ALBERT

Description: This chapter aims at introducing the reader to general concepts about the main forcings of the Mediterranean Sea, in terms of exchanges through the Strait of Gibraltar, and air-sea exchanges of heat, freshwater, and momentum. These forcings are also responsible for the peculiar characteristics of Mediterranean water masses. Therefore, the chapter continues with giving a general explanation on water mass analysis, and then it describes the properties and vertical and horizontal distributions of the main Mediterranean water masses. To conclude, the reader is introduced to the use of other (biogeochemical, and chemical) tracers of water masses, with a focus on the Mediterranean Sea.

Description: Wildfires are natural or anthropogenic phenomena increasing at alarming rates globally due to land-use alterations, droughts, climatic warming, hunting and biological invasions. Whereas wildfire effects on terrestrial ecosystems are marked and relatively well-studied, ash depositions into aquatic ecosystems have often remained overlooked but have the potential to significantly impact bottom-up processes. This study assessed ash-water-phytoplankton biomass dynamics using six plant species [i.e., three natives (apple leaf Philenoptera violacea, Transvaal milk plum Englerophytum magalismontanum, quinine tree Rauvolfia caffra) and three aliens (lantana Lantana camara, gum Eucalyptus camaldulensis, guava Psidium guajava)] based on a six-week mesocosm experiment with different ash concentrations (1 and 2 g L-1). We assessed concentrations of chemical elements, i.e., N, P, K, Ca, Mg, Na, Mn, Fe, Cu, Zn and B from ash collected, and we have observed significant differences among the species. High concentrations of P, K, Mn, Fe, Cu, Zn and B were recorded from Transvaal milk plum ash and low concentrations of P, K, Ca, Mg, Cu and Zn were recorded from apple leaf. An increase in phytoplankton biomass (using chlorophyll-a concentration as a proxy) for all treatments i.e., 1 and 2 g L-1 for all plant species ash was observed a week after, followed by decreases in the following weeks, with the exception of 2 g L-1 for lantana, gum and control. Silicate concentrations (i.e., used as a proxy for diatom abundance) showed increasing patterns among all ash treatments, with exception of controls. However, no clear patterns were observed between native and alien plant ash on both chl-a and silicate concentrations. We found that ash has notable effects on water chemistry, particularly nitrate, which increased throughout the weeks, whereas, pH and conductivity were high at low ash concentrations. The impacts of ash on water chemistry, chl-a and silicate concentrations vary with individual species and the amount of ash deposited into the system.

Description: Phytoplankton form the base of the pelagic food web in inland waters. Unlike rooted plants with access to nutrients in the sediment, phytoplankton depend on the open water as their sole direct source of minerals. Phytoplankton comprise cyanobacteria and phylogenetically diverse eukaryotic algae that convert light energy and mineral nutrients into organic matter. Many species also exploit the elements and energy within dissolved organic compounds and particles produced in the catchment or within the water. Here, we describe the nutrient requirements of phytoplankton, their different modes of nutrition, the mechanisms they employ to acquire nutrients and the ecological consequences of their varying ability to exploit an often scarce and spatially and temporally variable resource. When nutrients are abundant, often as a result of human disruption of nutrient cycles, phytoplankton productivity, and often biomass, increases to the point that it causes a range of ecological consequences that reduce the value of the water resource for mankind.

Description: Quantification of phthalates or phthalic acid esters (PAEs) might be problematic due to matrix overlap, auto-self absorbance and background scattering noise by the plastic lab materials although plastics have been reported in the release of PAEs. These materials (ambient air, reagents bottles, sampling devices, and various analytical instruments), are ubiquitous in the laboratory environment, thereby making it more difficult to reliably analyze of trace concentration of PAEs. Thus, in the current study, a straight forward and reliable protocol has been established for the analysis of PAEs including control of blank contamination, and the experimental conditions such as extraction time and temperature were optimized. The mass of PAEs in blank tests of selected materials ranged from 3±0.7 to 35±6 ng for liquid-liquid extraction (LLE) and from 5±1.8 to 63±15 ng for solid-phase extraction (SPE). For both extraction methods, higher blank values were measured for dibutyl phthalate (DBP) (35±6 ng, 12±3 ng), and DEHP (63±12 ng, 23±5 ng) in LLE and SPE, respectively. Average recoveries of PAEs in LLE were 90-97% and obtained with successive aliquots of 2 mL, 1 mL, and 1 mL dichloromethane (DCM). For SPE, recoveries up to 86-90% were achieved with successive aliquots of 5, 3, and 2 mL DCM at a sample flow rate of 5 mL min -1 . Under the optimized conditions, the method quantification limits (MQL) for PAEs was 10-20 ng L -1 for LLE and 10-35 ng L -1 for SPE. Moreover, the dissolved concentrations of PAEs from LDPE measured by the LLE method ranged 〈 1.5 to 5.83 ng cm -2, and those measured by SPE ranged from 1.0to256ngL -1 , in seawater samples of Sharm Obhur. The method has lower MQL values for LLE and SPE than average reported values of 10-100 ng L -1 and 30-100 ng L -1 , respectively.

Description: A key requirement for geological CO2 storage is site integrity management and monitoring during operation through to the post decommissioning period. This paper focuses on monitoring deformation of the ground surface and seabed as a proxy for overall deformation in the reservoir and surrounding layers. The objective is to inform, based on deformation data, on how the reservoir is responding to CO2 injection and to ensure any issues with regard to storage integrity are rapidly detected. The magnitude and pattern of deformation at the surface reveals geomechanical/hydromechanical processes that occur in reservoir due to CO2 injection. We acquired deformation data from the In Salah CO2 injection site and from four additional study cases during the course of this study; one in the onshore UK, the other a combined campaign onshore Norway and offshore Germany, and the third in onshore Japan. Significant developments in measurement techniques, processing tools and interpretation algorithms were developed through this project. Models were then developed to simulate the observed data and to couple surface deformation to displacement in the subsurface. The results show millimeter-scale deformations in the subsurface have a signature at the surface that can be captured by the tools and workflows developed in this project. These deformations, particularly the patterns, are important factors to consider when monitoring a CO2 storage site.

Description: The oceans' role in climate and climate change is manifold. The Ocean circulation transports large amounts of heat and freshwater on hemispheric space scales which have significant impacts on regional climate in the ocean itself but also noticeable consequences via atmospheric teleconnections on land. Due to the high heat capacity of seawater and the relatively slow ocean circulation, the oceans provide a significant “memory” for the climate system. Bodies of water that descend from the sea surface may reside in the ocean interior for decades and centuries, while preserving their temperature and salinity signature, before they surface again to interact with the overlying atmosphere. The residence time of water in the atmosphere is about ten days and the persistence of dynamical states of the atmospheric circulation may last up to a few weeks. Thus, on long time scales ocean dynamics becomes important for climate, which implies that climate variations and climate change can only partially be understood without consideration of ocean dynamics and the intricate ocean-atmosphere interaction. Since 1960 the heat uptake of the oceans has been 20 times larger than that of the atmosphere. Thus the oceans have been able to reduce the otherwise much more pronounced temperature rise in the atmospheric climate. Also, over the last 200 years the oceans have absorbed about half of the CO2 release into the atmosphere by human activities (fossil fuel combustion, de-forestation, cement production), thereby reducing the direct effect of greenhouse gases on atmospheric temperatures.This chapter aims to describe and explain fundamental principles of the ocean dynamics and gathers information about past, present and future states the world’s ocean and its role in climate change.

Description: Highlights • Continuous CH4 bioelectrosynthesis from CO2 demonstrated with 80% or higher Coulombic Efficiency • At pH values below 8 CH4 cathodic off-gas contains up to 85% CH4 • At pH above 8.5, production of acetate and then ethanol (up to 8 g L−1) was obtained • Coulombic efficiency remained above 80% • 16S sequencing showed proliferation of Clostridium, Methanosaeta, Methanobrevibacter and Methanobacterium spp at the cathode This study demonstrates the continuous conversion of CO2 to methane, acetate, and ethanol in a Microbial Electrosynthesis Cell (MESC) with a carbon felt biocathode. The MESC was inoculated with a mixed anaerobic microbial consortium and operated at a mesophilic temperature of 30 °C. In situ deposition of Ni and Fe was achieved by introducing 0.2 g L−1 of NiSO4 or FeSO4, respectively, into the cathode compartment influent stream. In response, a considerable improvement in MESC performance was observed with a current density of 6.4 mA cm−2 (per separator area) and a CH4 production of 0.83 L (LR d)−1 (R = cathode volume). Once Ni and Fe were removed from the influent solution, the performance remained unchanged. Electron dispersive spectroscopy confirmed Ni and Fe electrodeposition. A shift from CH4 to acetate and ethanol production with concentrations reaching 5 and 8 g L−1, respectively, was observed upon increasing the cathode compartment pH to 8.5–9.0. 16S rRNA gene sequencing showed significant changes in the bacterial population at the cathode with Clostridia representing almost two-thirds of the population. Methanosaeta, Methanobrevibacter, and Methanobacterium species dominated the archaeal community.

Description: Rivers are viewed as major pathways of microplastic transport from terrestrial areas to marine ecosystems. However, there is paucity of knowledge on the dispersal pattern and transport of microplastics in river sediments. In this study, a three dimensional hydrodynamic and particle transport modelling framework was created to investigate the dispersal and transport processes of microplastic particles commonly present in the environment, namely, polyethylene (PE), polypropylene (PP), polyamide (PA), and polyethylene terephthalate (PET) in river sediments. The study outcomes confirmed that sedimental microplastics with lower density would have higher mobility. PE and PP are likely to be transported for a relatively longer distance, while PA and PET would likely accumulate close to source points. High water flow would transport more microplastics from source points, and high flow velocity in bottom water layer are suggested to facilitate the transport of sedimental microplastics. Considering the limited dispersal and transport, the study outcomes indicated that river sediments would act as a sink for microplastic pollutants instead of being a transport pathway. The patchiness associated with the hotspots of different plastic types is expected to provide valuable information for microplastic source tracking.

Description: Microbially catalyzed corrosion of metals is a substantial economic concern. Aerobic microbes primarily enhance Fe0 oxidation through indirect mechanisms and their impact appears to be limited compared to anaerobic microbes. Several anaerobic mechanisms are known to accelerate Fe0 oxidation. Microbes can consume H2 abiotically generated from the oxidation of Fe0. Microbial H2 removal makes continued Fe0 oxidation more thermodynamically favorable. Extracellular hydrogenases further accelerate Fe0 oxidation. Organic electron shuttles such as flavins, phenazines, and possibly humic substances may replace H2 as the electron carrier between Fe0 and cells. Direct Fe0-to-microbe electron transfer is also possible. Which of these anaerobic mechanisms predominates in model pure culture isolates is typically poorly documented because of a lack of functional genetic studies. Microbial mechanisms for Fe0 oxidation may also apply to some other metals. An ultimate goal of microbial metal corrosion research is to develop molecular tools to diagnose the occurrence, mechanisms, and rates of metal corrosion to guide the implementation of the most effective mitigation strategies. A systems biology approach that includes innovative isolation and characterization methods, as well as functional genomic investigations, will be required in order to identify the diagnostic features to be gleaned from meta-omic analysis of corroding materials. A better understanding of microbial metal corrosion mechanisms is expected to lead to new corrosion mitigation strategies. The understanding of the corrosion microbiome is clearly in its infancy, but interdisciplinary electrochemical, microbiological, and molecular tools are available to make rapid progress in this field.

Description: Highlights: • Transcriptional response to hypoxia-reoxygenation was studied in an OMZ bivalve. • Anaerobic glycolysis and protein quality control pathways were transcriptionally upregulated in hypoxia. • Hypoxia elevated mRNA levels of UCP2 but had no effect on thiol-dependent antioxidants. • No impact of hypoxia-reoxygenation was found on aerobic marker enzymes. • Responses of an OMZ bivalve show parallels to other hypoxia-tolerant bivalves. Abstract: Benthic animals inhabiting the edges of marine oxygen minimum zones (OMZ) are exposed to unpredictable large fluctuations of oxygen levels. Sessile organisms including bivalves must depend on physiological adaptations to withstand these conditions. However, as habitats are rather inaccessible, physiological adaptations of the OMZ margin inhabitants to oxygen fluctuations are not well understood. We therefore investigated the transcriptional responses of selected key genes involved in energy metabolism and stress protection in a dominant benthic species of the northern edge of the Namibian OMZ, the nuculanid clam Lembulus bicuspidatus,. We exposed clams to normoxia (~5.8 ml O2 l−1), severe hypoxia (36 h at ~0.01 ml O2 l−1) and post-hypoxic recovery (24 h of normoxia following 36 h of severe hypoxia). Using newly identified gene sequences, we determined the transcriptional responses to hypoxia and reoxygenation of the mitochondrial aerobic energy metabolism (pyruvate dehydrogenase E1 complex, cytochrome c oxidase, citrate synthase, and adenine nucleotide translocator), anaerobic glycolysis (hexokinase (HK), phosphoenolpyruvate carboxykinase (PEPCK), phosphofructokinase, and aldolase), mitochondrial antioxidants (glutaredoxin, peroxiredoxin, and uncoupling protein UCP2) and stress protection mechanisms (a molecular chaperone HSP70 and a mitochondrial quality control protein MIEAP) in the gills and the labial palps of L. bicuspidatus. Exposure to severe hypoxia transcriptionally stimulated anaerobic glycolysis (including HK and PEPCK), antioxidant protection (UCP2), and quality control mechanisms (HSP70 and MIEAP) in the gills of L. bicuspidatus. Unlike UCP2, mRNA levels of the thiol-dependent mitochondrial antioxidants were not affected by hypoxia-reoxygenation stress. Transcript levels of marker genes for aerobic energy metabolism were not responsive to oxygen fluctuations in L. bicuspidatus. Our findings highlight the probable importance of anaerobic succinate production (via PEPCK) and mitochondrial and proteome quality control mechanisms in responses to oxygen fluctuations of the OMZ bivalve L. bicuspidatus. The reaction of L. bicuspidatus to oxygen fluctuations implies parallels to that of other hypoxia-tolerant bivalves, such as intertidal species.

Description: During 2 sampling campaigns single valves of a minute species of Polititapes were dredged at 26–42 m depths off the northern coast of Namibia. The shells were found in muddy and silty sediment with a high diversity of benthic life. Polititapes parvovalis sp. nov. differs from all known West and South African Veneridae and is described as new. Because of the indistinct lunule, we have assigned the new species to the genus Polititapes with reservations.

