in Eastern Boundary Upwelling Systems, marginal sea overflows, and mode water formation regions along major open-ocean fronts. Because of the heat and salt anomaly contained within their cores, SCV could leave a significant imprint on the hydrographic properties of water masses in regions of high SCV density.

Description: Used during an oil spill to minimise the formation of an oil slick, dispersants have negative biological effects on marine model organisms. However, no study has investigated the impacts of dispersants on adult sponge individuals. Here, we examine the effects of water accommodated oil fraction (WAF - oil in seawater), chemically enhanced WAF (CEWAF - oil and dispersant in seawater) and Benzo[A]Pyrene on sponge Halichondria panicea at physiological and molecular levels. Sponge clearance rate decreased sharply when exposed to WAF and CEWAF but the oil loading at which the clearance rate was reduced by 50% (ED50) was 39-fold lower in CEWAF than in WAF. Transcriptomic analysis revealed a homogenous molecular response with the greatest number of differentially expressed genes identified in CEWAF samples (1,461 genes). Specifically, genes involved in stress responses were up-regulated. This study presents evidence that the use of dispersants should be considered carefully in areas where sponges are present.

Description: This study evaluated the application of a Halobacteriovorax isolated from water of the Adriatic Sea (Italy) in controlling V. parahaemolyticus in mussels (Mytilus galloprovincialis). Two 72 h laboratory-scale V. parahaemolyticus decontamination experiments of mussels were performed. The test microcosm of experiment 1 was prepared using predator/prey free mussels experimentally contaminated with Halobacteriovorax/V. parahaemolyticus at a ratio of 103 PFU/105 CFU per ml, while that of experiment 2 using mussels naturally harbouring Halobacteriovorax that were experimentally contaminated with 105 CFU per ml of V. parahaemolyticus. For experiment 1, was also tested a control microcosm only contaminated with 105 CFU per ml of V. parahaemolyticus.. Double layer agar plating and pour plate techniques were used to enumerate Halobacteriovorax and V. parahaemolyticus, respectively. 16 S rRNA analysis was used to identify Halobacteriovorax. For both experiments in the test microcosm the concentration of prey remained at the same level as that experimentally added, i.e. 5 log for the entire analysis period. In experiment 1, V. parahaemolyticus counts in mussels were significantly lower in the test microcosm than the control with the maximum difference of 2.2 log at 24 h. Results demonstrate that Halobacteriovorax can modulate V. parahaemolyticus level in the mussels. The public impact of V. parahaemolyticus in bivalves is relevant and current decontamination processes are not always effective. Halobacteriovorax is a suitable candidate in the development of a biological approach to the purification of V. parahaemolyticus in mussels.

Description: The ctenophore Mnemiopsis leidyi, ranking among the 100 most damaging bioinvaders in the world, is a major predator of zooplankton, known to alter the biodiversity and functioning of the ecosystems in which it has been introduced. This first survey on the trophic relationships of M. leidyi in a Mediterranean lagoon (Berre, South of France) was performed through stable isotope analyses. Carbon and nitrogen isotope composition was used (1) to determine the types of prey ingested by this ctenophore and (2) the influence of individual size on its isotope composition, and (3) to make assumptions to explore its trophic relationships with the native jellyfish Aurelia sp.. The two gelatinous species ingested mainly (79% to 97% of the diet) planktonic prey (copepods, cirriped nauplii, gastropod larvae and cladocerans), but also preyed upon benthic organisms (mainly harpacticoid copepods and the amphipod Monocorophium insidiosum) in lower proportions (2.5% to 21%). Size-related changes in M. leidyi diet were evidenced with an increase in trophic level and benthic prey consumption in the larger individuals. These two gelatinous organisms probably play an important and underestimated role in the benthic–pelagic​ coupling in coastal lagoons by transferring benthic organic matter to the pelagic food webs.

Description: Santorini, Greece is a major explosive volcano. The Santorini volcanic complex is composed of two active volcanoes—Nea Kameni and Mt. Columbo. Holocene eruptions have generated a variety of processes and deposits and eruption mechanisms pose significant hazards of various types. It has been recognized that, for major European volcanoes, few studies have focused on the social aspects of volcanic activity and little work has been conducted on public perceptions of hazard, risk and vulnerability. Such assessments are an important element of establishing public education programmes and developing volcano disaster management plans. We investigate perceptions of volcanic hazards on Santorini. We find that most residents know that Nea Kameni is active, but only 60% know that Mt. Columbo is active. Forty percent of residents fear that negative impacts on tourism will have the greatest effect on their community. In the event of an eruption, 43% of residents would try to evacuate the island by plane/ferry. Residents aged N50 have retained a memory of the effects of the last eruption at the island, whereas younger residents have no such knowledge. We find that dignitaries and municipal officers (those responsible for planning and managing disaster response) are informed about the history, hazards and effects of the volcanoes. However, there is no bemergency planQ for the island and there is confusion between various departments (Civil Defense, Fire, Police, etc.) about the emergency decision-making process. The resident population of Santorini is at high risk from the hazards associated with a future eruption.

Description: Late glacial to post glacial sea-level changes provide direct evidence of the progress of melting of large ice sheets during the last deglaciation but, although the correlation between ice and ocean volumes is incontrovertible, the causal link is commonly obscured. Local effects including tectonics, isostatic and hydroisostatic responses and equatorial ocean-syphoning impose additional signals that hide the true picture. A detailed regional study of the Western Indian Ocean based on the analysis of drill cores carried out through modern reefs, in combination with observations and sampling of reef foreslopes, and investigations of outcrops provides a comprehensive data base. Sites from a range of tectonic settings include the microcontinental margins of Madagascar, the granitic Seychelles, and the isolated volcanic islands of Réunion, Mauritius and the Comoros in which the effects of subsidence can be shown to be small. These cover a range of latitudes, and comparisons with adjacent sites on continental margins allow the construction of sea-level curves that closely reflect the eustatic response and disengage this from the effects of other mechanisms. The Mayotte foreslope in the Comoro Islands provides the first coral reef record of sea-level change during the early deglaciation in the Indian Ocean (110–115 m below present sea level between 18,000 and 17,000 yr BP). Two distinctive reef terraces, at 90 and 60 m water depth are dated at 13,600 yr BP and partly attributed to the Younger Dryas period (12,700–11,600 cal yr BP). Reef drowning at around 13,500 yr BP may correspond to Meltwater Pulse 1A, and although there were surges in the rate of sea-level rise, most notably between 11,950 and 11,350 yr BP, there is little evidence to support a well-defined Meltwater Pulse 1B. Reconstructed Holocene sea-level curves are in good agreement and reflect a rapid sea-level rise of about 6 mm yr−1 between 10,000 and 7500 yr BP, followed by a clear inflection around 7500 yr BP when the rate fell to 1.1 mm yr−1. Modern reefs started to grow 8000–9000 years ago. In the post-glacial period the rate of sea-level rise was 1–1.5 mm yr−1 before stabilization at its present level 3000–2500 years ago. Curves for the 10,000–6000 yr−1 BP interval correspond closely with those predicted by theoretical models but lie below these in the subsequent period. In particular, and with the exception of the margins of the Madagascar microcontinent influenced by hydroisostatic processes, they do not reflect predicted higher sea-level stands during the late Holocene.

Description: New data obtained during re-mapping of the northern part of Syros (Cyclades, Greece) allow the refinement of existing concepts about the structural evolution of this island. A metabasite belt and its metasedimentary envelope near Kampos and San Michali were mapped at a 1:5000 scale, with special emphasis on the structural inventory. The HP/LT rocks (P , 1.5 GPa; T , 500 8C at ,50 Ma) exposed are intensely deformed by at least two isoclinal folding events. Relative age relations between deformation and peak metamorphism indicate that isoclinal folding took place before or during peak metamorphism. Later deformation stages include Miocene non-penetrative upright kink folding and crenulation, transpressional strike-slip faulting, and open upright cylindrical folding, followed by the development of steep normal faults. Taking into account recent zircon U–Pb geochronological constraints, lithostratigraphic observations, and published data on the Neogene structural evolution of the Aegean, we present a history for the rocks of Syros, beginning with the formation of the oceanic crust(represented by the metabasites) to the present.