Description: Despite the growing concern of scyphozoan jellyfish blooms and their associated threats, there is an acute lack of baseline knowledge regarding the trophic ecology of scyphozoans in tropical waters where blooms of several species sometimes occur at once or successively. Therefore, this study was conducted from June 2010 to December 2011 in the Klang Strait (Malaysia) to elucidate the trophic ecology of eight sympatric species of scyphozoan that occurred in a conjoint mangrove-mudflat habitat. The species diet, trophic position and the relative contribution of primary producers to their nutrition were determined by integrating stomach content examination with stable isotope analysis. Scyphozoans in the Klang Strait are principally carnivores and can be grouped into three major trophic guilds: specialized copepod feeder, copepod and macrozooplankton feeder, and mixed plankton feeder. Bayesian mixing model of δ13C isotope values indicates that the scyphozoans mainly derived their basal carbon source from microphytobenthos and phytoplankton. Analysis of δ15N isotope values reveals that all species are positioned at the third trophic level after mixed zooplankton groups (second) and primary producers (first) in the food web. Scyphozoans thus represent an important trophic link coupling benthic and pelagic primary production to higher-level predators and humans, and are important carbon exporters from nearshore to neritic and offshore waters.

Description: Being integral primary producers in diverse ecosystems, microalgal genomes could be mined for ecological insights, but representative genome sequences are lacking for many phyla. We cultured and sequenced 107 microalgae species from 11 different phyla indigenous to varied geographies and climates. This collection was used to resolve genomic differences between saltwater and freshwater microalgae. Freshwater species showed domain-centric ontology enrichment for nuclear and nuclear membrane functions, while saltwater species were enriched in organellar and cellular membrane functions. Further, marine species contained significantly more viral families in their genomes (p = 8e–4). Sequences from Chlorovirus, Coccolithovirus, Pandoravirus, Marseillevirus, Tupanvirus, and other viruses were found integrated into the genomes of algal from marine environments. These viral-origin sequences were found to be expressed and code for a wide variety of functions. Together, this study comprehensively defines the expanse of protein-coding and viral elements in microalgal genomes and posits a unified adaptive strategy for algal halotolerance.

Description: A major highlight of restoration efforts is to improve the ecological structure and function of the natural ecosystem in the restored habitat. Assessment of restoration success is a crucial component of an optimal ecological management strategy. In studies to determine the restoration success of a transplanted seagrass habitat by assessing trophic recovery, we examined carbon and nitrogen stable isotope ratios of organic matter sources and macrobenthic assemblages in a transplanted eelgrass Zostera marina bed. The eelgrass bed was restored about 2 years after transplantation in a southern coastal bay of Korea, and consequently, the food web structure in the bed was compared with that in a natural reference site. Our results revealed no significant differences in isotopic values of both macrobenthic consumers and their putative food sources between the transplanted and natural seagrass beds. These isotopic similarities in florae and faunae in the two beds suggest a uniformity in food web structure formed by the diversity and availability of resources, and thereby suggest similarities in the resource–consumer relationship. Isotopic niche indices and high dietary overlaps of feeding guilds in the transplanted and natural beds further suggest the transplanted habitat provides similar ecological functions and ecosystem services to its natural counterpart. Collectively, our results suggest the eelgrass transplantation led to successful restoration of a common seagrass bed, with recovery of the functional properties of the food web structure. Finally, our findings support the idea that stable isotope measures can provide a better understanding of the functioning of restored ecosystems, and improve post-transplantation monitoring efforts for the future planning and managing of successful habitat restoration.

Description: Micro- and nano-scale plastic particles in the environment result from their direct release and degradation of larger plastic debris. Relative to macro-sized plastics, these small particles are of special concern due to their potential impact on marine, freshwater, and terrestrial systems. While microplastic (MP) pollution has been widely studied in geographic regions globally, many questions remain about its origins. It is assumed that urban environments are the main contributors but systematic studies are lacking. The absence of standard methods to characterize and quantify MPs and smaller particles in environmental and biological matrices has hindered progress in understanding their geographic origins and sources, distribution, and impact. Hence, the development and standardization of methods is needed to establish the potential environmental and human health risks. In this study, we investigated stable carbon isotope ratio mass spectrometry (IRMS), attenuated total reflectance - Fourier transform infrared (ATR-FTIR) spectroscopy, and micro-Raman spectroscopy (μ-Raman) as complementary techniques for characterization of common plastics. Plastic items selected for comparative analysis included food packaging, containers, straws, and polymer pellets. The ability of IRMS to distinguish weathered samples was also investigated using the simulated weathering conditions of ultraviolet (UV) light and heat. Our IRMS results show a difference between the δ13C values for plant-derived and petroleum-based polymers. We also found differences between plastic items composed of the same polymer but from different countries, and between some recycled and nonrecycled plastics. Furthermore, increasing δ13C values were observed after exposure to UV light. The results of the three techniques, and their advantages and limitations, are discussed.

Description: Single particle inductively coupled plasma mass spectrometry (SP-ICP-MS) has become a well-established technique for the detection, size characterization and quantification of inorganic nanoparticles but its use for the analysis of micro- and nanoparticles composed of carbon has been scarce. Here, the analysis of a microplastic suspensions by ICP-MS operated in single particle mode using microsecond dwell times is comprehensively discussed. The detection of polystyrene microparticles down to 1.2 μm was achieved by monitoring the 13C isotope. Plastic microparticles of up to 5 μm were completely volatized and their components atomized, which allowed the detection of microplastics, their quantification using aqueous dissolved carbon standards, and the measurement of the size-distribution of the detected particles. Limits of detection of 100 particles per milliliter were achieved for an acquisition time of 5 min. The method developed was applied to the screening of microplastics in personal care products and released from food packagings. The chemical identity of the detected microplastics was confirmed by attenuated total reflectance Fourier-transform infrared spectroscopy.

Description: Favorable interspecies associations prevail in natural microbial assemblages. Some of these favorable associations are co-metabolic dependent partnerships in which extracellular electrons are exchanged between species. For such electron exchange to occur, the cells must exhibit electroactive interfaces and get involved in direct cell-to-cell contact (Direct Interspecies Electron Transfer/DIET) or use available conductive mineral grains from their environment (Conductive-particle-mediated Interspecies Electron Transfer/CIET). This review will highlight recent discoveries and knowledge gaps regarding DIET and CIET interspecies associations in artificial co-cultures and consortia from natural and man-made environments and emphasize approaches to validate DIET and CIET. Additionally, we acknowledge the initiation of a movement towards applying electric syntrophies in biotechnology, bioremediation and geoengineering for natural attenuation of toxic compounds. Next, we have highlighted the urgent research needs that must be met to develop such technologies.

Description: Highlights • A total of 1455 crustal events in Santorini-Amorgos zone have been relocated. • The seismogenic layer along the zone is found to be 12.5 km thick. • Expected moment magnitude of future earthquakes is in the range of 6.3 to 7.2. • High Vp/Vs ratios in northern part of Santorini caldera indicate the presence of melt. • Upward migrating fluids exist at areas with vertical earthquake clusters. The Santorini-Amorgos zone is located in the central part of the Hellenic volcanic arc and is hosting eight large faults as well as Kolumbo and Santorini volcanic centers. The largest earthquake (Mw ~ 7.1) in the southern Aegean during the 20th century also occurred in this area on 9 July 1956. A total of 1868 crustal events were recorded by temporary networks during September 2002 to July 2004 and October 2005 to March 2007, and also by the permanent network from 2011 to 2019. We relocated 1455 of these events by using HypoDD and revealed clusters of earthquakes beneath Kolumbo, Anydros graben, and Santorini-Amorgos ridge. Only the faults in the SW of Anydros, SE of Ios, and along the south coast of Amorgos were delineated by the relocated events. Nearly vertical clusters were observed beneath the island of Anydros, south of Amorgos, and in NE end of Amorgos fault, indicating possible pathways of upward migrating fluids. The seismogenic layer thickness calculated based on the depth distribution of the relocated events was 12.5 km. We combined this thickness with geometrical properties of the faults to calculate the expected moment magnitude of future earthquakes, resulting in a range of 6.3–7.2. In an effort to map the distribution of fluids, the Vp/Vs ratio distribution was estimated by utilizing the event-station travel time data along with crack density, fluid saturation, and Poisson's ratio. The petrophysical parameters observed in the northern part of the Santorini caldera suggest the existence of melt, while those observed in Anydros and in the NE of Amorgos fault support the suggestion of upward migrating fluids in these areas.

Description: The Santorini-Amorgos zone is an area rich in microseismicity at the center of the Hellenic volcanic arc. The microseismicity of the zone is distributed along the Santorini-Amorgos ridge and Kolumbo submarine volcano. In this study, we utilized crustal events that were recorded by temporary networks during September 2002 to July 2004 and October 2005 to March 2007, and also by the permanent network from 2011 to 2020. These events were inverted for their moment tensors by using P-wave polarities as well as SV/P and SH/P amplitude ratios, yielding 74 well-constrained moment tensor solutions. Most of these moment tensors have significant CLVD and isotropic components that are positively correlated to each other (R2 = 0.68). Tensile faulting due to high pore pressure is considered as the most likely cause of the observed non-DC components. The positive and negative non-DC components observed in Kolumbo may be generated by the opening and closing of cracks beneath the shallow (6–7 km) magma chamber due to a steady migration of magmatic fluids from the deep reservoir into the chamber. In Anydros, most of the microearthquakes have positive non-DC components associated with the opening of cracks. It is possible that the extensional deformation and high pore fluid pressure in the area opens subvertical cracks that become pathways for upward migrating fluids. The upward migration of magmatic fluids in an extensional regime such as the Santorini-Amorgos zone can also be viewed as an indication of emerging volcanic activity in this area.

Description: Chemical pollutants, such as pesticides, often leach into aquatic environments and impact non-target organisms. Marine invertebrates have complex life cycles with multiple life-history stages. Exposure to pesticides during one life-history stage potentially influences subsequent stages; a process known as a carry-over effect. Here, we investigated carry-over effects on the jellyfish Aurelia coerulea. We exposed polyps to individual and combined concentrations of atrazine (2.5 μg/L) and chlorpyrifos (0.04 μg/L) for four weeks, after which they were induced to strobilate. The resultant ephyrae were then redistributed and exposed to either the same conditions as their parent-polyps or to filtered seawater to track potential carry-over effects. The percentage of deformities, ephyrae size, pulsation and respiration rates, as well as the metabolic profile of the ephyrae, were measured. We detected a subtle carry-over effect in two metabolites, acetoacetate and glycerophosphocholine, which are precursors of the neurotransmitter acetylcholine, important for energy metabolism and osmoregulation of the ephyrae. Although these carry-over effects were not reflected in the other response variables in the short-term, a persistent reduction of these two metabolites could have negative physiological consequences on A. coerulea jellyfish in the long-term. Our results highlight the importance of considering more than one life-history stage in ecotoxicology, and measuring a range of variables with different sensitivities to detect sub-lethal effects caused by anthropogenic stressors. Furthermore, since we identified few effects when using pesticides concentrations corresponding to Australian water quality guidelines, we suggest that future studies consider concentrations detected in the environment, which are higher than the water quality guidelines, to obtain a more realistic scenario by possible risk from pesticide exposure.

Description: The Kerguelen Islands are part of the French Southern Territories, located at the limit of the Indian and Southern oceans. They are highly impacted by climate change, and coastal marine areas are particularly at risk. Assessing the responses of species and populations to environmental change is challenging in such areas for which ecological modelling can constitute a helpful approach. In the present work, a DEB-IBM model (Dynamic Energy Budget – Individual-Based Model) was generated to simulate and predict population dynamics in an endemic and common benthic species of shallow marine habitats of the Kerguelen Islands, the sea urchin Abatus cordatus. The model relies on a dynamic energy budget model (DEB) developed at the individual level. Upscaled to an individual-based population model (IBM), it then enables to model population dynamics through time as a result of individual physiological responses to environmental variations. The model was successfully built for a reference site to simulate the response of populations to variations in food resources and temperature. Then, it was implemented to model population dynamics at other sites and for the different IPCC climate change scenarios RCP 2.6 and 8.5. Under present-day conditions, models predict a more determinant effect of food resources on population densities, and on juvenile densities in particular, relative to temperature. In contrast, simulations predict a sharp decline in population densities under conditions of IPCC scenarios RCP 2.6 and RCP 8.5 with a determinant effect of water warming leading to the extinction of most vulnerable populations after a 30-year simulation time due to high mortality levels associated with peaks of high temperatures. Such a dynamic model is here applied for the first time to a Southern Ocean benthic and brooding species and offers interesting prospects for Antarctic and sub-Antarctic biodiversity research. It could constitute a useful tool to support conservation studies in these remote regions where access and bio-monitoring represent challenging issues.

Description: Methane generation from seagrass contributes to green-house gases emissions but can also be a potential controlled biogas source. Understanding the natural fluctuations of emissions and the biotic and abiotic factors underlying such variations is essential. In this work, CH4 emission from beach-cast seagrass from the High-Adriatic coast was analysed. Biochemical methane potential (BMP) tests were used to evaluate CH4 generation at different temperatures (30 °C and 35 °C) and salinity levels (from 0‰ to 35‰), consistent with the typical observed environmental conditions. The changes in the microorganism community composition were investigated by means of amplicon metagenomics sequencing. The results underlined a specific CH4 emission in the range of 0.90–1.37 NmL CH4/g Volatile Solids (VS) d at 35 °C and 0.36–0.50 NmL CH4/g VS d at 30 °C. The most intense methane generation was observed at intermediate salinity levels of 18‰ at 35 °C and 9‰ at 30 °C. The total seasonal emission from the investigated beach-cast seagrass was estimated as 0.1399 mmol CH4/m2g. The microbial community analysis highlighted that Rhodobacteraceae was the most abundant family, coherently with its abundance in the marine environment. Low salinity (0–9‰) samples showed a prevalence of carbohydrate–degrading Ruminococcaceae, while the carbohydrate-fermenting Petrotogaceae were more abundant in high salinity (18–35‰) samples. The total lack of an important functional class was not noticed in any salinity level, except for sulphate-reducing bacteria, which were virtually absent when salinity was 0‰. The present study allows a better understanding of the environmental conditions resulting in a higher methanogenic potential and an enhanced comprehension of the bacterial communities associated to this process. The obtained information can be of help for designing efficient systems for producing methane from seagrass wrack, as well as for selecting the most appropriate managing route among the currently available technologies (such as on-site environmental preservation, composting, anaerobic digestion).