Description: Measurements of δ18O and δ13C isotopes in three benthic foraminiferal species from surface sediments of the eastern Laptev Sea are compared to water δ18O values and δ13C values of dissolved inorganic carbon (DIC). Samples investigated originate from two environmentally contrasting core locations, which are influenced by riverine freshwater runoff to a varying degree. At the river-distal site, located within relatively stable marine conditions on the outer shelf, Elphidiella groenlandica, Haynesina orbiculare and Elphidium excavatum forma clavata show a positive specific offset of 1.4‰, 1.5‰ and 1‰, respectively, in their δ18O values relative to the expected value for inorganic calcite precipitated under equilibrium conditions. At the site close to the Lena River confluence, with enhanced seasonal hydrographic contrasts, calculated δ18O offsets in E. groenlandica and in H. orbiculare remain about the same whereas E. e. clavata displays a distinctly negative offset of −1.8‰. The δ18O variation in E. e. clavata is interpreted as a vital effect, a finding which limits the potential of this species for reconstructing freshwater-influenced shelf paleoenvironments on the basis of oxygen isotopes. This interpretation gains support when comparing foraminiferal δ13C with the δ13CDIC of the water. While some of the difference in the carbonate δ13C seems to be controlled by a riverine-related admixture of DIC, clearly defined δ13C ranges in each of the three foraminifera at the river-proximal site shows that also the carbon isotopic signature in E. e. clavata is particularly affected by environmental factors.

Description: Extensive methane hydrate layers are formed in the near-surface sediments of the Cascadia margin. An undissociated section of such a layer was recovered at the base of a gravity core (i.e. at a sediment depth of 120 cm) at the southern summit of Hydrate Ridge. As a result of salt exclusion during methane hydrate formation, the associated pore waters show a highly elevated chloride concentration of 809 mM. In comparison, the average background value is 543 mM. A simple transport-reaction model was developed to reproduce the Cl- observations and quantify processes such as hydrate formation, methane demand, and fluid flow. From this first field observation of a positive Cl- anomaly, high hydrate formation rates (0.15–1.08 mol cm-2 a-1) were calculated. Our model results also suggest that the fluid flow rate at the Cascadia accretionary margin is constrained to 45–300 cm a-1. The amount of methane needed to build up enough methane hydrate to produce the observed chloride enrichment exceeds the methane solubility in pore water. Thus, most of the gas hydrate was most likely formed from ascending methane gas bubbles rather than solely from CH4 dissolved in the pore water.

Description: A composite record (LO09-14) of three sediment cores from the subpolar North Atlantic (Reykjanes Ridge) was investigated in order to assess surface ocean variability during the last 11 kyr. The core site is today partly under the influence of the Irminger Current (IC), a branch of the North Atlantic Drift continuing northwestward around Iceland. However, it is also proximal to the Sub-Arctic Front (SAF) that may cause extra dynamic hydrographic conditions. We used statistical methods applied to the fossil assemblages of diatoms to reconstruct quantitative sea surface temperatures (SSTs). Our investigations give evidence for different regional signatures of Holocene surface oceanographic changes in the North Atlantic. Core LO09-14 reveal relatively low and highly variable SSTs during the early Holocene, indicating a weak IC and increased advection of subpolar water over the site. A mid-Holocene thermal optimum with a strong IC occurs from 7.5 to 5 kyr and is followed by cooler and more stable late Holocene surface conditions. Several intervals throughout the Holocene are dominated by the diatom species Rhizosolenia borealis, which we suggest indicates proximity to a strongly defined convergence front, most likely the SAF. Several coolings, reflecting southeastward advection of cold and ice-bearing waters, occur at 10.4, 9.8, 8.3, 7.9, 6.4, 4.7, 4.3 and 2.8 kyr. The cooling events recorded in the LO09-14 SSTs correlate well with both other surface records from the area and the NADW reductions observed at ODP Site 980 indicating a surface-deepwater linkage through the Holocene.

Description: Variability in the chemical composition, textures and electrical properties of the major sulphide mineral pyrite may be one cause of variation in the flotation and leaching properties of different sulphide ores. This report summarises the results of a review that has been conducted to establish the range in variability of natural pyrite with regard to chemical composition, texture and electrical properties. The S/Fe ratio in pyrite is generally very close to 2, suggesting that stoichiometric variability is small in this mineral. However, minor deviations from the ideal are reported. Pyrite typically contains a host of minor and trace elements, including: Ag, As, Au, Bi, Cd, Co, Cu, Hg, Mo, Ni, Pb, Pd, Ru, Sb, Se, Sb, Sn, Te, Tl and Zn. Minor elements are often present within the mineral lattice at levels up to several percent, these include; As, Co, Ni, Sb and possibly Cu, Ag, Au and Sn. Arsenian pyrites may contain up to 10% As, and such specimens are typically rich in other minor and trace elements, particularly Au. As-rich pyrites typically appear to have formed at relatively low temperatures and often exhibit habits that suggest rapid precipitation; these As-rich pyrites may be metastable and, therefore, relatively reactive. Considerable variation has been reported in the semiconducting properties of pyrite. Natural pyrites are either n- or p-type semiconductors and reported conductivities vary by four orders of magnitude. The rates of galvanic processes in mineral pulps are likely to vary with the mineral conductivities. Typically p-type pyrites exhibit low conductivities and are As-rich and are suggested to have formed at relatively low temperature, whereas relatively highly conducting n-type pyrites are typically As-poor and suggested to have formed at high temperature. Based on comparative measurements of rest potential, iron pyrite is the most electrochemically inert of the common sulphide minerals, with a rest potential of the order of 0.6 (cf. sphalerite and galena with rest potentials of 0.46 and 0.40 V. vs. SHE, respectively). Variability in the rest potential of different samples of this mineral are generally small. However, based on the extent of pyrite reaction during a peroxide dissolution procedure, the chemical reactivity of pyrite samples may differ significantly.

Description: A continuous lacustrine sequence from the western part of Lama Lake (69°32′N, 90°12′E), complemented by a peat sequence from the lake catchment provides the first detailed environmental reconstruction for the Late Glacial and Holocene on the Taymyr Peninsula. Scarce steppe-like communities with Artemisia, Poaceae, and Cyperaceae dominated during the Late Glacial. Tundra-like communities with Betula nana, Dryas, and Salix grew on more mesic sites. There are distinct climatic signals, which may be correlated with the Bølling and Allerød warming and Middle and Younger Dryas cooling. The Late Glacial/Preboreal transition, at about 10,000 14C yr BP, was characterized by changes from predominantly open herb communities to shrub tundra ones. Larch forest might have been established as early as 9700–9600 14C yr BP, whilst shrub alder came to the area ca 9500–9400 14C yr BP, and spruce did not reach area before ca 9200 14C yr BP. Spruce-larch forests with shrub alder and tree birch dominated the vegetation around the Lama Lake from ca 9000 14C yr BP. Dwarf birch communities were also broadly distributed. The role of spruce in the forest gradually decreased after 4500 14C yr BP. The vegetation cover in the Lama Lake area became similar to the modern larch-spruce forest ca 2500 14C yr BP. A pollen-based biome reconstruction supports a quantitative interpretation of the pollen spectra. Climate reconstructions obtained with information-statistical and plan-functional-type methods show very similar trends in reconstructed July temperature since ca 12,300 14C yr BP, while precipitation anomalies are less coherent, especially during the Late Glacial–Holocene transition.

Description: Radiocarbon-dated pollen, rhizopod, chironomid and total organic carbon (TOC) records from Nikolay Lake (73°20′N, 124°12′E) and a pollen record from a nearby peat sequence are used for a detailed environmental reconstruction of the Holocene in the Lena Delta area. Shrubby Alnus fruticosa and Betula exilis tundra existed during 10,300–4800 cal. yr BP and gradually disappeared after that time. Climate reconstructions based on the pollen and chironomid records suggest that the climate during ca. 10,300–9200 cal. yr BP was up to 2–3 °C warmer than the present day. Pollen-based reconstructions show that the climate was relatively warm during 9200–6000 cal. yr BP and rather unstable between ca. 5800–3700 cal. yr BP. Both the qualitative interpretation of pollen data and the results of quantitative reconstruction indicate that climate and vegetation became similar to modern-day conditions after ca. 3600 cal. yr BP. The chironomid-based temperature reconstruction suggests a relatively warm period between ca. 2300 and 1400 cal. yr BP, which corresponds to the slightly warmer climate conditions reconstructed from the pollen. Modern chironomid and rhizopod assemblages were established after ca. 1400 cal. yr BP.