Description: Transdisciplinary research is a promising approach to address sustainability challenges arising from global environmental change, as it is characterized by an iterative process that brings together actors from multiple academic fields and diverse sectors of society to engage in mutual learning with the intent to co-produce new knowledge. We present a conceptual model to guide the implementation of environmental transdisciplinary work, which we consider a “science with society” (SWS) approach, providing suggested activities to conduct throughout a seven-step process. We used a survey with 168 respondents involved in environmental transdisciplinary work worldwide to evaluate the relative importance of these activities and the skills and characteristics required to implement them successfully, with attention to how responses differed according to the gender, geographic location, and positionality of the respondents. Flexibility and collaborative spirit were the most frequently valued skills in SWS, though non-researchers tended to prioritize attributes like humility, trust, and patience over flexibility. We also explored the relative significance of barriers to successful SWS, finding insufficient time and unequal power dynamics were the two most significant barriers to successful SWS. Together with case studies of respondents’ most successful SWS projects, we create a toolbox of 20 best practices that can be used to overcome barriers and increase the societal and scientific impacts of SWS projects. Project success was perceived to be significantly higher where there was medium to high policy impact, and projects initiated by practitioners/other stakeholders had a larger proportion of high policy impact compared to projects initiated by researchers only. Communicating project results to academic audiences occurred more frequently than communicating results to practitioners or the public, despite this being ranked less important overall. We discuss how these results point to three recommendations for future SWS: 1) balancing diverse perspectives through careful partnership formation and design; 2) promoting communication, learning, and reflexivity (i.e., questioning assumptions, beliefs, and practices) to overcome conflict and power asymmetries; and 3) increasing policy impact for joint science and society benefits. Our study highlights the benefits of diversity in SWS - both in the types of people and knowledge included as well as the methods used - and the potential benefits of this approach for addressing the increasingly complex challenges arising from global environmental change.

Description: The Quaternary history of the Atlantic Canadian inner shelf shares some similarities with the North Sea and northern United States of America (US) Atlantic coast, with the influence of large-scale glaciation and subsequent sea level transgression being the main drivers of seafloor morphology, sedimentology, and uppermost stratigraphy. The geology of the inner shelf, generally confined to 100 m water depth for this study, is an important constraint on the development of offshore renewables, in particular wind energy. Offshore wind has seen rapid growth, particularly in Europe and Asia, where the industry has now experienced decades of production. In the US, one small-scale production farm and many hundreds of MW are in the production pipeline. In contrast, offshore wind in Canada, despite onshore installed wind capacity that ranks highly globally, lacks any operating turbines and there are no plans for development in the wind resource-rich Atlantic Canadian region. In this study, the geological constraints on offshore wind in Atlantic Canada are explored. Generally, the available offshore wind resource is high, and thus the main geophysical constraint on the development of offshore wind energy converters is the inner shelf geology. Several sites with available high-resolution geophysical data are selected for in-depth analysis and comparison with production and planned offshore wind farm sites found elsewhere. In general, a lack of sufficiently thick Quaternary sedimentation—necessary for the most common bottom-fixed foundations for wind turbines—will make developing offshore wind in Atlantic Canada challenging when compared with North Sea and US Atlantic Coast locations. A few locations may be suitable geologically, such as Sable Island Bank in Nova Scotia (thick package of sands), Northumberland Strait between Prince Edward Island and Nova Scotia (shallow firm seabed and sandbanks), Baie des Chaleurs in New Brunswick/Québec (thick, low relief fine sediments), and St. George's Bay, Newfoundland (shallow, postglacially modified moraine). Highlights • Glaciated shelves in Atlantic Canada present distinct challenges for offshore wind foundations. • Few analogies exist between Atlantic Canadian shelf sites and offshore wind sites elsewhere. • Piles—typical offshore wind foundations—require thick sediments, rare in Atlantic Canada. • Thin sand/cobble blankets over bedrock are ubiquitous but thick sand banks/mud basins exist. • The inner shelf seabed geology is variable and historically data collection has focused elsewhere.

Description: The occurrence of neurotoxicity caused by xenobiotics such as pesticides (dichlorodiphenyltrichloroethane, organophosphates, pyrethroids, etc.) or metals (mercury, lead, aluminum, arsenic, etc.) is a growing concern around the world, particularly in vulnerable populations with difficulties on both detection and symptoms treatment, due to low economic status, remote access, poor infrastructure, and low educational level, among others features. Despite the numerous molecular markers and questionnaires/clinical evaluations, studying neurotoxicity and its effects on cognition in these populations faces problems with samples collection and processing, and information accuracy. Assessing cognitive changes caused by neurotoxicity, especially those that are subtle in the initial stages, is fundamentally challenging. Finding accurate, non-invasive, and low-cost strategies to detect the first signals of brain injury has the potential to support an accelerated development of the research with these populations. Saliva emerges as an ideal pool of biomarkers (with interleukins and neural damage-related proteins, among others) and potential alternative diagnostic fluid to molecularly investigate neurotoxicity. As a source of numerous neurological biomarkers, saliva has several advantages compared to blood, such as easier storage, requires less manipulation, and the procedure is cheaper, safer and well accepted by patients compared with drawing blood. Regarding cognitive dysfunction, neuropsychological batteries represent, with their friendly interface, a feasible and accurate method to evaluate the eventual cognitive deficits associated with neurotoxicity in people from diverse cultural and educational backgrounds. The association of these two tools, saliva and neuropsychological batteries, to cover the molecular and cognitive aspects of neurotoxicity in vulnerable populations, could potentially increase the prevalence of early intervention and successful treatment.

Description: The reaction surface area of hydrate (RSAH) inherently controls the reaction rate of hydrate dissociation in the pore spaces, which further affects the gas production behaviour of the hydrate-bearing sediments. The objective of this work is to measure and describe the RSAH evolution during MH dissociation and analyse its implications for gas production. The CT images obtained from different dissociation stages showed the RSAH decreased slowly in the early stage of dissociation and rapidly in the later stage. By considering the pore structure features of sediment, a fractal method was proposed to predict the relationship between RSAH and hydrate saturation, which showed better agreement with the CT experimental results than that of Yousif's model. Further hydrate production numerical simulations embedded with different RSAH predictions indicated that the hydrate production process was significantly influenced by the variations in RSAH. The simulated gas production rate based on the fractal model was lower than that of Yousif's model, the far-field pressure drop in the fractal model was slower, and the advance of the dissociation front and the transfer of the pressure field in Yousif's model was faster than that of the fractal model. Highlights • The changes in hydrate reaction surface area during hydrate dissociation are experimentally measured and analysed. • A fractal model considering the pore structure characteristics of porous media is proposed and experimentally validated. • A comparison of the hydrate dissociation rate predicted by the proposed fractal model and by Yousif’s model is made. • Implications of reaction surface evolution during the hydrate dissociation for hydrate productions are modeled.

Description: Adaptive sampling and situational awareness for autonomous underwater vehicles (AUVs) is a major improvement in ocean research. By only sampling the feature of interest in a feature-relevant domain instead of a covering a whole area expensive ship time can be saved and at the same time a more comprehensive data set can be obtained. A classical marine example where adaptive sampling is useful is sampling of boundary layers such as the thermocline because the boundary layer thickness is very small compared to the depth of the water column. These boundary layers play an important role in many ocean related disciplines such as marine biology, physical oceanography and underwater acoustics. In this paper an unscented Kalman filter (UKF) based extremum seeking control (ESC) approach is presented to detect and track such boundary layers. Simulation results for different use cases are presented to show its effectiveness.

Description: The Q10 temperature coefficient, which is widely used in scientific literature, is a measure of the temperature sensitivity of chemical reaction rates or biological processes. However, the conclusions drawn from applying this coefficient to experimental data obtained from biological processes are not universal. In many biological processes, Q10 values are often discordant with the results predicted by the Arrhenius law. The hypothesis tested in the present study is that this problem arises mainly from the fact that the Q10 coefficient is defined by the ratio between rates described by exponential laws instead of power laws. Considering this hypothesis and the need to review the mathematical laws and models currently used to describe rates and Q10 coefficients, we propose a model beyond the usual Arrhenius theory or exponential decay law herein. The proposed mathematical model is based on the theory of deformed exponential functions, with the ordinary Q10 model representing the conventional exponential function. Therefore, all results following the standard model remain valid. Moreover, we include a Q10 free open-source code, written in Python, and compatible with Windows, Linux and macOS platforms. The validation of the proposed model and confirmation of the given hypothesis were performed based on the following temperature-dependent biological processes: soil organic carbon (SOC) decomposition (which is essential to forecast the impact of climate change on terrestrial ecosystems); the metabolism of Arctic zooplankton; physiological processes of the respiratory and cardiovascular systems; rate of oxygen consumption in mitochondria of the eurythermal killifish Fundulus heteroclitus, and leaf respiration.

Description: Since 2010, the Soil Moisture and Ocean Salinity (SMOS) satellite mission monitors the earth emission at L-Band. It provides the longest time series of Sea Surface Salinity (SSS) from space over the global ocean. However, the SSS retrieval at high latitudes is a challenge because of the low sensitivity L-Band radiometric measurements to SSS in cold waters and to the contamination of SMOS measurements by the vicinity of continents, of sea ice and of Radio Frequency Interferences. In this paper, we assess the quality of weekly SSS fields derived from swath-ordered instantaneous SMOS SSS (so called Level 2) distributed by the European Space Agency. These products are filtered according to new criteria. We use the pseudo-dielectric constant retrieved from SMOS brightness temperatures to filter SSS pixels polluted by sea ice. We identify that the dielectric constant model and the sea surface temperature auxiliary parameter used as prior information in the SMOS SSS retrieval induce significant systematic errors at low temperatures. We propose a novel empirical correction to mitigate those sources of errors at high latitudes. Comparisons with in-situ measurements ranging from 1 to 11 m depths spotlight huge vertical stratification in fresh regions. This emphasizes the need to consider in-situ salinity as close as possible to the sea surface when validating L-band radiometric SSS which are representative of the first top centimeter. SSS Standard deviation of differences (STDD) between weekly SMOS SSS and in-situ near surface salinity significantly decrease after applying the SSS correction, from 1.46 pss to 1.28 pss. The correlation between new SMOS SSS and in-situ near surface salinity reaches 0.94. SMOS estimates better capture SSS variability in the Arctic Ocean in comparison to TOPAZ reanalysis (STDD between TOPAZ and in-situ SSS = 1.86 pss), particularly in river plumes with very large SSS spatial gradients.

Description: The exhumation of peridotite rocks in oceanic transform zones passes by the rheological transition between the ductile and brittle deformation until the complete emplacement in the oceanic lithosphere. The São Pedro and São Paulo Archipelago (SPSPA), in the Equatorial Atlantic, records the deformational products of ductile, brittle and the rocks/fluid interaction generating specific structures in each domain. The deformational stages are related to the transpressional and transtensional geodynamics of São Paulo Transform Fault. Firstly, during transpression, exhumation occurs associated with the ductile domain causing intense mylonitization in temperatures between ~700° and 800 °C, defined by olivine and orthopyroxene recrystallization. The interaction with fluids initially originated from the mantle generates amphibole and oxide-rich layers marking the passage to a semi-brittle deformation. The continuation of peridotite exhumation, associated with an NW-SE shortening and transpressional led to a higher availability of hydrothermal fluids. As a consequence, four serpentinization episodes are recorded, which are associated with semi-brittle to brittle transition under temperatures between 300° and 400 °C. Finally, the complete exhumation and establishment of brittle mechanisms led to carbonatation phase near the surface, with temperatures ranging from 300° to 150 °C. The active NW-SE tectonic stress generated E-W strike-slip faults that were filled by carbonates recording the final exhumation stage.

Description: The present state of constantly increasing plastic pollution is the major concern of scientific researchers. The conventional techniques applied (i.e., burning and landfilling) to get plastic degraded from the environment are inadequate due to harmful byproducts and limited to its recycling. In this review, we have recapitulated recent biotechnological approaches, including synthetic microbial consortia, systems biology tools, and genetic engineering techniques which can pave the path towards the plastic bioremediation and degradation. Moreover, potential plastic degrader microbes and their degradation pathways are also summarized. Lastly, this review focuses on enhancing the understanding of the degradation ability of microorganisms using contemporary biotechnological tools.

Description: Atmospheric deposition of aerosols to the ocean provides an important pathway for the supply of vital micronutrients, including trace metals. These trace metals are essential for phytoplankton growth, and therefore their delivery to marine ecosystems can strongly influence the ocean carbon cycle. The solubility of trace metals in aerosols is a key parameter to better constrain their potential impact on phytoplankton growth. To date, a wide range of experimental approaches and nomenclature have been used to define aerosol trace metal solubility, making data comparison between studies difficult. Here we investigate and discuss several laboratory leaching protocols to determine the solubility of key trace metals in aerosol samples, namely iron, cobalt, manganese, copper, lead, vanadium, titanium and aluminium. Commonly used techniques and tools are also considered such as enrichment factor calculations and air mass back-trajectory projections and recommendations are given for aerosol field sampling, laboratory processing (including leaching and digestion) and analytical measurements. Finally, a simple 3-step leaching protocol combining commonly used protocols is proposed to operationally define trace metal solubility in aerosols. The need for standard guidelines and protocols to study the biogeochemical impact of atmospheric trace metal deposition to the ocean has been increasingly emphasised by both the atmospheric and oceanographic communities. This lack of standardisation currently limits our understanding and ability to predict ocean and climate interactions under changing environmental conditions.

Description: Highlights • Regional brain iron concentrations are heterogenous. • Regional distribution of iron is most consistent with ferritin mRNA expression. • SEC-ICP-MS reveals the protein masses that cytosolic iron is associated with. • More than 50 % of cytosolic iron is associated with ferritin. Iron is essential for brain development and health where its redox properties are used for a number of neurological processes. However, iron is also a major driver of oxidative stress if not properly controlled. Brain iron distribution is highly compartmentalised and regulated by a number of proteins and small biomolecules. Here, we examine heterogeneity in regional iron levels in 10 anatomical structures from seven post-mortem human brains with no apparent neuropathology. Putamen contained the highest levels, and most case-to-case variability, of iron compared with the other regions examined. Partitioning of iron between cytosolic and membrane-bound iron was generally consistent in each region, with a slightly higher proportion (55 %) in the ‘insoluble’ phase. We expand on this using the Allen Human Brain Atlas to examine patterns between iron levels and transcriptomic expression of iron regulatory proteins and using quantitative size exclusion chromatography-inductively coupled plasma-mass spectrometry to assess regional differences in the molecular masses to which cytosolic iron predominantly binds. Approximately 60 % was associated with ferritin, equating to approximately 25 % of total tissue iron essentially in storage. This study is the first of its kind in human brain tissue, providing a valuable resource and new insight for iron biologists and neuroscientists, alike.

Description: The aim of this study was to investigate the syntrophic methanogenesis from the perspective of energy transfer and competition. Effects of redox materials and redox potential on direct interspecies electron transfer (DIET) were examined through thermodynamic analysis based on the energy distribution principle. Types of redox materials could affect the efficiency of DIET via changing the total energy supply of the syntrophic methanogenesis. Decreasing system redox potential could facilitate DIET through increasing the total available energy. The competition between hydrogenotrophic methanogens and DIET methanogens might be the reason for the low proportion of the DIET pathway in the syntrophic methanogenesis. A facilitation mechanism of DIET was proposed based on the energy distribution. Providing sufficient electrons, inhibiting hydrogenotrophic methanogens and adding more competitive redox couples to avoid hydrogen generation might be beneficial for the facilitation of DIET.

Description: Highlights • NH4NO3, Tris-HCl, and NH4CH3COO are optimal buffers for use in SEC-ICP-MS metalloprotein analyses. • Optimal range of buffer concentration is 50–200 mM in SEC-ICP-MS. • 100 mM concentration reduces both protein column interactions and ICP-MS maintenance. • Dextran-based columns are best suited for the analysis of apo-copper proteins. The correct identification of the metalloproteins present in human tissues and fluids is essential to our understanding of the cellular mechanisms underpinning a host of health disorders. Separation and analysis of biological samples are typically done via size exclusion chromatography hyphenated with inductively coupled plasma-mass spectrometry (SEC-ICP-MS). Although this technique can be extremely effective in identification of potential metalloproteins, the choice of mobile phase may have a marked effect on results, results by adversely affecting metal-protein bonds of the metalloproteins of interest. To assess the choice of mobile phase on SEC-ICP-MS resolution and the resulting metalloproteome pattern, we analysed several different sample types (brain homogenate; Cu/Zn-superoxide dismutase (SOD1); a molecular weight standard mix containing ferritin (Ft), ceruloplasmin (Cp), cytochrome c (CytC), vitamin B12 (B12) and thyroglobulin (Tg) using six different mobile phase conditions (200 mM, pH 7.5 solutions of ammonium salts nitrate, acetate, and sulfate; HEPES, MOPS and Tris-HCl). Our findings suggest that ammonium nitrate, ammonium acetate and Tris-HCl are optimal choices for the mobile phase, with the specific choice being dependent on both the number of samples and method of detection that is hyphenated with separation. Furthermore, we found that MOPS, HEPES and ammonium sulfate mobile phases all caused significant changes to peak resolution, retention time and overall profile shape. MOPS and HEPES, in particular, produced additional Fe peaks that were not detected with any of the other mobile phases that were investigated. As well as this, MOPS and HEPES both caused significant concentration dependent matrix suppression of the internal standard.

Description: Symbiotic relationships range from parasitic to mutualistic, yet all endosymbionts face similar challenges, including evasion of host immunity. Many symbiotic organisms have evolved similar mechanisms to face these challenges, including manipulation of the host's transforming growth factor-beta (TGFβ) pathway. Here we investigate the TGFβ pathway in scelaractinian corals which are dependent on symbioses with dinoflagellates from the family Symbiodiniaceae. Using the Caribbean coral, Orbicella faveolata, we explore the effects of enhancement and inhibition of the TGFβ pathway on host gene expression. Following transcriptomic analyses, we demonstrated limited effects of pathway manipulation in absence of immune stimulation. However, manipulation of the TGFβ pathway significantly affects the subsequent ability of host corals to mount an immune response. Enhancement of the TGFβ pathway eliminates transcriptomic signatures of host coral immune response, while inhibition of the pathway maintains the response. This is, to our knowledge, the first evidence of an immunomodulatory role for TGFβ in a scelaractinian coral. These findings suggest variation in TGFβ signaling may have implications in the face of increasing disease prevelance. Our results suggest that the TGFβ pathway can modulate tradeoffs between symbiosis and immunity. Further study of links between symbiosis, TGFβ, and immunity is needed to better understand the ecological implications of these findings.

Description: Highlights • Microplastics act as anthropogenic vectors of trace metals in freshwaters. • Adsorption capacity of microplastics is enhanced by biofilms but is not strong as natural substrates. • Biofilms alter the adsorption kinetics and mechanisms of trace metals onto microplastics. • Microplastics enhance exchange rates of trace metals between water and solid materials. • Anthropogenic substrate is necessary in evaluation of migration and fate of trace metals. Microplastics (MPs) are ubiquitous in freshwater environments, and represent an emerging anthropogenic vector for contaminants, such as trace metals. In this study, virgin expanded polystyrene (PS) particles were placed in a eutrophic urban lake and a reservoir serving as the resource of domestic water for 4 weeks, to develop biofilms on the surface. For comparison, natural adsorbents in the form of suspended particles and surficial sediment were also sampled from these waterbodies. The trace metal adsorption properties of anthropogenic (virgin and biofilm covered microplastics) and natural substrates were investigated and compared via batch adsorption experiments. The adsorption isotherms fitted the Langmuir model, revealed that biofilms could enhance the trace metal adsorption capacity of MPs. However, natural substrates still had a greater adsorption capacity. Biofilms also alter the adsorption kinetics of trace metals onto MPs. The process of adsorption onto virgin MPs was dominated by intraparticle diffusion, whereas film diffusion governed adsorption onto biofilm covered microplastics and natural substrates. The trace metal adsorption of all the substrates was significantly dependent on pH and ionic strength. The adsorption mechanisms were further analyzed by SEM-EDS and FT-IR. The enhancement of adsorption was mainly attributed to complexation with functional groups contained in the biofilms, including carboxyl, amino, and phenyl-OH. Collectively, biofilm development intensifies the role of MPs in the migration and fate of trace metals in freshwater, since it does not give MPs an edge over natural substrates in adsorption.

Description: Highlights • New insights of CH4 and CO2 hydrates are explored using MD strategy. • The bubble evolution appears to be important over dissociation process. • RDF, MSD, AOP, and diffusion coefficient can be used to examine hydrate stability. • The most stable structure of CH4 and CO2 molecules in the gas hydrate is found. • A promising match is noticed between the MD and literature findings. A comprehensive knowledge and precise estimation of the dynamic, structural, and thermodynamic characteristics of hydrates are needed to assess the stability of gas hydrates. Thermodynamic model and experimental studies can be utilized to compute the physical and dynamic properties of hydrate structures. The use of molecular dynamic (MD) simulation is a well-established approach in gas hydrate studies at the atomic level where the properties of interest are obtained from the numerical solution of Newtonian equations. The present work uses MD simulations by employing the constant temperature-constant pressure (NPT), constant temperature-constant volume (NVT) conditions, and the consistent valence force field (CVFF) to monitor the stability and decomposition of methane and carbon dioxide gas hydrates with different compositions. The effects of temperature and composition on the hydrate stability are investigated. In this study, we also compute the radial distribution function, mean square displacement, diffusion coefficient, lattice parameter, potential energy, dissociation enthalpy as well as the density of methane and carbon dioxide under various thermodynamic and process conditions. The formation of methane and carbon dioxide bubbles is studied to investigate bubble evolution during hydrate dissociation. The sizes of methane and carbon dioxide bubbles are not the same due to different solubility conditions of methane and carbon dioxide in liquid water. In addition, the influences of pressure and temperature on the lattice parameter and density of clathrate hydrates are discussed. The obtained results are consistent with previous theoretical and experimental findings, implying that the methodology followed in this work is reliable. The most stable arrangement of methane and carbon dioxide molecules in the gas hydrate is found. The insights/findings of this study might be useful to further understand detailed transport phenomena (e.g., molecular interactions, gas production rate, carbon dioxide replacement, and carbon dioxide capture) involved in the process of carbon dioxide injection into gas hydrate reservoirs.

Description: Deep-ocean islands have long been associated with the generation of oceanic eddies in their wakes. However, their interaction with incoming eddies has seldom been considered. This study focuses on the characterization of background and locally generated mesoscale eddies in the Cabo Verde archipelago between 2003 and 2014. Special attention is given to the interaction of incoming eddies with the bathymetry of the islands, along with their impacts on the local generation of eddies. Island-induced wind-shear effects are also considered. In addition, some examples of the biological response to background and locally generated eddies are discussed. This is achieved by combining remote-sensing satellite observations for wind, sea surface height, and chlorophyll-a (Chla) surface concentrations. The results show that the interaction between incoming background eddies and the archipelago is a recurrent phenomenon, which results in eddy deflection, splitting, merging, intensification, and termination (sorted by highest to lowest number of occurrences). Local island-induced disturbances are also significant, mainly due to atmospheric effects. Such processes result in the generation of island-induced eddies and in wind-mediated eddy intensification and confinement, more often observed in the leeward group. Nonetheless, it is strongly suggested that many of the locally generated eddies are a direct product or by-product of the interaction of background eddies with the islands. With respect to the biological realm, a locally generated cyclonic eddy is observed to originate a pronounced phytoplankton bloom in the vicinity of the tallest island. Nonetheless, background eddies generated off the African coast are often associated with enhanced Chla concentrations when they intersect the archipelago. Such observations challenge the idea that local biological productivity in deep oceanic islands is exclusively driven by island-induced mechanisms.

Description: In an era of electronics, recovering the precious metal such as gold from ever increasing piles of electronic-wastes and metal-ion infested soil has become one of the prime concerns for researchers worldwide. Biological mining is an attractive, economical and non-hazardous to recover gold from the low-grade auriferous ore containing waste or soil. This review represents the recent major biological gold retrieval methods used to bio-mine gold. The biomining methods discussed in this review include, bioleaching, bio-oxidation, bio-precipitation, bio-flotation, bio-flocculation, bio-sorption, bio-reduction, bio-electrometallurgical technologies and bioaccumulation. The mechanism of gold biorecovery by microbes is explained in detail to explore its intracellular mechanistic, which help it withstand high concentrations of gold without causing any fatal consequences. Major challenges and future opportunities associated with each method and how they will dictate the fate of gold bio-metallurgy from metal wastes or metal infested soil bioremediation in the coming future are also discussed. With the help of concurrent advancements in high-throughput technologies, the gold bio-exploratory methods will speed up our ways to ensure maximum gold retrieval out of such low-grade ores containing sources, while keeping the gold mining clean and more sustainable.

Description: One of the best-known greenhouse gases, CO2, has been increasing in the last decade of about 1.7%. To overcome the well-known global problems related to this gas, researchers of all over the world are working very hard in order to develop any strategies to seriously solve this issue. In this chapter, the authors focus their attention on one of the possible solutions to the problem: bacteria that are CO2 capture cells which have carried out this task since ancient times. In our work we make an excursus on all the biochemical processes of CO2 capture carried out by bacteria, ending with a detailed comparison of the most studied enzymes. One of the alternatives will be to genetically modify the organisms known to date to speed up their conversion process.

Description: The book presents multivariate statistical methods useful in geological analysis. The essential distinction between multivariate analysis as applied to full-space data (measurements on lengths, heights, breadths etc.) and compositional data is emphasized with particular reference to geochemical data. Each of the methods is accompanied by a practically oriented computer program and backed up by appropriate examples. The computer programs are provided on a compact disk together with trial data-sets and examples of the output. An important feature of this book is the graphical system developed by Dr. Savazzi which is entitled Graph Server.

Description: The sea-ice export out of the central Arctic through the Fram Strait is a key variable in the Arctic climate system. Satellite data provide the only basis for mapping ice features with a high spatial and temporal resolution in polar regions. An automatic drift algorithm has been employed and optimized to monitor the sea-ice drift velocity in the Greenland Sea with AVHRR data. The combination of the ice drift and the spatial ice distribution provides an insight into the ice transport processes along the coast of Greenland. The combination with sea-ice thickness measurements allows an estimation of the spatial distribution of the sea-ice mass flux. The seasonal and spatial variability of the mass flux allows further predictions of the meridional melting and freezing processes along the East Greenland Current. This investigation covers the years 1993 and 1994. Seasonal and spatial distributions of the sea-ice drift were derived. The derived absolute values in this study are in good agreement with estimates proposed by other authors.

Description: High-resolution Nd- and Pb-isotope time series for the last 8 Myr are reported for four Atlantic ferromanganese crusts, dated by 10Be/9Be chronology. These are compared to new high-resolution and high-precision Pb-isotope time series and recently published Nd-isotope time series for two previously studied crusts from the NW Atlantic Ocean. These records allow a more detailed examination of Atlantic deepwater variability over the time period of intensification of Northern Hemisphere Glaciation (NHG). Changes in the Pb-isotope time series started after 3 Ma, but were most dramatic over the last 1.8 Myr, coinciding with changes of Pb-isotopes in the Arctic Ocean. This latter change post-dates the intensification of NHG at 3.1 to 2.5 Ma and reflects an increase in the input of material eroded from the Archean Shield of Canada and Greenland. Shifts in Nd- and Pb-isotope compositions in a crust from the Blake Plateau occur before ∼5 Ma and most prominent at ∼8 Ma suggest that water masses from either the Pacific or Southern Ocean influenced the isotope composition of this crust. The relatively high εNd values around 8 Ma recorded by the Blake Plateau crust are explained by a contribution of eastward flowing Pacific water through the Panama Gateway into the Caribbean Sea. This high εNd signal decreased between 8 and 5 Ma suggesting that the supply of Pacific water into the Caribbean became restricted. This is earlier than the Caribbean seawater salinity increase at 4.2 Ma deduced from δ18O data, and may indicate that there was only a surface water connection between the Caribbean and Pacific between ∼5 and 4.2 Ma. The closure of the Panama Gateway to intermediate and deep water exchange (〉200 m depth) apparently occurred much earlier than the intensification of Northern Hemisphere Glaciation at 3.1–2.5 Ma, and cannot therefore have been a direct cause of this climatic change, but may, as recently argued, only have been a necessary precondition

Description: Mixed methane–sulfide hydrates and carbonates are exposed as a pavement at the seafloor along the crest of one of the accretionary ridges of the Cascadia convergent margin. Vent fields from which methane-charged, low-salinity fluids containing sulfide, ammonia, 4He, and isotopically light CO2 escape are associated with these exposures. They characterize a newly recognized mechanism of dewatering at convergent margins, where freshening of pore waters from hydrate destabilization at depth and free gas drives fluids upward. This process augments the convergence-generated overpressure and leads to local dewatering rates that are much higher than at other margins in the absence of hydrate. Discharge of fluids stimulates benthic oxygen consumption which is orders of magnitude higher than is normally found at comparable ocean depths. The enhanced turnover results from the oxidation of methane, hydrogen sulfide, and ammonia by vent biota. The injection of hydrate methane from the ridge generates a plume hundreds of meters high and several kilometers wide. A large fraction of the methane is oxidized within the water column and generates δ13C anomalies of the dissolved inorganic carbon pool.