Description: Review is given about the main results of the oceanographic component of the BALTEX research programme (one of the six continental scale experiments within GEWEX-WCRP to study water and energy cycles in the regional climate system) and related programmes/projects over the last 10 years. Working closely together with two other components – regional meteorology and hydrology of the Baltic Sea drainage basin – oceanographic research has considerably improved the understanding of and ability to model the Baltic Sea marine system. In the Baltic Sea physics seven different broad topics are identified where knowledge has significantly improved. These are reviewed together with a discussion of gaps in knowledge. The focus is on the water and energy cycles of the Baltic Sea, but various aspects of forcing and validation data and modelling are also discussed. The major advances achieved through BALTEX and related programmes are: • Meteorological, hydrological, ocean and ice data are now available for the research community. • Progress in understanding of the strong impact of large-scale atmospheric circulation on Baltic Sea circulation, water mass exchange, sea ice evolution, and changes in the ocean conditions of the Baltic Sea. • Progress in understanding of the importance of strait flows in the exchange of water into and within the Baltic Sea. • Progress in understanding of intra-basin processes. • Ocean models introduced into Baltic Sea water and energy studies. • Development of turbulence models and 3D ocean circulation models for application to the Baltic Sea. • Improved Baltic Sea ice modelling and increased understanding of the need for coupled atmosphere–ice–ocean-land models.

Description: Most simple models for cooling of sheet like intrusions, the Hawaiian lava lakes being one example, neglect the effect of side wall heat loss on the overall thermal evolution. In this paper we extend a conventional one-dimensional (1D) model for cooling of sheet like intrusions to account for lateral heat loss by either prescribing a fixed side wall heat flux, or a heat flux controlled by heat transport in the surrounding wall rock. In the first part of the study we analyze the general interplay between side wall cooling and the thermal evolution of the system; the second part focuses on a comparison between our modeling results including models without and with lateral heat flux, and the Hawaiian lava lake data. This comparison leads to the following three main conclusions: (1) Side wall cooling does have a significant impact on the cooling history of lava lakes. (2) Models assuming a time dependent temperature profile in the wall rock lead to a better fit with the measured temperature data. (3) Due to the sluggish conductive heat transfer in the mush its thermal evolution is significantly decoupled from the temperature evolution of the convecting bulk liquid.

Description: The behavior of dissolved Hf in the marine environment is not well understood due to the lack of direct seawater measurements of Hf isotopes and the limited number of Hf isotope time-series obtained from ferromanganese crusts. In order to place better constraints on input sources and develop further applications, a combined Nd-Hf isotope time-series study of five Pacific ferromanganese crusts was carried out. The samples cover the past 38 Myr and their locations range from sites at the margin of the ocean to remote areas, sites from previously unstudied North and South Pacific areas, and water depths corresponding to deep and bottom waters. For most of the samples a broad coupling of Nd and Hf isotopes is observed. In the Equatorial Pacific εNd and εHf both decrease with water depth. Similarly, εNd and εHf both increase from the South to the North Pacific. These data indicate that the Hf isotopic composition is, in general terms, a suitable tracer for ocean circulation, since inflow and progressive admixture of bottom water is clearly identifiable. The time-series data indicate that inputs and outputs have been balanced throughout much of the late Cenozoic. A simple box model can constrain the relative importance of potential input sources to the North Pacific. Assuming steady state, the model implies significant contributions of radiogenic Nd and Hf from young circum-Pacific arcs and a subordinate role of dust inputs from the Asian continent for the dissolved Nd and Hf budget of the North Pacific. Some changes in ocean circulation that are clearly recognizable in Nd isotopes do not appear to be reflected by Hf isotopic compositions. At two locations within the Pacific Ocean a decoupling of Nd and Hf isotopes is found, indicating limited potential for Hf isotopes as a stand-alone oceanographic tracer and providing evidence of additional local processes that govern the Hf isotopic composition of deep water masses. In the case of the Southwest Pacific there is evidence that decoupling may have been the result of changes in weathering style related to the buildup of Antarctic glaciation.

Description: Hydrate Ridge, Cascadia convergent margin, is characterized by abundant methane hydrates at and below the seafloor, active venting of fluids and gases, chemosynthetic communities composed of giant sulfide-oxidizing bacteria and clams, authigenic carbonates, and some of the highest methane oxidation rates ever found in the marine environment. Fluid flow rates vary over six orders of magnitude among closely spaced settings at the crest of Hydrate Ridge. The distribution of benthic communities is mainly related to the sulfide flux from the subsurface sediments produced by anaerobic oxidation of methane (AOM). Even at high flux rates, AOM removes most of the methane seeping from the subsurface. Less than 50% of the methane escapes from bacterial mats, from Calyptogena fields 〈15%, and from Acharax beds, no methane is emitted to the water column. The precipitation of carbonate derived from AOM is a significant and permanent carbon sink. Hence, compared to the amount of gas hydrates and methane-derived carbonates stored at the summit of Hydrate Ridge, the emission of methane is relatively low due to the efficient filtering capacity of methanotrophic microbial communities. This present review updates current knowledge of the geology of Hydrate Ridge, summarizes recently published data on geomicrobiology and biogeochemistry, and derives a local methane budget.

Description: Understanding the hydrology of cold seep environments is crucial to perform accurate estimates of fluid and chemical fluxes at sedimentary wedges. Shallow convection processes may affect fluid flux estimates and could favor the destabilization of gas hydrate accumulations, increasing the sediment-ocean methane flux. Evidence for the occurrence of convection at cold seeps, however, is still limited. We use the concentration of 14C (D14C) in carbonate crusts formed at cold seeps of the eastern Mediterranean Sea as a tracer for convective recirculation of seawater-derived fluids. A numerical model is applied to investigate the controls on 14C incorporation in cold seep carbonates. Our simulations show that increased amounts of CH4 in the expelled fluids result in elevated crust D14C, while high Ca2+ and HCO3− concentrations produce the opposite effect. Convection is the only transport process that can significantly increase crust D14C. Advection, bioirrigation, eddy diffusion and bioturbation instead, have little effect on, or produce a decrease of, crust D14C. In addition, the presence of old or modern carbon (MC) in host sediments prior to cementation and the 14C-decay associated to the time needed to form the crust contribute in defining the D14C of carbonate crusts. We then use the model to reproduce the 14C content of the eastern Mediterranean Sea crusts to constrain the chemical and hydrological conditions that led to their formation. Some crusts contain relatively low amounts of 14C (−945.0〈D14C ‰〈−930.2) which, assuming no ageing after crust formation, can be reproduced without considering convection. Other crusts from two sites (the Amsterdam and Napoli mud volcanoes), instead, have a very high 14C-content (−899.0〈D14C ‰〈−838.4) which can only be reproduced by the model if convection mixes deep fluids with seawater. Order-of-magnitude calculations using the Rayleigh criterion for convection suggest that the slow seepage (about 10 cm year−1) of low salinity (20‰) fluids at the Amsterdam sites could trigger haline convection there. On the Napoli mud volcano, where high-density brines are expelled, density-driven convection cannot take place and other processes, possibly involving the rapid movement of free gas in the sediment, could be important.

Description: Here, we present a new technique for the direct measurement of 44Ca/40Ca isotope ratios on a Multicollector Inductively Coupled Plasma Mass Spectrometer (MC–ICP–MS, AXIOM) using the “cool plasma” technique. By reducing the plasma energy to about 400 W, the isobaric effect resulting from 40Ar+ can be significantly reduced, enabling the simultaneous and precise measurement of 44Ca and 40Ca beam intensities in different Faraday cups. In contrast to the TIMS technique requiring a 43Ca/48Ca double spike, the isotope measurements on MC–ICP–MS can be performed by bracketing standards. We express the calcium isotope variation relative to NIST SRM 915a (δ44/40Ca [‰]=[((44Ca/40Ca)sample/(44Ca/40Ca)NIST SRM 915a)−1]*1000). Isobaric effects of 24Mg16O+ and 23Na16OH+ interfering with 40Ca and 26Mg16OH2+ with 44Ca can be neglected by measuring calcium isotopes near the low-mass edge of the peaks. No influence of 87Sr2+ monitored on 43.5 atomic mass units (amu) was found. Repeated measurements of two Johnson Matthey CaCO3 standards (lot No. 4064 and lot No. 9912) revealed values of about −11.29 (‰ SRM 915a) and 0.57 (‰ SRM 915a). These values are in accordance with previous values published by Russell et al. [Geochim. Cosmochim. Acta 42 (1978) 1075], Heuser et al. [Int. J. Mass Spectrom. 220 (2002) 385], Hippler et al. [Geostand. Newsl. 27 (2003) 267] and Schmitt et al. [Geochim. Cosmochim. Acta 67 (2003) 2607]. Repeated measurement of the NIST SRM 915a CaCO3 standard showed that the variance of a single δ44/40Ca measurement is about 0.14‰ RSD being comparable with TIMS. MC–ICP–MS-based δ44/40Ca values measured on inorganically precipitated aragonite samples are indistinguishable from earlier measurements based on TIMS, confirming the positive correlation of δ44/40Ca and temperature. MC–ICP–MS-based δ44/40Ca measurements on cultured Orbulina universa showed a slope of about 0.026‰/°C being similar to the TIMS-based δ44/40Ca measurements showing a slope of about 0.019‰/°C. The large offset of about 5‰ between the two techniques is shown to be caused by a “matrix” effect, indicating that any δ44/40Ca measurements on MC–ICP–MS are sensitively controlled by the Ca concentration and the acidity of the solution. Our study demonstrates the possibility to measure the whole dispersion of calcium isotopes with MC–ICP–MS, showing that 40Ca can be used for normalization of 44Ca.

Description: Climate variability in the northeast Atlantic was investigated on glacial–interglacial and millennial time scales during the last 200 000 years, using sea surface temperature (SST) records derived from planktonic foraminiferal diversities and from Mg/Ca measurements on Globigerina bulloides. Paleoceanographical interpretations are supported by species composition analyses, benthic and planktonic isotopic data as well as records of iceberg-rafted debris (IRD). Differences of climate development are recognized for both interglacial and glacial periods. Temperature estimates indicate slightly warmer conditions (up to 2°C) during marine oxygen isotope stage (MIS) 5e than during the Holocene. In contrast to the last glaciation, when the SST minimum coincided with a minimum in solar insolation immediately before Termination I, during the penultimate glaciation a long SST minimum occurred at times of intermediate solar insolation well preceding the onset of Termination II. This discrepancy between two glacial terminations may be explained by an inherently different orbital configuration characteristic for each glacial interval. Despite these differences between the two glacial trends, the superimposed shorter-lived climatic events reveal the same order of principal steps, implying their common causal nature. A direct comparison of faunal SSTs with those retrieved from Mg/Ca analysis shows that Mg/Ca-derived temperatures follow the general glacial–interglacial trend; however, the latter appear to be largely overestimated. Supported by δ18O data in G. bulloides, which show little response to millennial-scale variability, there seems to be a need for species-dependent calibration experiments that also consider the different oceanographic settings this particular species can live in.

Description: In this paper, we summarize data on terrigenous sediment supply in the Kara Sea and its accumulation and spatial and temporal variability during Holocene times. Sedimentological, organic-geochemical, and micropaleontological proxies determined in surface sediments allow to characterize the modern (riverine) terrigenous sediment input. AMS-14C dated sediment cores from the Ob and Yenisei estuaries and the adjacent inner Kara Sea were investigated to determine the terrigenous sediment fluxes and their relationship to paleoenvironmental changes. The variability of sediment fluxes during Holocene times is related to the post-glacial sea-level rise and changes in river discharge and coastal erosion input. Whereas during the late/middle Holocene most of the terrigenous sediments were deposited in the estuaries and the areas directly off the estuaries, huge amounts of sediments accumulated on the Kara Sea shelf farther north during the early Holocene before about 9 Cal. kyr BP. The maximum accumulation at that time is related to the lowered sea level, increased coastal erosion, and increased river discharge. Based on sediment thickness charts, echograph profiles and sediment core data, we estimate an average Holocene (0–11 Cal. kyr BP) annual accumulation of 194×106 t yr−1 of total sediment for the whole Kara Sea. Based on late Holocene (modern) sediment accumulation in the estuaries, probably 12×106 t yr−1 of riverine suspended matter (i.e., about 30% of the input) may escape the marginal filter on a geological time scale and is transported onto the open Kara Sea shelf. The high-resolution magnetic susceptibility record of a Yenisei core suggests a short-term variability in Siberian climate and river discharge on a frequency of 300–700 yr. This variability may reflect natural cyclic climate variations to be seen in context with the interannual and interdecadal environmental changes recorded in the High Northern Latitudes over the last decades, such as the NAO/AO pattern. A major decrease in MS values starting near 2.5 Cal. kyr BP, being more pronounced during the last about 2 Cal. kyr BP, correlates with a cooling trend over Greenland as indicated in the GISP-2 Ice Core, extended sea-ice cover in the North Atlantic, and advances of glaciers in western Norway. Our still preliminary interpretation of the MS variability has to be proven by further MS records from additional cores as well as other high-resolution multi-proxy Arctic climate records.

Description: In the past decade, within the framework of joint Russian–German marine and terrestrial studies on the Arctic shelf, New Siberian Islands, and coastal lowlands of the Laptev and East Siberian seas, fundamentally new data have been obtained on terrestrial and offshore permafrost in this area. Field and laboratory investigations supplemented with numerical modeling and generalization of the results of numerous geological surveys, exploratory works, and scientific researches performed in previous years have made it possible to revise existing knowledge about the distribution, thickness, physical state, and history of development of terrestrial and offshore permafrost in the East Siberian part of the Arctic. The main results of these studies and their interpretation are discussed in this paper.

Description: This paper summarizes the results of studies of the Late Weichselian periglacial environments carried out in key areas of northern Eurasia by several QUEEN teams (European Science Foundation (ESF) programme: “Quaternary Environment of the Eurasian North”). The palaeoglaciological boundary conditions are defined by geological data on timing and extent of the last glaciation obtained in the course of the EU funded project “Eurasian Ice Sheets”. These data prove beyond any doubt, that with the exception of the northwestern fringe of the Taymyr Peninsula, the rest of the Eurasian mainland and Severnaya Zemlya were not affected by the Barents–Kara Sea Ice Sheet during the Last Glacial Maximum (LGM). Inversed modelling based on these results shows that a progressive cooling which started around 30 ka BP, caused ice growth in Scandinavia and the northwestern areas of the Barents–Kara Sea shelf, due to a maritime climate with relatively high precipitation along the western flank of the developing ice sheets. In the rest of the Eurasian Arctic extremely low precipitation rates (less than 50 mm yr−1), did not allow ice sheet growth in spite of the very cold temperatures. Palaeoclimatic and palaeoenvironmental conditions for the time prior to, during, and after the LGM have been reconstructed for the non-glaciated areas around the LGM ice sheet with the use of faunal and vegetation records, permafrost, eolian sediments, alluvial deposits and other evidences. The changing environment, from interstadial conditions around 30 ka BP to a much colder and drier environment at the culmination of the LGM at 20–15 ka BP, and the beginning of warming around 15 ka BP have been elaborated from the field data, which fits well with the modelling results.

Description: The bacterial community composition of the active layer (0–45 cm) of a permafrost-affected tundra soil was analysed by fluorescence in situ hybridisation (FISH). Arctic tundra soils contain large amounts of organic carbon, accumulated in thick soil layers and are known as a major sink of atmospheric CO2. These soils are totally frozen throughout the year and only a thin active layer is unfrozen and shows biological activity during the short summer. To improve the understanding of how the carbon fluxes in the active layer are controlled, detailed analysis of composition, functionality and interaction of soil microorganisms was done. The FISH analyses of the active layer showed large variations in absolute cell numbers and in the composition of the active microbial community between the different horizons, which is caused by the different environmental conditions (e.g., soil temperature, amount of organic matter, aeration) in this vertically structured ecosystem. Universal protein stain 5-(4,6-dichlorotriazin-2-yl)aminofluorescein (DTAF) showed an exponential decrease of total cell counts from the top to the bottom of the active layer (2.3 × 109–1.2 × 108 cells per gram dry soil). Using FISH, up to 59% of the DTAF-detected cells could be detected in the surface horizon, and up to 84% of these FISH-detected cells could be affiliated to a known phylogenetic group. The amount of FISH-detectable cells decreased with increasing depth and so did the diversity of ascertained phylogenetic groups.