Description: Controversy surrounding the mechanisms and controls on argon diffusion in K-feldspar has led us to undertake direct diffusion measurements on a crystal with simple microtextures, over a range of temperatures. Measurements of argon diffusion profiles in a gem-quality iron-rich orthoclase heated in a cold seal apparatus, have been undertaken in situ using an ultra-violet laser ablation microprobe (UVLAMP) technique. The results agree very closely with the previously determined bulk values for Benson Mines orthoclase (activation energy ( E)=43.8±1 kcal mol -1) and vacuum furnace cycle-heating studies of K-feldspars ( E=46±6 kcal mol -1). However, instead of defining a single activation energy ( E) and diffusion coefficient ( Do), the data yield two sets of parameters: a low-temperature (550-720°C) array with an E of 47.2±2.5 kcal mol -1 (198.2±10.5 kJ mol -1) and a Do of 0.0374 +0.1123-0.0281 cm 2 s -1, and a high-temperature (725-1019°C) array with an E of 63.8±3.4 kcal mol -1 (268.0±14.3 kJ mol -1) and a Do of 55.0 +225.5-44.2 cm 2 s -1. The new results closely reproduce two sets of apparent activation energies previously measured in cycle-heating studies of Madagascar K-feldspar (40±3 and 57±3 kcal mol -1). Previous interpretations of the two arrays have included multiple domains with variable activation energies and fast track diffusion. However, the UV depth profile analyses indicate simple diffusion to the grain surface and importantly, diffusion radii calculated by combining the UVLAMP and cycle-heating data, are the same as the physical grain sizes used in the experiments, around 1 mm. Vacuum furnace stepped heating experiments on slowly cooled K-feldspars have been interpreted as showing diffusion radii of around 6 μm and indicate complex populations of sub-grains. This study indicates that Madagascar K-feldspar and thus probably all gem-quality K-feldspars act as single diffusion domains and that short-circuit (or pipe) diffusion was not an important loss mechanism. An apparent diffusion compensation relationship in the stepped heating data for Madagascar K-feldspar implies that similar relationships seen in other K-feldspars are a result of a range of diffusion mechanisms.

Description: Sediment proxy data from the Norwegian, Greenland, and Iceland seas (Nordic seas) are presented to evaluate surface water temperature (SST) differences between Holocene and Eemian times and to deduce from these data the particular mode of surface water circulation. Records from planktic foraminiferal assemblages, CaCO3 content, oxygen isotopes of foraminifera, and iceberg-rafted debris form the main basis of interpretation. All results indicate for the Eemian comparatively cooler northern Nordic seas than for the Holocene due to a reduction in the northwardly flow of Atlantic surface water towards Fram Strait and the Arctic Ocean. Therefore, the cold polar water flow from the Arctic Ocean was less influencial in the southwestern Nordic seas during this time. As can be further deduced from the Eemian data, slightly higher Eemian SSTs are interpreted for the western Iceland Sea compared to the Norwegian Sea (ca. south of 70°N). This Eemian situation is in contrast to the Holocene when the main mass of warmest Atlantic surface water flows along the Norwegian continental margin northwards and into the Arctic Ocean. Thus, a moderate northwardly decrease in SST is observed in the eastern Nordic seas for this time, causing a meridional transfer in ocean heat. Due to this distribution in SSTs the Holocene is dominated by a meridional circulation pattern. The interpretation of the Eemian data imply a dominantly zonal surface water circulation with a steep meridional gradient in SSTs.

Description: The widespread view that scleractinian corals in cold and deep waters of high latitudes are slow growing organisms that do not form reefs is challenged by the discovery of a huge coral reef over 13 km in length, 10 to 35 m in height and up to 300 m in width formed by the coral Lophelia pertusa in water depths of 270 to 310 m at 64°N on the Sula Ridge, Mid-Norwegian Shelf. Cruises in 1994, 1995 and manned submersible operations in May 1997 provide data and observations from which the structure and development of the Sula Ridge coral reef have been determined. The Fennoscandian icesheet retreated from the Mid-Norwegian shelf prior to 12,000 years before present and modern oceanographic conditions were established at 8000 years before present. Coral growth since that time has resulted in a large deep-water shelf reef for which recent stable isotopic studies have demonstrated high growth rates for these azooxanthellate cold-water corals. Information on the geometry of deep-water coral reefs and their environmental controls is still fragmentary, controversial and raises issues of conservation in this area of active fishing and oil exploration. This paper reports on the discovery of what is probably one of the largest deep-water coral reefs existing in the northeast Atlantic and indicates that its siting is due to post-glacial structures (iceberg plough marks), events (the second Storegga Slide) and local conditions on the seafloor. Surprisingly, reef accumulation rates on the Sula Ridge are comparable with those measured on tropical coral reefs.

Description: The global sediment mass-age distribution indicates large variations in the rates of carbonate sedimentation through time. The largest mass of carbonate deposited during the entire history of the earth was produced during the Cambrian, possibly following on an episode of phosphogenesis in the Late Precambrian. A second major episode occurred during the Late Devonian, probably reflecting the invasion of land by plants that altered the rock-weathering and soil-forming regimes. Other lesser pulses of carbonate deposition occurred in the Late Permian, Triassic, and Cretaceous. A shift in the locus of carbonate deposition from shallow waters to the deep sea occurred during the Cretaceous.

Description: The possibilities of defining and computing an approximately neutral density variable are reexamined in this paper. There are three desirable properties that a neutral density variable should possess. Firstly, the isosurfaces of this variable should coincide with (approximately) neutral surfaces. This would facilitate the analysis of hydrographic data on the most appropriate mixing and spreading surfaces. Secondly, the horizontal gradients of the neutral density should agree with the gradients of the in situ density, and thirdly the vertical gradient of the neutral density variable should be proportional to the static stability of the water column. A density variable that approximates the latter two properties can be used in ocean circulation models based on layer coordinates, and would reduce substantial errors in present isopycnal models due to the use of a potential density variable. No variable can possess all the three properties simultaneously. The variable γn introduced by Jackett and McDougall (1997, J. Phys. Oceanogr. 27, 237–263) satisfies the first of the properties exactly but is not designed for the use in models. Based on climatological data in the North Atlantic, an alternative neutral density variable ν̃(S, Θ) is defined, which is shown to approximate the two gradient criteria much better than any potential density. We suggest that this neutral density variable may be useful in isopycnal ocean models as an alternative to potential density, since it could significantly reduce errors in thermal wind relation and vertical stability

Description: To investigate patch selectivity in aspidochirotide holothurians, individuals of five species (Holothuria (Halodeima) atra Jäger, H. (H.) edulis Lesson, H. (Microthele) nobilis Selenka, Stichopus chloronotus Brandt and S. variegatus Semper) were subjected to multiple choice experiments. As a food source, sediments were pre-cultivated in petri dishes under different light and nutrient regimes. This resulted in four sediment treatments with different levels of microalgal biomass (measured as chlorophyll a and phaeophytin concentrations). Only two sediment treatments were used for experiments with H. nobilis and S. variegatus. The sediments were offered simultaneously to individual holothurians (six per experiment), and the weights of the sediment in each petri dish at the start and after 48 h were used to calculate a selection index together with confidence intervals for each food type. In experiments with H. atra and H. edulis, the animals exhibited no preference for any food type. In contrast, S. chloronotus significantly selected sediments with the highest contents of microalgae and avoided the sediment with the lowest pigment concentrations. These results were supported by field collections of sediments found directly underneath holothurians. Sediment underneath H. edulis did not differ from the average sediment of the habitat, while H. atra was found on sediments only slightly higher in chlorophyll a. Chlorophyll a concentrations underneath S. chloronotus were distinctly higher than in the adjacent sediment and that underneath H. atra. H. nobilis showed only a weak preference for sediments with higher pigment concentrations in aquarium experiments, and no patch selectivity in this species was found in the field. Stichopus variegatus exhibited a very distinct patch selectivity towards sediments with more nutritional value in both aquaria experiments and field measurements. Thus members of the genus Holothuria had no, or only a weak, tendency to select their food source, whereas both Stichopus species appeared to carefully select the sediment patch to feed on.

Description: In an extended deep-sea study the response of the benthic community to seasonally varying sedimentation rates of organic matter were investigated at a fixed abyssal site in the NE Atlantic (BIOTRANS station or JGOFS station L2 at 47°N–20°W, water depth 〉4500 m) on four legs of METEOR expedition 21 between March and August 1992. The vertical flux at 3500 m depth and temporal variations in the chloroplastic pigment concentration, a measure of phytodetritus deposition, and of total adenylates and total phospholipids, measures of benthic biomass, and of activity of hydrolytic enzymes were observed. The flux patterns in moored sediment traps of total chlorophyll, POC and total flux showed an early sedimentation peak in March/April 1992, followed by low fluxes in May and intermediate ones from June to August. Thus 1992 differed from other years, in which one large flux peak after the spring phytoplankton bloom was observed. Unusually high concentrations of chloroplastic pigments were consistently observed in March 1992, reflecting the early sedimentation input. At the same time biomass of small benthic organisms (bacteria to meiobenthos) and activity of hydrolytic enzymes were higher compared to values from March 1985 and from the following months in 1992. In May and August 1992 pigment concentrations and biomass and activity parameters in the sediment were lower than during previously observed depositions of phytodetrital matter in summer. The data imply that the deep ocean benthic community reacts to small sedimentation events with transient increases in metabolic activity and only small biomass production. The coupling between pelagic and benthic processes is so close that interannual variability in surface water production is “mirrored” by deep-sea benthic processes.

Description: This is the first detailed investigation of the distribution and ecology of living (stained) shallow water (0–6 m) foraminifera along the Skagerrak–Kattegat coast, eastern North Sea. A total of 25 species (13 agglutinated; 12 calcareous) are common in the 169 sediment surface samples which were collected from 27 geographic areas. The sediment grain size and total organic carbon (TOC) content are strongly variable and the salinity and temperature ranges were 10–31‰ and 9–30°C, respectively, at the time of sampling (July to October) but temperatures down to freezing occur during the winter. The species are divided into six environmental categories of which the first five comprise euryhaline and the sixth essentially stenohaline taxa: (1) species associated only with marsh plants, (2) species basically, but not entirely, associated with marsh plants, (3) species basically, but not entirely, restricted to non-marsh areas, (4) species solely recorded in non-marsh intertidal to subtidal environments, (5) species restricted to subtidal areas, (6) species basically living in the most open marine areas. In this region, marshes have a patchy distribution and they are small and compressed due to low tidal ranges (〈40 cm). Balticammina pseudomacrescens (not reported here before) lives in the most elevated, landward, terrestrial parts of marshes and thus defines the uppermost limit of the influence of marine water. However, the marshes are generally dominated by Jadammina macrescens and Miliammina fusca at the landward and seaward sides, respectively. Jadammina macrescens is observed living epiphytically on decaying Carex leaf debris. The most widely distributed euryhaline species are Elphidium williamsoni, Miliammina fusca, Ammonia beccarii, and Haynesina germanica. The former two are common only in sediments with a mud content less than about 60%, whereas the latter two are common even in sediments with 〉80% mud. Ammoscalaria runiana is common only in coarse-grained sediments (〈20% mud) with low TOC (≤0.7%). There are no marked biogeographic boundaries within the Skagerrak–Kattegat area but 10 of the 25 commonly occurring species have not been reported from the adjacent Baltic Sea, probably partly due to the brackish character of the water there. The southern limits of distribution of the northern species, Elphidium albiumbilicatum, Ammotium cassis, and Ophthalmina kilianensis, are in the Kattegat–Baltic Sea.

Description: Although much of the deep sea is physically tranquil, some regions experience near-bottom flows that rework the surficial sediment. During periods of physical reworking, animals in the reworked layer risk being suspended, which can have both positive and negative effects. Reworking can also change the sediment in ecologically important ways, so the fauna of reworked sites should differ from that of quiescent locations. We combined data from two reworked, bathyal sites on the summit of Fieberling Guyot (32°27.631′N, 127°49.489′W; 32°27.581′N, 127°47.839′W) and compared the results with those of more tranquil sites. We tested for differences in the following parameters, which seemed likely to be sensitive to the direct or indirect effects of reworking: (1) the vertical distribution of the meiofauna in the sea bed, (2) the relative abundance of surface-living harpacticoids, (3) the proportion of the fauna consisting of interstitial harpacticoids, (4) the ratio of harpacticoids to nematodes. We found that the vertical distributions of harpacticoid copepods, ostracods, and kinorhynchs were deeper on Fieberling. In addition, the relative abundance of surface-living harpacticoids was less, the proportion of interstitial harpacticoids was greater, and the ratio of harpacticoids to nematodes was greater on Fieberling. These differences between Fieberling and the comparison sites suggest that physical reworking affects deep-sea meiofauna and indicate the nature of some of the effects.

Description: The percentage of the structural Fe(II) in clay minerals that is readily oxidized to Fe(III) upon contact with atmospheric oxygen was determined across the downcore tan–green color change in Peru Basin sediments. This latent fraction of reactive Fe(II) was only found in the green strata, where it proved to be large enough to constitute a deep reaction layer with respect to the pore water O2 and NO3−. Large variations were detected in the proportion of the reactive Fe(II) concentration to the organic matter content along core profiles. Hence, the commonly observed tan–green color change in marine sediments marks the top of a reactive Fe(II) layer, which may represent the major barrier to the movement of oxidation fronts in pelagic subsurface sediments. This is also demonstrated by numerical model simulations. The findings imply that geochemical barriers to pore water oxidation fronts form diagenetically in the sea floor wherever the stage of iron reduction is reached, provided that the sediments contain a significant amount of structural iron in clay minerals.

Description: A coulometrically-based SOMMA system for the determination of total dissolved carbon dioxide (TCO2) in a continuous mode was designed and tested at sea. The new continuous technique approached the same high accuracy and reliability associated with prior discrete TCO2 measurements. During three cruises encompassing more than 19 weeks and 6000 continuous TCO2 measurements none of the three different systems tested exhibited any hardware-related failures. We found that coulometer cell lifetimes can greatly exceed prior expectations with many of the titration cells in the continuous mode remaining accurate for up to 72 h at carbon ages exceeding 50 mg C. We suggest a practical definition based on the CRM analyses for changing coulometer cells in the continuous mode. Systematic deviations of the SOMMA pipette volume from a theoretical temperature dependence were identified both from field data comparisons and pipette calibrations. Hence pipettes should be kept at constant temperature or they must be gravimetrically calibrated over the expected temperature range. Comparison of the continuous TCO2 data together with simultaneously measured additional CO2 system parameters showed that the refitted “Mehrbach” dissociation constants for carbonic acid best-represent fCO2 when calculated from TCO2 and alkalinity over a wide range of sea-surface temperatures and salinities. Some remaining systematic differences of calculated–measured fCO2 of up to 9 μatm likely reflect uncertainty in the temperature-dependence of the “Mehrbach” constants as well as possible uncertainty in the alkalinity–salinity relationship used to estimate alkalinity in the consistency checks.