Description: Testate amoebae (Protozoa: Testacea) were studied in the Late Quaternary permafrost deposits in the Siberian Arctic (Bykovsky Peninsula of the Laptev Sea coast, 71°40′ –71°80′ N and 129°–129°30′ E). The Testacea associations studied reflect specific environmental conditions in paleocryosols, which were controlled by the local micro-relief as well as by regional climate conditions. In total, 86 species, varieties, and forms of testate amoebae were found in 38 Pleistocene and Holocene samples. The rhizopods indicate that soil conditions at ca. 53,000 14C years BP were probably rather similar to the modern cold and wet arctic tundra environment. More moisture and warmer soil conditions were relatively favorable for rhizopods ca. 45,300–43,000 14C years BP, but it was significantly drier at about 42,000 14C years BP. Drier and colder environmental conditions were also present about 39,300–35,000 14C years BP. The Late Pleistocene samples, radiocarbon dated to 33,000–12,000 years BP, are characterized by a low species diversity and density indicating that this period may have been extremely cold and dry. This conjecture is also supported by the polymorphism of some species. Hydrophilic Difflugia species (mostly obligate hydrobiotes) are broadly represented in the studied Holocene samples. The species composition and density of rhizopods in the majority of Holocene samples suggest wet and relatively warm conditions. Changes in rhizopod assemblages during the last 53,000 years were not very dramatic, mostly consisting of rare species and changes in the dominant species complexes during the Pleistocene and Holocene. However, these changes were more drastic during the Pleistocene. They were probably at least partly responsible for the disappearance of some rare testacean species such as Argynnia sp.

Description: Horizontal gene transfer is an important mechanism for the evolution of microbial genomes. Pathogenicity islands — mobile genetic elements that contribute to rapid changes in virulence potential — are known to have contributed to genome evolution by horizontal gene transfer in many bacterial pathogens. Increasing evidence indicates that equivalent elements in non-pathogenic species — genomic islands — are important in the evolution of these bacteria, influencing traits such as antibiotic resistance, symbiosis and fitness, and adaptation in general. This review discusses the recent lessons that have been learned from pathogenicity islands in pathogenic microorganisms and how they apply to the role of genomic islands in commensal, symbiotic and environmental bacteria.

Description: In July 2001, samples of surface suspended particulate material (SPM) of the Irtysh river in its middle and lower reaches (from Omsk City to the confluence with the Ob river) and its main tributaries were collected (18 stations along 1834 km). The SPM samples were analyzed for major and trace element composition. The results show that the geochemistry of Irtysh river SPM is related to landscape and geochemical peculiarities of the river basin on one hand and to industrial activities within the drainage area on the other hand. In the upper basin polymetallic and cinnabar deposits and phosphorite deposits with high As content are widespread. The open-cut mining and developed oil-refining, power plants and other industries lead to the contamination of the environment by heavy metals and other contaminants. The territory of the West Siberian lowland, especially the Ob-Irtysh interfluve, is characterized by the occurrence of swamps and peat-bogs. Tributaries of the Irtysh river originating in this region, have a brown color and the chemical composition of the SPM is specific for stagnant water. In the first 500–700 km downstream from Omsk City the Irtysh river has the typical Al–Si-rich suspended matter composition. After the inflow of the tributaries with brown water the SPM composition is significantly changed: an increase of POC, Fe, P, Ca, Sr, Ba and As concentrations and a strong decrease of the lithogenic elements Al, Mg, K, Na, Ti, Zr can be observed. The data show that Fe-organic components (Fe-humic amorphous compounds, which contribute ca. 75–85% to the total Fe) play a very important role in SPM of the tributaries with brown water and in the Irtysh river in its lower reaches. Among the trace metals significant enrichments relative to the average for global river SPM could only be observed for As and Cd (coefficient of enrichment up to 16 for As and 3–3.5 for Cd). It can be shown that the enrichment of As in the SPM is related to natural processes, i.e. the weathering of phosphate containing deposits with high As concentrations in the upper Irtysh basin and the high As–P affinity in the swamp peaty soil. Dissolved P and As are absorbed by amorphous organic C/Fe oxyhydroxide components which act as carriers during the transport to the main stream of the Irtysh river. The role of anthropogenic factors is probably insignificant for As. In contrast, the enrichment of Cd is mainly related to anthropogenic input. The threefold enrichment of Cd in the SPM just below Omsk City and its continuous decrease down to background level at a distance of 500–700 km downstream points quite definitely to the municipal and industrial sewage of Omsk City as the main source of Cd in the SPM of the Irtysh river.

Description: The spatio-temporal pattern of peak Holocene warmth (Holocene thermal maximum, HTM) is traced over 140 sites across the Western Hemisphere of the Arctic (0–180°W; north of ∼60°N). Paleoclimate inferences based on a wide variety of proxy indicators provide clear evidence for warmer-than-present conditions at 120 of these sites. At the 16 terrestrial sites where quantitative estimates have been obtained, local HTM temperatures (primarily summer estimates) were on average 1.6±0.8°C higher than present (approximate average of the 20th century), but the warming was time-transgressive across the western Arctic. As the precession-driven summer insolation anomaly peaked 12–10 ka (thousands of calendar years ago), warming was concentrated in northwest North America, while cool conditions lingered in the northeast. Alaska and northwest Canada experienced the HTM between ca 11 and 9 ka, about 4000 yr prior to the HTM in northeast Canada. The delayed warming in Quebec and Labrador was linked to the residual Laurentide Ice Sheet, which chilled the region through its impact on surface energy balance and ocean circulation. The lingering ice also attests to the inherent asymmetry of atmospheric and oceanic circulation that predisposes the region to glaciation and modulates the pattern of climatic change. The spatial asymmetry of warming during the HTM resembles the pattern of warming observed in the Arctic over the last several decades. Although the two warmings are described at different temporal scales, and the HTM was additionally affected by the residual Laurentide ice, the similarities suggest there might be a preferred mode of variability in the atmospheric circulation that generates a recurrent pattern of warming under positive radiative forcing. Unlike the HTM, however, future warming will not be counterbalanced by the cooling effect of a residual North American ice sheet.

Description: Diatom assemblages and organic carbon records from two sediment cores located within an estuarian bay of the inner Kara Sea trace changes in Yenisei River runoff and postglacial depositional environments. Paleosalinity and sea-ice reconstructions are based on modern relationships of local diatom assemblages and summer surface-water salinity. Approximately 15,500 cal yr B.P., rivers and bogs characterized the study area. When sea level reached the 38- to 40-m paleo-isobath approximately 9300 cal yr B.P., the coring site was flooded. From 9300–9100 cal yr B.P., estuarine conditions occurred proximal to the depocenter of fluvially derived material, and salinity was 〈7–8. Paleosalinity increased to 11–13 by 7500 cal yr B.P., following postglacial sea-level rise and the southward shift of the Siberian coast. Sharp decreases in diatom accumulation rates, total sediment, and organic carbon also occurred, suggesting the presence of brackish conditions and greater distance between the coast and study site. Maximum paleosalinity (up to 13) was recorded between 7500 and 6000 cal yr B.P., which was likely caused by the enhanced penetration of Atlantic waters to the Kara Sea. Stepwise decreases to modern salinity levels happened over the last 6000 cal yr.

Description: Maintaining deep sea animals in in situ conditions has always been technically difficult because of the high-pressure requirements. Even more difficult are any attempts in manipulating or sampling these organisms while keeping them alive in high-pressure aquaria. We present a technique to withdraw blood samples by vascular catheterization which allows withdrawal of samples of during maintenance of specimens under high-pressure conditions. We have developed this technique to answer a long debated question, how carbon dioxide is transported from the ambient sea water to the bacterial symbionts inside the trophosome of the hydrothermal vent tubeworm Riftia pachyptila. Our results indicate that the carbon supply to the symbionts is mainly through inorganic CO2 while its incorporation into malate and succinate may serve storage functions at periods of low CO2 availability in the environment.

Description: Large uncertainties about the energy resource potential and role in global climate change of gas hydrates result from uncertainty about how much hydrate is contained in marine sediments. During Leg 204 of the Ocean Drilling Program (ODP) to the accretionary complex of the Cascadia subduction zone, we sampled the gas hydrate stability zone (GHSZ) from the seafloor to its base in contrasting geological settings defined by a 3D seismic survey. By integrating results from different methods, including several new techniques developed for Leg 204, we overcome the problem of spatial under-sampling inherent in robust methods traditionally used for estimating the hydrate content of cores and obtain a high-resolution, quantitative estimate of the total amount and spatial variability of gas hydrate in this structural system. We conclude that high gas hydrate content (30–40% of pore space or 20–26% of total volume) is restricted to the upper tens of meters below the seafloor near the summit of the structure, where vigorous fluid venting occurs. Elsewhere, the average gas hydrate content of the sediments in the gas hydrate stability zone is generally 〈2% of the pore space, although this estimate may increase by a factor of 2 when patchy zones of locally higher gas hydrate content are included in the calculation. These patchy zones are structurally and stratigraphically controlled, contain up to 20% hydrate in the pore space when averaged over zones ∼10 m thick, and may occur in up to ∼20% of the region imaged by 3D seismic data. This heterogeneous gas hydrate distribution is an important constraint on models of gas hydrate formation in marine sediments and the response of the sediments to tectonic and environmental change.

Description: Detrital zircon ages are commonly used to investigate sediment provenance and supply routes. Here, we explore the advantages of employing multiple, complimentary techniques via a case study of the Neoproterozoic and Cambrian of the Adelaide Rift Complex, South Australia. Detrital muscovite Ar–Ar ages are presented from stratigraphic units, or equivalents, that have previously been the subject of U–Pb detrital zircon dating, and, in some cases, whole-rock Sm–Nd isotope studies. The zircon age ranges and whole-rock Sm–Nd isotope data suggest that early Neoproterozoic sediments from near the base of the Adelaide Rift Complex comprise a mixture of detritus derived from the adjacent Gawler Craton (Palaeoproterozoic to earliest Mesoproterozoic) and overlying Gairdner flood basalts. In contrast, detrital muscovites from this level have a broad scatter of Mesoproterozoic infrared (IR) laser total fusion Ar–Ar ages, while UV laser traverses indicate that the age spread reflects partial resetting by multiple heating events, rather than a mixture of sources. Younger Neoproterozoic sediments document replacement of the Gawler Craton by the more distant Musgrave and/or Albany–Fraser Orogens as the main provenance. The Cambrian Kanmantoo Group marks an abrupt change in depositional style and a new sediment source. The Kanmantoo Group have older Nd model ages than underlying strata, yet are dominated by near to deposition-aged (∼500–650 Ma) detrital zircons and muscovites, suggesting rapid cooling and exhumation of a tectonically active provenance region. Although this source remains uncertain, evidence points towards the distant Pan-African orogenic belts. Deposition in the Adelaide Rift Complex was terminated in the late Early Cambrian by the Delamerian Orogeny, and the results of previous detrital mineral dating studies from the Lachlan Fold Belt to the east are consistent with at least partial derivation of these sediments from reworked upper Adelaide Rift Complex (Kanmantoo Group), rather than a continuation of sediment supply from the Kanmantoo Group sediment source. More broadly, the data suggest a close link between basin formation and orogen exhumation, and we also speculate that mantle plumes have played a significant role in crustal evolution at this Palaeo-Pacific margin of Gondwanaland, challenging the notion that subduction zones are the principle sites of crustal growth and sediment provenance.

Description: The existence in the ocean of deep western boundary currents, which connect the high-latitude regions where deep water is formed with upwelling regions as part of the global ocean circulation, was postulated more than 40 years ago1. These ocean currents have been found adjacent to the continental slopes of all ocean basins, and have core depths between 1,500 and 4,000 m. In the Atlantic Ocean, the deep western boundary current is estimated to carry (10–40) times 106 m3 s-1 of water2, 3, 4, 5, transporting North Atlantic Deep Water—from the overflow regions between Greenland and Scotland and from the Labrador Sea—into the South Atlantic and the Antarctic circumpolar current. Here we present direct velocity and water mass observations obtained in the period 2000 to 2003, as well as results from a numerical ocean circulation model, showing that the Atlantic deep western boundary current breaks up at 8° S. Southward of this latitude, the transport of North Atlantic Deep Water into the South Atlantic Ocean is accomplished by migrating eddies, rather than by a continuous flow. Our model simulation indicates that the deep western boundary current breaks up into eddies at the present intensity of meridional overturning circulation. For weaker overturning, continuation as a stable, laminar boundary flow seems possible.

Description: At many cold vent sites authigenic carbonates precipitate due to the release of carbonate alkalinity during the anaerobic oxidation of methane. Carbonate precipitation often induces the formation of massive crusts at the sediment surface or within surface sediments. The range of physical and biogeochemical conditions allowing for the formation of carbonate crusts is largely unknown so that the significance of these widespread manifestations of fluid flow is unclear. Here, we use numerical modeling to investigate the conditions that induce carbonate crust formation in the sediment and the effect of crust formation on sediment porosity and fluid flow rate. Starting with the conditions prevailing at a previously investigated reference site located on Hydrate Ridge, off Oregon, several parameters are systematically varied in a number of numerical experiments. These parameters include coefficients of bioturbation and bioirrigation, sedimentation rate, fluid flow velocity, methane concentration in the ascending vent fluids, and pH and saturation state at the sediment–water interface. The simulations show that carbonate crusts in the sediments only form if the fluids contain sufficient dissolved methane (〉50 mM) and if bioturbation coefficients are low (〈0.05 cm2 a−1). Moreover, high sedimentation rates (〉50 cm ka−1) inhibit crust formation. Bioirrigation induces a downward displacement of the precipitation zone and accelerates the formation of a solid crust. Crusts only form over a rather narrow range of upward fluid flow velocities (20–60 cm a−1), which is somewhat enlarged (up to 90 cm a−1) if the overlying bottom waters are supersaturated with respect to calcite. At higher flow rates, methane is rapidly exported into the water column so that methane oxidation and carbonate precipitation cannot proceed within the surface sediment. The formation of a several centimeters thick carbonate crust in surface sediments is typically completed after a few hundred years (100–500 a). Crust formation reduces the supply of methane to surface sediments which imposes a strong resistance against diffusive and advective methane transport. Therefore, rates of anaerobic methane oxidation and sulfide production are diminished and thus the density and metabolism of chemosynthetic biological communities is limited by crust formation. Due to the moderate flow rates and the slow diffusive transport, only very little methane escapes into the bottom water overlying carbonate-encrusted vent areas.

Description: A high-resolution early diagenetic model for the North Sea sediments has been coupled with a pelagic ecosystem model to quantify the three-dimensional processes in the coupled sediment–water system from the sea surface to a sediment depth of 11 cm focussing on the processes in the sediments of the North Sea. The pelagic ecosystem model ECOHAM1 simulates the 1986 phytoplankton dynamics considering circulation, temperature, nutrient availability in the water column and the resulting flux of particulate organic carbon (POC) onto the sediment. These seasonal and regional variable water column processes are considered as forcing for the early diagenetic model C. CANDI, which calculates the processes in the upper sediment column, represented by 14 dissolved and 6 solid species, resolved with 84 vertical levels. With the coupled model the daily benthic fluxes of POC, oxygen, nitrate, phosphate, and sulphate at the sediment–water interface for each of the 1158 horizontal cells covering the whole North Sea area has been determined. The simulations show the seasonal and regional variations in the pelagic and the sediment system. The coupled model reproduces very well measured oxygen and nitrate penetration depths at selected validation stations. A vertical section from Fair Isle into the German Bight in summer demonstrates high spatial phosphate variability in the water column and in the sediment. Observations on the sediment–water interface fluxes and of concentration distributions in the sediment are very sparse. The results of this high-resolution model allows the calculation of budgets at the sediment–water interface for the whole simulation area. The annual cumulated phosphate flux across the sediment–water interface exhibits strong fluxes concentrated in a narrow band off the continental coast in shallow waters over 40 mmol m−2 yr−1, whereas in the central North Sea fluxes are lower than 30 mmol m−2 yr−1. Simulated annual cycle of fluxes at the sediment–water interface at a position located in the central North Sea showed a phosphate flux shifted by 1 month compared to the organic matter flux, whereas the sulphate flux into the sediment showed an overall time lag of about 5 months.