Description: An unrealistically high-salinity maximum is found to develop in a high-resolution model of the north and equatorial Atlantic below the shallow halocline in the Gulf of Guinea. The spurious water mass with salinities too high by as much as 1 psu is formed when the vertical advection is treated by the standard central-differencing advection scheme. The problem is considerably reduced either by increasing the vertical resolution of the numerical grid, or by switching to a higher-order upwind-weighted scheme for vertical advection. This note stresses the need for a careful consideration of vertical discretization even in typical high-resolution ocean general circulation models (OGCMs). Particular attention is needed for studying heat and salt budgets or transports of biogeochemical tracers.

Description: Data on the carbonate system of the Northwestern Indian Ocean obtained on a cruise of F.S. Meteor during SW monsoon in July/August 1995 were compared with those of George et al. [George, M.D., Kumar, M.D., Naqvi, S.W.A., Banerjee, S., Narvekar, P.V., de Sousa, S.N., Jayakumar, D.A., 1994. A study of the carbon dioxide system in the northern Indian Ocean during premonsoon. Mar. Chem. 47, 243–254] collected during intermonsoon. In general, deep water values agreed well between the two expeditions. Surface waters, however, showed a substantial increase in dissolved inorganic carbon (CT) in the coastal regions due to strong upwelling in the SW monsoon. This was also accompanied by very high CO2 partial pressures in surface waters. The north–south gradients in vertical profiles of the measured parameters in the Arabian Sea are discussed by comparing profiles from the oligotrophic equatorial region with those from the highly productive central Arabian Sea. The effect of denitrification on regenerated CT and AT is minor, with contributions of 〈9 and 〈8 μmol kg−1, respectively, to the total amount regenerated also utilizing oxygen. The dissolution of biogenic carbonates is discussed; different approaches to define the depth, where the dissolution starts (lysocline(s), carbonate critical depth (CCrD)), are compared together with the calculation of saturation depth from carbonate concentrations. It is shown, that small differences in measured CT and AT (found between our data and those measured during GEOSECS) and different calculation approaches to the CO2 system (different dissociation constants for species involved and taking into account phosphate and silicate concentrations) can produce pronounced differences in the calculated saturation depths. However, CT and AT data suggest substantial dissolution of biogenic carbonate in the water column even above the calcite lysocline, irrespective of the procedures followed to calculate this horizon.

Description: We compare the time series of major element geochemical and Pb- and Nd-isotopic composition obtained for seven hydrogenous ferromanganese crusts from the Atlantic, Indian, and Pacific Oceans which cover the last 60 Myr. Average crust growth rates and age-depth relationships were determined directly for the last about 10 Myr using Be-10/Be-9 profiles. In the absence of other information these were extrapolated to the base of the crusts assuming constant growth rates and constant initial Be-10/Be-9 ratios due to the lack of additional information. Co contents have also been used previously to estimate growth rates in Co-rich Pacific and Atlantic seamount crusts (Puteanus and Halbach, 1988). A comparison of Be-10/Be-9- and Co-based dating of three Co-rich crusts supports the validity of this approach and confirms the earlier chronologies derived from extrapolated Be-10/Be-9-based growth rates back to 60 Ma. Our data show that the flux of Co into Co-poor crusts has been considerably lower. The relationship between growth rate and Co content for the Co-poor crusts developed from these data is in good agreement with a previous study of a wider range of marine deposits (Manheim, 1986). The results suggest that the Co content provides detailed information on the growth history of ferromanganese crusts, particularly prior to 10-12 Ma where the Be-10-based method is not applicable. The distributions of Pb and Nd isotopes in the deep oceans over the last 60 Myr are expected to be controlled by two main factors: (a) variations of oceanic mixing patterns and flow paths of water masses with distinct isotopic signatures related to major paleogeographic changes and (b) variability of supply rates or provenance of detrital material delivered to the ocean, linked to climate change (glaciations) or major tectonic uplift. The major element profiles of crusts in this study show neither systematic features which are common to crusts with similar isotope records nor do they generally show coherent relationships to the isotope records within a single crust. Consequently, any interpretation of time series of major element concentrations of a single crust in terms of paleoceanograghic variations must be considered with caution. This is because local processes appear to have dominated over more basin wide paleoceanographic effects. In this study Co is the only element which shows a relationship to Pb and Nd isotopes in Pacific crusts. A possible link to changes of Pacific deep water properties associated with an enhanced northward advection of Antarctic bottom water from about 14 Ma is consistent with the Pb but not with the Nd isotopic results. The self-consistent profiles of the Pb and Nd isotopes suggest that postdepositional diagenetic processes in hydrogenous crusts, including phosphatization events, have been insignificant for particle reactive elements such as Pb, Be, and Nd. Isotope time series of Pb and Nd show no systematic relationships with major element contents of the crusts, which supports their use as tracers of paleo-seawater isotopic composition

Description: Variations of intensity and composition of biogenic particle flux at the northern boundary of the present PolarFrontal Zone in the Atlantic sector of the Southern Ocean are indicators of major changes of paleoenvironmentalconditions on glacial/interglacial time scales during the Late Quaternary. In order to estimate those pastchanges, sediment accumulation patterns of two piston cores, one from just north and one just south of thepresent day position of the Subantarctic Front were reconstructed. Using the 230Thex method large contributionsof laterally supplied material were quantified and used to correct sediment accumulation rates. During the lastglacial focussing of biogenic opal-dominated material exceeded the original contribution from the surfacewater above by a maximum factor of 8.7. The initial activity ratio of 231Paex/230Thex was used as tracer forbiogenic particle flux and composition and indicates that during the glacial stages 2 and 4 the area of high opalproductivity was situated above the location of the southern core whereas the northern core has not beenreached by this northward shift during the last 130 kyr as shown by the pattern of focussing-corrected bulkaccumulation rates. If the position of the Antarctic Polar Front has remained at the northern boundary of thehigh opal productivity area during the last 130 kyr, the results suggest that was located exactly between thetwo core sites during glacial stages 2 and 4. A two-box modeling approach involving particle flux and boundaryscavenging intensity of 231Pa was applied to estimate the possible range of the 231Paex/230Thex ratio recordedin Southern Ocean sediments. Previous estimates on the export of 231Pa from the Atlantic into the SouthernOcean are corroborated but the model suggests a low sensitivity of the 231Paex/230Thex ratio in Southern Oceansediments to variations of the residence time of North Atlantic Deep Water in the Atlantic Ocean.

Description: At Aqaba in the Northern Gulf of Aqaba, Red Sea, the stable oxygen isotope record of a Por#es lutea coral colony was studied. From a vertical and a horizontal core two parts from the base of the colony (10 years of coral growth), and two parts from the living surface (12 years of coral growth) were analysed with a monthly sampling resolution. The results show that seasonality of sea surface temperatures (SST) in the northem GulfofAqaba has increased since the early 19th century, mainly due to higher summer temper- atures. 8~80-ratios indicate that SST increased by at least 1.3~ Horizontal and vertical cores display dif- ferent variations in the modern parts, probably caused by the very shallow water depth of the youngest part of the vertical core.

Description: Tens of thousands of synthetic substances are in existence today and hundreds of new compounds are being introduced every year. Because of the complexity of the physico-chemical interactions between pollutants and the marine environment, the potential toxicity of contaminants can be assessed adequately only by means of bioassays with living organisms. From a practical point of view, a bioassay needs to be sensitive and scientifically valid, yield rapid results at moderate cost, and the organism in question must be readily available. Ecotoxicological bioassays with bivalve embryos and larvae fulfil these criteria better than most other tests. They have increasingly come into use during the past three decades and are now commonly employed to ascertain the biological effects of pure chemicals, as well as to determine the quality of effluents, coastal waters and sediments sampled in the field. There do not appear to be very great differences between bivalve species with regard to larval sensitivity to toxicants. The principal species for bioassays are oysters (Crassostrea gigas and C. virginica), and mussels (Mytilus edulis and M. galloprovincialis). Bioassays are conducted with gametes and larvae of ail ages: sperm and unfertilized eggs, embryos, young D-larvae, intermediate umboned larvae, and pediveligers towards the end ofthe pelagic period. Embryos are usually the most sensitive stage. Recent advances now also permit bioassays on metamorphosing pediveligers, a method particularly suited to investigate the effects of adsorbate-contaminated surfaces. There are various criteria for the assessment oftoxic effects, including embryogenesis success (abnormalities), larval growth, mortality, physiology (e.g. feeding or swimming activity), and metamorphosis success. Chronic toxicity studies may be carried out over periods ofseveral weeks, but larval rearing in the laboratory requires considerable effort (e.g. cultivation of algal food). The method of choice for investigations of acute toxicity and for routine monitoring studies is the embryo bioassay because it is very sensitive, relatively simple, and produces results within 24 or 48 hours. The data obtained by different investigators are often difficult to compare, however, because of differences in methodology. There is no firmly established procedure, and further simplification and standardization of techniques is required. In bioassays with a single pollutant, the effective toxic concentration may span several orders of magnitude, depending on bioassay procedures, larval stage and choice of response. Tributyl-tin (TBT) is the most toxic compound ever bioassayed with bivalve larvae, with effective concentrations (EC50) as low as a few nanograms per litre (i.e. 10−3 ppb). Heavy metals (particularly mercury, silver and copper) are next in order of toxicity, with EC50 values between a few micrograms per litre (ppb) and several hundred ppb. Chlorine and some organochlorine pesticides may also have EC50 values of less than 100 ppb, while detergents and petroleum products are generally less toxic

Description: Sensitivities of cirrus cloud radiative forcing as well as solar albedo and infrared emittances to ice crystal size spectrum and ice crystal shape were examined using a coupled cloud-radiation model. The single- and bi-modal crystal size distribution were considered and simulated based on field measurements. Optical parameters of ice crystals shaped as hexagonal columns and random polycrystals (being frequently found in cirrus clouds) were calculated with a ray-tracing method. Both solar and infrared cirrus radiative forcing are influenced by the pattern of crystal size spectra. The net radiative forcing is lower for bi-modal than for single-modal spectra. The solar radiative forcing of cirrus cloud is reduced by nonspherical ice crystals, due to larger albedo effects of nonspherical crystals compared to those of equivalent spherical crystals. Moreover, this reduction in solar radiative forcing by random polycrystals is even larger than that by hexagonal column crystals. The cloud radiative forcing, solar albedo and infrared emittance are changed significantly as the mean crystal size approaches the smaller size end. Furthermore, net cloud radiative forcing is positive in most cirrus cases. Exceptions are cirrus clouds with a large number (〉107 m−3) of small (mean maximum dimension 〈30 μm) ice crystals and cirrus clouds with bi-modal crystal size distribution and large particle size for the second maximum peak.

Description: Repeatable species dominance patterns across nutrient ratio gradients are found both in culture competition experiments and in natural waters. However, the mechanisms behind these similar patterns need not to be identical. In chemostat experiments, such patterns are caused by the two-way competitive interactions between contemporaneously occurring organisms. Nutrient competition may be important in situ too, but there is an additional effect of early successional species influencing the nutrient environment for later successional species, without being influenced themselves by their successors.

Description: Colonization of new habitats, which have been established as a result of a catastrophic disturbance of the environment, is one of the characteristic repetitive events throughout the Phanerozoic. In recent years, much attention has been paid to investigations focusing on biological recovery of benthic habitats severely disturbed by human activity. In order to improve our environmental and stratigraphical interpretations of such events, we need a more thorough understanding of the processes involved in colonization by one of the most abundant and useful fossil groups, the benthic foraminifera. The present review focuses on processes governing benthic foraminiferal dispersion and colonization patterns in modern environments. For benthic foraminifera, the only active dispersal mechanism is through self-locomotion on or within the sediment and this is considered to be efficient over short distances only. Several passive dispersal methods have been suggested but two seem to be of more general importance. These are dispersal through release and transport of embryonic juveniles and passive suspension and transport of various growth stages. Both are probably important for most benthic foraminifera but the former is likely to be the main mechanism for attached, tubular and larger foraminifera, which are not easily entrained at a later life stage. The latter seems to be a more important dispersion mechanism for benthic foraminifera than previously realized. The colonization rate of soft-bottom substrates is closely related to the hydraulic regime in, and the transit time from, the source area inhabited by species capable of colonizing the new habitat (as long as food and other environmental characteristics are not limiting factors). The transit time depends on the speed of the transporting medium and the distance from the source area. There seems to be two end-processes which can operate during the colonization, depending on whether physically induced or biological processes are allowed to dominate. They are characterized by different colonization patterns. In high energy environments (bottom current velocities often 〉20 cm/s), a short transit time may cause the major components of the nearest ambient seafloor assemblages to colonize the new habitat within days. In this case the colonization is simply through a physical transfer of parts of the source community to the new habitat, allowing no time for pioneer, opportunistic assemblages to develop. In low energy environments (bottom current velocities generally 〈10 cm/s), the transit time is long for most species. Here, colonization follows the classic metazoan successional pattern with an initial, high abundance pioneer assemblage strongly dominated by small opportunists followed by development of assemblages with increasing numbers of specialized species and recovery can take from one to several years. Initial lack of food (e.g., volcanic ash) or `hostile' substrate properties (e.g., recently reoxygenated or severely contaminated sediments) may delay colonization by months or even years. Small, infaunal species (both calcareous and agglutinated) are among the first and most successful colonizers of soft bottom habitats from shallow waters to the deep sea. Throchospiral agglutinated taxa are among the most abundant colonizers on deep sea hard substrates.

Description: The excretion of siderophores and the reduction of organic iron-complexes at the cell surface are common reactions of terrestrial plants, fungi and bacteria in response to low availability of iron. However, there is much less evidence for the use of these strategies by marine phytoplankton. It has been argued that siderophore excretion is inefficient in an aquatic environment due to rapid diffusion. This study examines how diffusion and chemical reactions in the microenvironment of a phytoplankton cell influence the efficiency of both strategies to increase the bioavailability of iron and to reduce iron stress. A numerical model of the cell surroundings is presented that calculates the concentration distribution for different iron species and allows to study the effect of siderophores or surface reductases. It calculates the efficiency of these mechanisms, defined as the quotient between the increase in iron uptake rate and the excretion rate of siderophores or electrons, needed to obtain this increase. The dependence of this efficiency on rates of iron coordination reactions, on diffusivity, and on the kinetics of iron uptake is discussed with the aid of some analytical calculations.