Description: While the majority of research on ultraviolet radiation (UVR) has focused on UVR-induced changes in the productivity and abundance of single taxonomic groups, only a few field studies have considered the influence of ambient UVR on complete assemblages, in particular of the macrobenthos. Using cutoff filters, we followed the effects of three radiation treatments, (1) PAR+UVAR+UVBR, (2) PAR+UVAR, (3) PAR, on macrobenthic community structure at Luderitz, Namibia, SE Atlantic, for 3 months. Species composition, biomass, evenness, and species richness were not significantly affected by UVR. while the diversity IT of PAR+UVAR+UVBR-exposed communities was significantly lower compared to PAR treatments. However, this effect was only observed early in succession. Increased abundance of the red alga Ceramium sp. coincided with vanishing UVR effects on the community, suggesting a muted UVR microclimate under the Ceramium canopy. Our results demonstrate that UVR could neither decrease diversity persistently, nor affect any of the other tested community parameters. Single UVR-tolerant species may provide protective shading for UVR-sensitive species, thus buffering harmful UVR effects at the community level. Missing UVBR effects suggest a limited influence of ozone depletion on shallow water macrobenthic diversity. (C) 2003 Elsevier B.V. All rights reserved.

Description: The magmatic evolution of the Alboran region (westernmost Mediterranean) contains important clues for improving our understanding of the origin of Mediterranean-style back-arc basins and the desiccation of the Mediterranean Sea in the Messinian. We use new laser 40Ar/39Ar age and geochemical (major and trace element and O–Sr–Nd–Pb isotope) data from igneous rocks from southern Spain, the Alboran Sea and northern Morocco to reconstruct the magmatic evolution of the westernmost Mediterranean since the Eocene. Lower Oligocene dikes near Malaga (33.6±0.6 Ma) and Middle to Upper Miocene volcanic rocks from the Alboran Sea area (6.57±0.04 to 11.8±0.4 Ma) can be subdivided into two groups: (1) LREE-depleted (relative to N-MORB), primarily tholeiitic series, and (2) LREE-enriched, primarily calc-alkaline series volcanic rocks. Both groups are generally enriched in fluid-mobile elements (e.g. Rb, Th, U, K and Pb) relative to fluid-immobile elements (e.g. Nb, Ta, LREE). The LREE-depleted group has 143Nd/144Nd (0.5128–0.5130) isotope ratios similar to Atlantic MORB but higher 87Sr/86Sr (0.7046–0.7100). In contrast, the LREE-enriched group has less radiogenic Nd (0.5121–0.5126) and tend to more radiogenic Sr (0.7066–0.7205) isotopic composition. Pb isotope ratios are surprisingly uniform and have compositions similar to marine sediments. Analyses of mineral separates show that mafic melts with relatively low δ18O (5.6–7.2‰) had high 87Sr/86Sr (0.7048–0.7088), Δ7/4 (10.6–14.1) and Δ8/4 (40.0–49.3). Modeling of the trace elements and Sr–Nd–Pb–O isotopic compositions provides compelling evidence for the contamination of the mantle source with hydrous fluids/melts, which can be explained through subduction of oceanic lithosphere beneath the Alboran Basin but not through detachment/delamination of lithospheric mantle. We present a geodynamic model that reconstructs the Late Eocene to Quaternary evolution of the western Mediterranean through westward roll-back of subducted Tethys oceanic lithosphere. Slab roll-back resulted in a large-scale reorganization of the western Mediterranean paleogeography, causing the closure of marine gateways linking the Atlantic Ocean to the Mediterranean Sea. Isolation of the Mediterranean Sea led to its desiccation, causing the Messinian Salinity Crisis.

Description: The validity of predictions derived from the intermediate disturbance hypothesis (IDH) was tested in situ by manipulating mussel dominated Western Baltic fouling communities. Assemblages of two different successional stages, 3 and 12 months old, underwent a 3-month period of disturbance treatment in terms of various frequencies of emersion. Emersion frequency levels ranged from 1×15 to 48×15 min emersion day−1. The study on the 3-month-old communities was repeated in 2 subsequent study years. Species richness, evenness and diversity (Shannon index) were recorded to measure the effects of frequency treatments on community structure. The IDH was confirmed in the first year, when diversity was found to be a unimodal function of the applied emersion frequency gradient. Diversity–disturbance relationships were inverse unimodal or non-significant in the second year, which was true for both successional stages. This ambiguous picture partially confirms the validity of the mechanisms proposed by the IDH, but also shows that their forcing can be masked by fluctuations in environmental parameters, such as climatic conditions. Diversity increased again under severe disturbance conditions, due to a disturbance-induced change in community structure, namely the shift from mussel to algal dominance. This is a new aspect in the discussion concerning disturbance–diversity relationships

Description: Biogenic structures in Late Quaternary sediments from the southwestern Iberian continental slope were studied by using X-ray images from two cores from 580 and 1750 m water depth. Eight different ichnocoenoses were observed: indistinct bioturbation, Planolites-dominated, Thalassinoides-dominated, Chondrites-dominated, Planolites and Thalassinoides-dominated, pyritized microburrows such as Trichichnus and ‘Mycellia’-dominated, Chondrites, Trichichnus, and ‘Mycellia’-dominated and Zoophycos. Variations of the ichnocoenoses within the cores show a striking correlation with climatically induced changes in the hydrographical regime, i.e. current strength and bathymetric position of the Mediterranean Outflow Water (MOW). Comparison of the response of the ichnocoenoses to changes in bottom-water conditions and substrate between the two cores studied indicate that bottom-water oxygenation and enrichment of particulate organic matter at the base of the MOW layer are the primary factors controlling the ichnocoenoses. The traces even recorded short-term climatic changes such as the Younger Dryas cold event. The spatial and temporal distribution patterns are in good agreement with earlier models of the MOW history, which gives reason to see a refinement of trace fossils as a complementary tool for paleoceanographical studies.

Description: We have analyzed the stable oxygen isotopic composition of two Porites corals from the Chagos Archipelago, which is situated in the geographical center of the Indian Ocean. Coral δ18O at this site reliably records temporal variations in precipitation associated with the Intertropical Convergence Zone (ITCZ). Precipitation maxima occur in boreal winter, when the ITCZ forms a narrow band across the Indian Ocean. The Chagos then lies within the center of the ITCZ, and rainfall is strongly depleted in δ18O. A 120-yr coral isotopic record indicates an alternation of wet and dry intervals lasting 15 to 20 yr. The most recent 2 decades are dominated by interannual variability, which is tightly coupled to the El Niño–Southern Oscillation (ENSO). This is unprecedented in the 120 yr of coral record. As the ITCZ is governed by atmospheric dynamics, this provides evidence of a major change in the coupled ENSO–monsoon system.

Description: The δ18O values of planktonic foraminifera increased in the Caribbean by about 0.5‰ relative to the equatorial East Pacific values between 4.6 and 4.2 Ma as a consequence of the closure of the Central American Gateway (CAG). This increase in δ18O can be interpreted either as an increase in Caribbean sea surface (mixed layer) salinity (SSS) or as a decrease in sea surface temperatures (SST). This problem represents an ideal situation to apply the recently developed paleotemperature proxy δ44/40Ca together with Mg/Ca and δ18O on the planktic foraminifer Globigerinoides sacculifer from ODP Site 999. Although differences in absolute temperature calibration of δ44/40Ca and Mg/Ca exist, the general pattern is similar indicating a SST decrease of about 2–3 °C between 4.4 and 4.3 Ma followed by an increase in the same order of magnitude between 4.3 and 4.0 Ma. Correcting the δ18O record for this temperature change and assuming that changes in global ice volume are negligible, the salinity-induced planktonic δ18O signal decreased by about 0.4‰ between 4.4 and 4.3 Ma and increased by about 0.9‰ between 4.3 and 4.0 Ma in the Caribbean. The observed temperature and salinity trends are interpreted to reflect the restricted exchange of surface water between the Caribbean and the Pacific in response to the shoaling of the Panamanian Seaway, possibly accompanied by a southward shift of the Intertropical Convergence Zone (ITCZ) between 4.4 and 4.3 Ma. Differences in Mg/Ca- and δ44/40Ca-derived temperatures can be reconciled by corrections for secular variations of the marine Mg/Casw and δ44/40Ca, a salinity effect on the Mg/Ca ratio and a constant temperature offset of ∼2.5 °C between both SST proxy calibrations.