Description: Laboratory feeding experiments were conducted to elucidate size-relationships in the seastar-mussel (Asterias rubens-Mytilus edulis) predator-prey interaction. This is one of the most well-known predator-prey relationships in marine benthic ecology and the dependence of seastar feeding rates and prey size selection are crucial for modelling. Moreover, the hypothesis should be tested that large individuals of M. edulis enjoy a size-refuge from seastar predation in the Baltic sea. Ingestion rates showed an allometric relationship to seastar size. They increased slightly more than cubically (b = 3.62) with the linear size of the seastars and slightly more than linearly (b = 1.27) with the body mass of the seastars. Somatic growth rates were linearly related to ingestion rates. Larger seastars tended to eat larger mussels. This relationship was significant for the largest size of mussels eaten and for the mean size of mussels eaten, but not for the minimal size. Size selection of seastars did not depend on the spatial arrangement of mussel sizes relative to the initial position of the seastars in the aquarium. Mussels of 〉 48 mm in length are safe from predation by the largest seastars found in the western Baltic sea.

Description: The (87)Rb/(86)Sr and (87)Sr/(86)Sr ratios of Laptev Sea sediments, of Arctic Ocean sediments and of suspended particulate matter (SPM) from Siberian rivers (Lena and Khatanga) form 'pseudo-isochrons' due to grain-size separation processes which are referred to as 'Lena Mixing Envelope' (LME) and as 'Flood Basalt Envelope' (FBE). At the land-ocean transition the reduction of the particle velocity causes a deposition of coarser grained material and the contact with saline water enhances a precipitation of finer-grained material. The coarse-grained material is enriched in Sr showing less radiogenic (87)Sr/(86)Sr ratios whereas fine grained material is depleted in Sr relative to Rb showing more radiogenic (87)Sr/(86)Sr ratios, The experimentally determined spread of the (87)Rb/(86)Sr and (87)Sr/(86)Sr ratios as a function of grain size in one sediment sample is on the same order as the natural spread of the (87)Sr/(86)Sr ratios observed in all samples from the Arctic Ocean. Chemical Index of Alteration (CIA) for the Lena river SPM tend to confirm previous observations that chemical alteration is negligible in the Arctic environment. Thus, these 'pseudo-isochrons' reflect an average age and the average isotope composition in the river drainage area. Calculated apparent ages from the FBE reflect the age of the Siberian flood basalt of about 220 Ma and the initial ratio of 0.707(1) reflects their mantle origin. The age calculated from the LME of about 125 Ma reflects accidentally the Jurassic and Cretaceous age of the sediments drained by the Lena river and the initial ratio of 0.714(1) reflects the crustal origin of their source rocks. Comparison of geographical locations reveals that all samples from the eastern Laptev Sea (east of 120 degrees E) fall along the LME whereas all samples from the western Laptev Sea (west of 120 degrees E) fall between LME and FBE. Mixing calculations based on (143)Nd/(144)Nd measurements, not influenced by grain size, show that about 75% of the western Laptev Sea sediments originate from the Lena drainage area whereas about 25% of the sediments are delivered from the Siberian flood basalt province. Sediments from the central Arctic Ocean are isotopically related to the Lena drainage area and the Siberian flood basalt province. However, sediments from the Arctic Ocean margins close to Novaya Semlya, Greenland, the Fram Strait and Svalbard originate from sources not yet identified. (C) 1999 Elsevier Science B.V. All rights reserved.

Description: The effect of the supply of chlorinated biphenyls by the river Oder into some adjacent areas of Baltic Sea was studied in nine sediment cores and in 10 suspended matter samples. Congener-specific analysis was carried out on 28 individual chlorobiphenyls (CBs). ∑CB concentrations in suspension ranged from 2.4 pg dm-3 in the southern Bornholm Basin to 986 pg dm-3 in the Achterwasser. ∑CB contents in surface sediment decreased with increasing distance from the river mouth. Highest contents were found in the Oderhaff (18 ng g-1 dw) decreasing to 2 ng g-1 dw in the Bornholm Basin. The ∑CB contents generally decreased more or less regularly with increasing depth. The compositions of the CB mixtures in surficial sediment and suspension samples were rather similar, suggesting a common source. Compositions of the CB mixtures in the sediment cores showed distinct differences. These may reflect variations in source strength over time. Mass balance considerations on the basis of the 28 CBs resulted in an estimation of a total storage of approximate 733±158 kg ∑CBs in the Oderhaff, Achterwasser, Greifswalder Bodden, Oder Rinne, Arkona Basin and Bornholm Basin in the past 65 years, covering the time period since CBs were first produced. Based on river data about 500 kg of ∑CBs were supplied during this time by river Oder, that may thus be the major source of these compounds for the southern Baltic Sea.

Description: Individual chlorinated biphenyls (CBs) and chlorinated pesticides (p,p′-DDT and metabolites, HCHs and HCB) were determined in blubber samples of 40 harbour porpoises (Phocoena phocoena) of different age and sex from the North Sea, the Baltic Sea and Greenland coastal waters. Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) were analysed in a selected group of animals. ΣCB concentrations (medians) in North Sea immature specimens were similar (14.9 μg/g lipid) to those from the Baltic Sea (17.0 μg/g lipid) and exceeding those in Greenland specimens by an order of magnitude (1.3 μg/g lipid). The median concentrations (μg/g lipid) of HCB, p,p′-DDE, p,p′-DDD and γ-HCH were in the order Greenland〈North Sea〈Baltic Sea. The highest concentrations of α-HCH (0.14 μg/g lipid) were found in the Greenland population, and p,p′-DDT was detected only in this group. The North Sea and Baltic Sea populations were identified as distinctly separate on the basis of levels and compositions of these contaminants. The ecological risk associated with dioxin-like toxicity was dominated by the CB congeners 118 and 170; the PCDD/Fs were playing only a minor role.

Description: Progress in marine chemistry has been driven by improved sampling and sample handling techniques, and developments in analytical chemistry. Consequently, during the last 20 years our understanding of marine trace metal biogeochemistry has improved a great deal. Stripping voltammetric techniques (anodic stripping voltammetry and adsorptive cathodic stripping voltammetry) have made an important contribution to this understanding. The selectivity and extremely low detection limits have made stripping voltammetry a widely used technique for trace metal speciation and trace metal distribution measurements in seawater. Stripping voltammetry is very suitable for ship-board and in-situ applications because of the portability, low cost and capability for automation of the voltammetric instrumentation. Future developments in stripping voltammetry can be expected in the field of stand-alone submersible voltammetric analysers, capable of continuous trace metal measurements. Future applications of stripping voltammetry can be found in the interactions between trace metal speciation and growth and the functioning of organisms in pristine and metal polluted marine waters. Copyright (C) 1999 Elsevier Science B.V.

Description: The distribution of trace metals was determined in coastal waters around England during cruises in December 1993 (CH108), October 1994 (CH115), January 1995 (CH117) and April 1995 (CH118). Cu and Ni distributions were pronouncedly influenced by mixing of river waters with seawater during CH108 coinciding with seasonally enhanced freshwater inputs, but less so during the subsequent cruises. These seasonal variations indicate the importance of processes other than conservative mixing on the distributions of Cu and Ni: benthic and atmospheric inputs, removal by biological uptake and particle scavenging. This paper is one of the first to report on coastal dissolved Cr distributions. Non-conservative behaviour was observed for Cr (CH108), with generally low concentrations which were attributed to particle scavenging. Dissolved Zn exhibited a non-conservative behaviour during the spring and late summer cruises, suggesting that processes other than mixing between water masses was influencing its behaviour. Co showed non-conservative behaviour during the late summer cruise (CH115), which was attributed to the influence of benthic inputs and particle scavenging on its distribution.

Description: Two new neo-clerodane type diterpenoids, teulolin A (15,16-epoxy-6,7,18,19-tetrahydroxy-neo-cleroda-3(4),13(16),14-trien-20, 12(S)-olide, 1) and teulolin B (15,16-epoxy-3α, 6,7,18,19-tetrahydroxy-neo-cleroda-4(18),13(16),14- trien-20,12(S)-olide, 2) were isolated from the aerial parts of Teucrium polium. The structures of 1-2 were proposed on the basis of extensive NMR experiments and molecular modeling studies

Description: Nutrient (nitrate, phosphate, silica) and dissolved metal (Al, Cu, As, Cd, Ni, Zn, Fe, U) distributions were studied in the mixing zones of the Tinto and Odiel rivers which drain the South Iberian pyrite belt. Phosphate distribution is strongly influenced by discharges from the fertiliser industry, especially in the Tinto mixing zone. The increase of silica content in this zone is related to a release of biogenic silica from diatoms. Nitrate concentrations which are influenced by urban and industrial effluents showed an important maximum in the early stages of mixing in the Tinto (as do the metals). Compared to the Odiel river, the metal concentrations in the Tinto river reached higher values in relation to more intensive mining activities. Dissolved Fe, Mn, Al, Cu, Cd and Zn concentrations were correlated in the mixing zones of both rivers. This suggests that they have the same source and are subjected to the same controlling processes in the estuary. A maximum concentration for these metals was observed in the early stage of mixing in the Tinto and reflects a decrease of redox in a low pH (〈3) environment. Downstream in the Odiel system, metals showed a slight removal. Dissolved uranium, present at a low level (0.05 μmol l-1) in the rivers, is introduced by the phosphate fertiliser industry in the estuary and trapped in sedimentation areas. As a consequence, waters of the Gulf of Cadiz have a U content similar to that of the open seawater. Copyright (C) 1999 Elsevier Science B.V. All rights reserved.

Description: Sorption of trace metals by suspended particulate matter (SPM) in estuarine systems has important implications for the fate of dissolved metals in these waters. This paper describes the development of a single extraction procedure for SPM-associated trace metals, using a ligand competition approach with EDTA as the added complexing ligand. The use of EDTA allows the determination of available particulate trace metals using well defined constraints with respect to the competition for trace metals between EDTA and the particles. Incubation experiments showed that equilibrium times between EDTA and particulate material of 72h were required to reach equilibrium for most of the metals studied (Cu, Zn, Mn, Ni, Co, Al, Fe, Pb and Mg). Optimum conditions included a 0.05M EDTA concentration and the use of an extractant: particulate matter ratio of 200:1 (v:w). Kinetic calculations on data from the incubation experiments were used to calculate the apparent stability constants (K(MeS)) for the metal-particulate matter interaction and indicated values ranging from 10-2.1 for K(MgS) to 10-13.5 for K(CuS). Copyright (C) 1999 Elsevier Science B.V.

Description: On April 25, 1998, a spill at the Los Frailes mine in southern Spain resulted in a very high input of metals (including Ag, As, Cd, Cu, Fe, Pb, Tl and Zn) into the river Guadiamar. Calculations indicate that the discharges into the Guadiamar of Cu (5100t), Pb (24,700t), Zn (26,200t) and Ag (138t, based on mud only) were higher than the annual production by the Los Frailes mine for Ag and Pb, and ca. two times less for Cu and Zn. For many metals, the increase in concentration in the affected river (Guadiamar), 2days after the initial discharge, was by several orders of magnitude. However, 6months after the incident, no evidence of the spill could be observed in the plume of the river (Guadalquivir) which discharged the mine waters into the coastal waters of the Gulf of Cadiz. This observation can possibly be explained by low rainfall, natural metal removal processes in the river and estuarine environments and by human interventions. Copyright (C) 1999 Elsevier Science Ltd. On April 25, 1998, a spill at the Los Frailes mine in southern Spain resulted in a very high input of metals (including Ag, As, Cd, Cu, Fe, Pb, Tl and Zn) into the river Guadiamar. Calculations indicate that the discharges into the Guadiamar of Cu (5100 t), Pb (24,700 t), Zn (26,200 t) and Ag (138 t, based on mud only) were higher than the annual production by the Los Frailes mine for Ag and Pb, and ca. two times less for Cu and Zn. For many metals, the increase in concentration in the affected river (Guadiamar), 2 days after the initial discharge, was by several orders of magnitude. However, 6 months after the incident, no evidence of the spill could be observed in the plume of the river (Guadalquivir) which discharged the mine waters into the coastal waters of the Gulf of Cadiz. This observation can possibly be explained by low rainfall, natural metal removal processes in the river and estuarine environments and by human interventions.

Description: The compositionally zoned San Juan eruption on La Palma emanated from three eruptive centers located along a north–south-trending rift zone in the south of the island. Seismic precursors began weakly in 1936 and became strong in March 1949, with their foci progressing from the north of the rift zone towards its south. This suggests that magma ascended beneath the old Taburiente shield volcano and moved southward along the rift. The eruption began on June 24, 1949, with phreatomagmatic activity at Duraznero crater on the ridgetop (ca. 1880 m above sea level), where five vents erupted tephritic lava along a 400-m-long fissure. On June 8, the Duraznero vents shut down abruptly, and the activity shifted to an off-rift fissure at Llano del Banco, located at ca. 550 m lower elevation and 3 km to the northwest. This eruptive center issued initially tephritic aa and later basanitic pahoehoe lava at high rates, producing a lava flow that entered the sea. Two days after basanite began to erupt at Llano del Banco, Hoyo Negro crater (ca. 1880 m asl), located 700 m north of Duraznero along the rift, opened on July 12 and produced ash and bombs of basanitic to phonotephritic composition in violent phreatomagmatic explosions (White and Schmincke, 1999). Llano del Banco and Hoyo Negro were simultaneously active for 11 days and showed a co-variance of their eruption rates indicating a shallow hydraulic connection. On July 30, after 3 days of quiescence at all vents, Duraznero and Hoyo Negro became active again during a final eruptive phase. Duraznero issued basanitic lava at high rates for 12 h and produced a lava flow that descended towards the east coast. The lava contains ca. 1 vol.% crustal and mantle xenoliths consisting of 40% tholeiitic gabbros from the oceanic crust, 35% alkaline gabbros, and 20% ultramafic cumulates. The occurrence of xenoliths almost exclusively in the final lava is consistent with their origin by wall-rock collapse at depth near the end of the eruption. The volcanic evolution of the 1949 eruption is typical of La Palma eruptions generally. Considerable shallow magma migration prior to and during eruption is manifested by strong seismicity, intense faulting, and the almost unpredictable opening of specific vents which can be spaced three or more km apart.

Description: Processes generating block and ash flows by gravitational dome collapse (Merapi-type pyroclastic flow) were observed in detail during the 1990–1995 eruption of Unzen volcano, Japan. Two different types were identified by analysis of video records and observations during helicopter flights. Most of the block and ash flows erupted during the 1991–1993 exogenous dome growth stage initially involved crack propagation due to cooling and flowage of the dome lava lobes. The mass around the crack became unstable, locally decreasing in tensile strength. Finally, a slab separated from the lobe front, fragmented progressively from the base to the top within a few seconds, and became a block and ash flow. Rock falls immediately followed, in response to local instability of the lobe front. Clasts in these rock falls fragmented and merged with the preceding flow. In contrast, block and ash flows during the endogenous dome growth stage in 1994 were generated due to local bulge of the dome. Unstable lava blocks collapsed and subsequently fragmented to produce block and ash flows.

Description: The Coastal Batholith of central Chile between 31 and 34°S represents a locus of long-lived (c. 200 Ma) plutonic activity. It is composed of four plutonic complexes: Santo Domingo, Limarı́, Papudo–Quintero and Illapel. These complexes, which occur as north-trending discontinuous belts that decrease in age eastward, were emplaced during four major episodes of arc magmatism. The Santo Domingo Complex (Carboniferous) comprises hornblende–biotite bearing tonalites and granodiorites with abundant mafic enclaves, and enclave-free granites. The association of enclave-bearing granitoids and enclave-free granites resulted from different degrees of mixing of crustal- and mantle-derived magmas. The Limarı́ Complex (Lower Jurassic) is a bimodal association of crustal leucogranites and mantle-derived gabbros. The lithology of the Papudo–Quintero Complex (Middle Jurassic) varies from hornblende–pyroxene diorite to biotite granite. The main rock types, namely tonalites and granodiorites, commonly contain mafic enclaves. The granitoids and the enclaves have remarkably similar REE patterns and are similar in Sr–Nd isotope composition, which suggest that they represent a cogenetic suite of mantle origin. The Illapel Complex (Cretaceous) consists of hornblende bearing tonalites, trondhjemites and granodiorites that resemble the rocks of TTG suites. The εNd values and initial ratios (Sri) for the mafic rocks of the Carboniferous Complex (εNd: −2.0 and −3.5; Sri: c. 0.7057) differ markedly from those of the Mesozoic mafic rocks (εNd: +1.9 to +5.4; Sri: 0.7033 to 0.7039), the Cretaceous rocks being the most depleted with regard to Sr–Nd. A change from Carboniferous lithosphere-dominated sources to Mesozoic asthenosphere-dominated sources of the magmas that started in the Early Jurassic is recognized. Slab components can be recognized in the source of the Cretaceous rocks. The crustal source of the Lower Jurassic leucogranites was more isotopically depleted and refractory than that of the Carboniferous granites. On the other hand, no crustal participation in the origin of the Middle Jurassic and Cretaceous felsic granitoids is recognized; they are differentiated from mantle-derived magmas. Progressive removal of old lithospheric mantle during the Mesozoic due to a process of lithospheric delamination would explain the profound change in the subcrustal source, as well as the melting and modification towards a more refractory nature of the continental crust.

Description: Resolving the time–space (and compositional) evolution of volcanism along long-lived South Atlantic hotspot trails is important to understanding the connection between hotspot volcanism and mantle plumes. 40Ar/39Ar ages are reported here for rocks dredged from a line of five individual seamounts along an ∼290 km northeast to southwest line extending from the vicinity of Saint Helena Island, and also for Circe Seamount. These seamounts were created in a midplate setting and could have formed rapidly (≤1 Myr). The St. Helena Seamount ages reveal a remarkably linear migration rate of volcanism of 20±1 mm/yr for at least the past 19 Myr, which is interpreted as the absolute motion of the African plate. Because this is much slower than estimated for earlier African plate migration it also represents the first evidence based on seamount ages for a significant deceleration (∼33%) of the African plate since at least 19 Ma. However, this change could have occurred as early as 30 Ma when the limited data for the Tristan/Gough hotspot chain are also considered. This deceleration supports a relationship between African plate speed and the upsurge of hotspot volcanism on the African continent at ∼25 Ma. We suggest that the increased number of oceanic African hotspots between ∼19 and 30 Ma points to a link also between major changes in plate motion and the onset and continuation of oceanic hotspot volcanism. Our study supports the assumption that chains of individual, rapidly (?) formed seamounts have considerably more potential of providing clear insights into how mantle plumes interact with overriding lithosphere than do those consisting of uninterrupted, more massive lines of hotspot volcanism.

Description: Cephalopods are highly visual animals; the importance of chemical perception to these complex mollusks is less well understood. In this experiment, ventilation rate was used to measure the perception of chemical stimuli by cultured juvenile cuttlefish. The test tank had opaque sides and top to visually isolate the cuttlefish. A clear bottom permitted direct observation of funnel movements associated with ventilation. Cuttlefish cannot see beneath them when resting on the bottom; trials began once cuttlefish had remained calmly on the bottom for at least 15 min. The chemical stimulus was placed in a tank located upstream from the test tank containing a single cuttlefish; the cuttlefish's ventilation cycles were measured by direct observation. Ventilation rate increased significantly after exposure to ink from a conspecific, water containing food, water containing a conspecific, novel seawater and water that had contained sea turtles, potential predators. Results were obtained despite any background chemicals remaining within the closed sea water system, suggesting findings are probably robust to the conditions cuttlefish would normally experience in the ocean. Results are consistent with those obtained using visual stimuli and extend previous research indicating that cephalopods are capable of using chemical cues to detect salient environmental features.

Description: A total of 6171 specimens of Octopus mimus was collected from the commercial small-scale fishery in northern Chilean waters (off Iquique) between January 1991 and March 1992. The animals were grouped by sex, size and month for modal progression analysis (MPA). Total length of the animals ranged from 24 (66 g) to 107 cm (4358 g) for males and from 28 (63 g) to 115 cm (3714 g) for females. There were no significant differences in the length–weight relationship between sexes except in summer. The size structure of the exploited population of O. mimus is rather complex and MPA indicated six sub-annual cohorts for males and five for females. Instantaneous relative growth rate (G) in total body weight varied from 0.29% to 1.37% d−1 and from 0.23% to 1.78% d−1 for males and females, respectively. Seasonality and water temperature affected G in both sexes. Differences in G among sub-annual cohorts within the same season were found and it was observed that G tended to decrease with size.

Description: Basic biological parameters of cuttlefish, Sepia officinalis, in the English Channel are described from samples of commercial and research vessel landings made between April 1994 and September 1995. There was a significant difference between the length–weight relationship of male and female cuttlefish. Growth of both sexes was rapid and seasonal during the last 12 months of life. Males grew faster than females, and reached larger overall lengths and weights. Most males reached maturity before the start of their second winter, although the testis continued to develop until spawning took place the following spring. Female maturation began later and was more prolonged such that it was completed towards the end of the second winter. Adults of both sexes spawned after the second winter between late March and July. Commercial landings data showed spawning cuttlefish initially arrived on inshore grounds in the western Channel, but slightly later and in greater numbers on the inshore grounds of the middle and eastern Channel. The weight and value of cuttlefish landings made by UK vessels in the Channel increased greatly between the mid 1980s and the mid 1990s such that cuttlefish are now a major part of the earnings for several fisheries. The most important fisheries were the offshore beam trawls, and inshore otter trawls and nets. The exploitation pattern of each fishery is described from quarterly samples of commercial landings taken between April 1994 and March 1996. Each exploitation pattern is shown to be a function of the region fished, the catching gear employed, and the growth and migrations of the cuttlefish population. Some implications for stock management are discussed.

Description: NA and protein concentrations, and the RNA to protein ratio, were measured in four species of cephalopods, to evaluate sources of variation and the potential for using RNA concentration and the RNA to protein ratio as growth indices. In field samples of Loligo forbesi and Eledone cirrhosa, RNA concentrations and the RNA to protein ratio were higher in immature animals than in mature animals. In Loligo forbesi, values were also higher in males than in females and higher in smaller individuals than in large individuals. Both these trends are consistent with expected differences in growth rate, i.e. RNA is higher in faster growing animals. Mature female Eledone cirrhosa, a species in which the female is larger and presumably grows faster, had higher RNA concentrations than mature males. However, no such difference between the sexes was seen for immature E. cirrhosa or Todarodes sagittatus. Methods for transport and maintenance of Loligo forbesi in captivity in the Azores are described. Many of the captive squid showed poor growth and survival but results from these animals nevertheless confirmed that RNA concentrations were higher in males than in females and higher in animals with smaller gonads than in animals with large gonads. Higher protein concentrations were found in males than in females, and protein concentration was also positively correlated with feeding rate and digestive gland indices. Octopus vulgaris held in captivity grew rapidly and consistently and RNA concentrations were lower in bigger animals than in smaller animals. Neither experiment provided direct support for the hypothesis that RNA concentration or the RNA to protein ratio is directly related to growth rate. Systematic variation in protein concentration, e.g. in relation to recent feeding, leads us to suggest that protein concentration (mg/g fresh body weight) is likely to provide a more reliable index than the RNA to protein ratio.

Description: Laboratory rearing of 19 Octopus mimus from 40 to 589 g at 20.1±1.8°C (September to December 1991) provided information on the growth pattern and variation in instantaneous relative growth rate (G) of this Chilean littoral octopus. The three smallest specimens (ranging from 40 to 49.8 g) attained an average weight of 558 g in 70 days. Growth of this species had two phases. Growth was exponential during the first 40 days of culture with an average G of 5.33%. It slowed and became logarithmic when the animals attained weights ranging from 326.6 to 439 g. Instantaneous relative growth rate decreased from 2.25% to 0.99% during the logarithmic phase. A similar pattern was found for the 16 larger specimens (61.4–406.4 g initial weight). The change in growth pattern observed between the exponential and logarithmic phases occurred at body weights ranging from 326.6 to 454.2 g. No differences in growth were found between sexes in O. mimus. The growth pattern of this species is discussed and compared to other small-egged octopus species raised in captivity.

Description: Results are presented from particle flux studies using sediment trap and current meter moorings along a transect at the European continental margin at 49°N within the EU-funded Ocean Margin Exchange (OMEX) project. Two moorings were placed, at the mid- and outer slope in water depths of 1500 and 3660 m, with traps at 600 and 1050 m and at 580, 1440 and 3220 m, respectively. Residual currents at the mid-slope follow the slope contour, whereas seasonal off-slope flow was registered at the outer slope. At 600 m on the slope fluxes are similar to those in the abyssal North Atlantic. The flux of all components (bulk dry weight, particulate organic and inorganic carbon, lithogenic matter and opal) increased with water depth. Highest fluxes were recorded at 1440 m at the outer slope, where off-slope residual currents mediate particle export. The injection of biogenic and lithogenic particles below the depth of winter mixing results in the export of particles from shallower waters. Calculated lateral fluxes of particulate organic carbon exceed the primary flux by over a factor of 2 at 1440 m on the outer slope. Estimated lateral fluxes of suspended particulate matter in the water column and intermediate nepheloid layers at the outer slope are potentially large compared to sinking fluxes measured by sediment traps. A comparison is made of particle flux at three continental margin sites and two sites in the adjacent open North Atlantic, from which it is seen that bulk and organic matter flux increases exponentially with proximity to the shelf break. The percentage contribution of particulate organic carbon to biogenic fluxes increases from a mean of 5.7% in the abyssal N. Atlantic to 13.9% at the continental margins

Description: Effects of moderate hypoxia and oscillating oxygen conditions on growth of European sea bass (Dicentrarchus labrax L.) were investigated. Groups of four to six sea bass (initial weights 40–90 g) were exposed to one of three oxygen regimes (40% air saturation; oscillations between 40–86% with a period of 770 min; 86% as a control) at 22°C and a salinity of 37 for 1 month. All fish survived and gained weight, but relative to the controls, the sea bass exposed to hypoxic conditions consumed significantly less food, exhibited a reduced growth, and had a lower condition factor. Oscillating groups were intermediate, and not statistically distinguishable from either normoxic or hypoxic treatments. Feed conversion efficiency and variation in body size were not significantly affected by oxygen conditions. Growth was correlated with feed intake, suggesting that reduced growth under moderate hypoxic or oscillating oxygen conditions is primarily due to reduced appetite and not a consequence of a decrease in feed conversion efficiency.

Description: We show how to represent changes in the distribution of size and sinking speed of marine particles by a two-parameter model. In contrast to fully size-resolved models, this representation holds promise for constructing ocean biogeochemical models with detailed spatial resolution and seasonally varying sinking speed. We treat the mass and number of particles as separate state variables, each obeying its own conservation law. Average size and sinking speed of particles change as particles aggregate or the largest particles sink out. The distribution of particle sizes is assumed to follow a power law, whose exponent changes as a function of average particle size. Compared to biogeochemical models with constant particle sinking speed, our approach imposes a modest increase in computational cost and produces important effects like more rapid sinking immediately following a phytoplankton bloom. Compared to models that use hundreds of size classes to represent the detailed evolution of particle size distribution, our approach offers a major reduction in computational cost, while maintaining realistic behaviour like the sudden onset of significant aggregation when particles are sufficiently abundant.

Description: Periphyton with different biomass levels were grown in-situ in the Kiel Fjord and used for short-term laboratory experiments to study the grazing of the periwinkle Littorina littorea. Ingestion rates increased with biomass in a saturating function as described by Holling's type II functional response model, with a maximal ingestion rate of ca. 260 μg chlorophyll day−1 for 2 cm periwinkles. The half saturation constant of the ingestion rate was ca. 2 μg chlorophyll cm−2. At subsaturating food levels, L. littorea increased the area grazed per time but not intensity of grazing within that area. L. littorea is a moderately selective periphyton grazer. It fed on all algal species present, but the tube-dwelling diatoms Amphipleura rutilans and Haslea crucigera suffered significantly smaller grazing losses than the other species. However, the relative protection of those diatoms against periwinkle grazing decreased with higher biomass and with a higher load of easily ingestible epiphytes.

Description: The Mediterranean Sea has been investigated intensively since the early nineties, using modern techniques and collaborative approaches. This overview summarizes some of the resulting advances that were made concerning the physical oceanography of the western Mediterranean. The water mass formation processes are now much better understood and have been quantified to a large extent. The boundary conditions of the system in terms of surface fluxes and strait transports can be determined with improved accuracy, thus enabling future investigation of interannual variability. The dynamics of the surface and intermediate layers have revealed a variety of eddy and mesoscale processes that are important for the circulation and spreading of water masses. The deep circulation is being investigated with Lagrangian techniques (tracers and floats). First results show a large component of the deep water originating from the Tyrrhenian Sea and intense cyclonic and anticyclonic eddy flows.

Description: The aim of this paper is to study the dependence of reflection, absorption, and transmission of light by optically thick, weakly absorbing disperse media on the shape of constituent particles. Single scattering by nonspherical particles is calculated in the framework of the Rayleigh and geometrical optics approximations. The ratio of the average volume to the average surface of particles and their volumetric concentration are kept constant. Thus, the extinction coefficient and the optical thickness of different media under consideration are the same. Calculations are performed for ice particles at wavelengths of 0.645, 1.24, 1.64, and 2.13 μm. The respective refractive indices range from 1.3082–i1.325×10−8 (weak absorption) to 1.2674–i5.65×10−4 (moderate absorption). The radiative characteristics are calculated in the framework of approximate analytical formulae valid for optically thick, weakly absorbing media.