Description: Halogenated transient tracers such as the chlorofluorocarbons CFC-11, CFC-12 and CFC-113 are commonly used in oceanographic studies. These compounds enter the ocean via the atmosphere and their transient atmospheric concentrations make them valuable as oceanic tracers. The trends of rapidly rising atmospheric concentrations of these tracers are however broken, and the oceanic signal becomes increasingly more difficult to decipher. There is a need for a new transient tracer to complement the existing suit of tracers, especially for recently ventilated water masses. One compound that looks promising in this respect is sulphur hexafluoride (SF6), an inert gas whose atmospheric concentration is rising rapidly. In this paper, the use of SF6 as a transient tracer in recently ventilated waters is discussed and the method for determination of SF6 in seawater is described. Tracer data from a section in the Atlantic sector of the Southern Ocean along 6°E, from 60°S to 40°S, occupied during January 1998, are presented. The Antarctic Polar Front, found close to 50°S, was studied with a densely sampled section down to 400 m depth and SF6/CFC-12 ratios are used to deduce ventilation ages and dilution factors. A comparison of apparent ages derived from a variety of tracers is presented together with the uncertainties in these estimates. This work demonstrates that SF6 is a useful and valuable transient tracer for waters ventilated during the last 20 years

Description: Effects of two presumably dominant competitors, the blue mussel Mytilus edulis and the barnacle Balanus improvisus on recruitment, population dynamics and community structure on hard substrata were experimentally investigated in the subtidal Kiel Fjord, Western Baltic. The hypothesis that blue mussels and/or barnacles are local dominants and strongly influence succession and community structure was tested by monitoring succession in the presence and absence of simulated predation on either or both species. Manipulations included blue mussel removal, barnacle removal, combined blue mussel and barnacle removal, as well as a control treatment for natural (non-manipulated) succession. In the second part of the experiment, recovery from the treatments was monitored over 1 year. During the manipulative phase of the experiment, blue mussels had a negative effect on recruitment of species, whereas barnacles had no significant effect. Even so, a negative synergistic effect of blue mussels and barnacles was detected. Calculation of species richness and diversity H-1 (Shannon Index) showed a negative synergistic effect of blue mussels and barnacles on community structure. Additionally, diversity H-1 was negatively affected by the dominant competitor M. edulis. These effects were also detectable in the ANOSIM-Analysis. The non-manipulative phase of the experiment brought about a drastic loss of diversity and species richness. Blue mussels dominated all four communities. Barnacles were the only other species still being able to coexist with mussels. Effects of simulated predation disappeared fast. Thus, in the absence of predation on blue mussels, M. edulis within a few months dominates available space, and diversity of the benthic community is low. In contrast, when mussel dominance is controlled by specific predators, more species may persist and diversity remains high

Description: Slope failure along the Costa Rica convergent margin commonly results from steepening of the continental slope above underthrust relief on the subducting plate. The 50-km-wide prehistoric Nicoya Slump was a big event that was followed by small slides from its headwall. Estimated maximum wave height above the slide is 27 m. The headwall occurs along a tectonized and unstable zone that extends northwest. An expected great earthquake in the adjacent Nicoya seismic gap could trigger future tsunamigenic landslides along this zone. The central Nicaragua slope, where the 1992 tsunamigenic earthquake occurred, has failed from steepening by tectonic erosion and perhaps subducting relief. The steep middle slope displays several large slide scars, each of which had the potential to generate a 6–7-m-high wave. A relation between the youngest slide and the 1992 earthquake is uncertain. Principal causes of landslides off Middle America were tectonic steepening and elevated fluid pressure. A mid-slope tectonized zone off Costa Rica allowed detachment of a huge slump involving the entire lower slope to the plate boundary. It may pose a hazard during rupture of the Nicoya locked zone.

Description: Holocene Pelado, Guespalapa and Chichinautzin monogenetic scoria cones and associated lava flows located within the Sierra del Chichinautzin Volcanic Field (SCVF) at the southern margin of Mexico City were mapped and sampled for mineralogical and chemical analyses. With the exception of Parı́cutin volcano in western Mexico, few scoria cones in the Trans-Mexican Volcanic Belt have ever been sampled in greater detail. Chemical analyses of rocks indicate that mafic products (e.g. Guespalapa and Chichinautzin) from individual volcanoes in the Sierra del Chichinautzin are characterized by substantial chemical variability, whereas high-silica andesite volcanoes (e.g. Pelado) are very uniform in composition. These findings have important bearings for regional tephrochronology. As a whole, rock compositions form a continuous coherent calc–alkaline suite, explicable by polybaric fractional crystallization±assimilation associated with successive stagnation at different depths along the ascent path. Trace element and Sr–Nd isotope analyses point toward a 〈1-km-scale heterogeneous (enriched/depleted) mantle wedge underneath the SCVF. The recently proposed plume-origin for these rocks is not in accord with our data. Instead, magma origin is discussed in relation to the tectonically complex subduction process of the oceanic Cocos Plate underneath the continental North American Plate.

Description: The climate of the last glacial period was extremely variable, characterized by abrupt warming events in the Northern Hemisphere, accompanied by slower temperature changes in Antarctica and variations of global sea level. It is generally accepted that this millennial-scale climate variability was caused by abrupt changes in the ocean thermohaline circulation. Here we use a coupled ocean–atmosphere–sea ice model to show that freshwater discharge into the North Atlantic Ocean, in addition to a reduction of the thermohaline circulation, has a direct effect on Southern Ocean temperature. The related anomalous oceanic southward heat transport arises from a zonal density gradient in the subtropical North Atlantic caused by a fast wave-adjustment process. We present an extended and quantitative bipolar seesaw concept that explains the timing and amplitude of Greenland and Antarctic temperature changes, the slow changes in Antarctic temperature and its similarity to sea level, as well as a possible time lag of sea level with respect to Antarctic temperature during Marine Isotope Stage 3.

Description: Nabukelevu volcano (805 m) is a small (ca. 3.4 km3) hornblende/biotite–andesite dome–breccia complex. It is the youngest in a Plio–Pleistocene series of volcanoes related to a presently inactive subduction zone in southern Fiji. We present new evidence of up to four Holocene eruption episodes from this volcano, with onshore evidence of the latest activity post-1686±40 years BP, and offshore evidence of tephra falls between 2250±70 and 780±50 years BP. Scoriaceous pyroclastic flow deposits of one eruptive episode contain pottery fragments, presumably entrained from habitation areas during emplacement. Like many composite edifices in moist climates, Nabukelevu is prone to failure, the propensity in this case exacerbated by up to three edifice-cutting fault zones. The fault-induced weak and saturated zones have been the focus of repeated edifice failure through late Holocene debris avalanches of between 10–100 million m3. Many of these avalanches entered the sea, and these or additional submarine failures of the lower island flanks have led to emplacement of at least one major late Holocene submarine mass-flow deposit with distinctive mineralogy in the Suva Basin to the north. Two of the debris avalanches dated at post-2350±140 and post-1750±60 years BP apparently inundated local habitation areas, and the deposits incorporate pottery and human remains. A widespread local legend describing catastrophic events on Nabukelevu corresponds in content with geologic findings to provide additional evidence of a late Holocene eruptive and debris avalanche disaster on Kadavu during the latter part of the last ca. 2000 years of human occupation, possibly as recent as between AD 1630 and 1680. The present hazardscape of the Nabukelevu area includes common landslides induced by frequent earthquake swarms and cyclones. Larger edifice failures, possibly related to volcanism or fault movement, have the potential to create local tsunami, which under favourable conditions could reach areas near Fiji’s capital, Suva, 110 km to the north.