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  • 1
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    Elsevier
    In:  In: Encyclopedia of Geology. , ed. by Elias, S. and Alderton, D. Elsevier, London, pp. 52-59, 8 pp. 2nd edition ISBN 978-0-08-102909-1
    Publication Date: 2021-01-26
    Description: The vast majority of active volcanism that is located at plate boundaries can be easily explained by plate tectonic processes. Intraplate volcanism, which incorporates some of the smallest and largest volcanic events on Earth, cannot be successfully explained by a single process or model. The most volumetrically significant intraplate volcanic events are associated with the arrival of the head of a thermo-chemical anomaly rising from the deep mantle and impacting the base of the lithosphere. This event generates massive and short-lived magmatic activity over a wide area (up to 2000 km across), forming a large igneous province. A long-lived hotspot track can form over the mantle plume tail and is best illustrated by the formation of age progressive volcanic chains, such as the famous Hawaiian-Emperor chain. Millions of smaller solitary volcanic edifices, non-age progressive volcanic chains and provinces, on the other hand, have other potential mechanisms of origin. Potential models comprise decompression melting due to lithospheric extension, destabilization of fusible lithologies in the lithospheric mantle, small scale sub-lithospheric convection, or lithospheric delamination.
    Type: Book chapter , NonPeerReviewed
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  • 2
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    Elsevier
    In:  In: Fundamentals of Tropical Freshwater Wetlands. , ed. by Dalu, T. and Wasserman, R. J. Elsevier, Amsterdam, The Netherlands, pp. 517-547. ISBN 978-0-12-822362-8
    Publication Date: 2021-11-23
    Type: Book chapter , NonPeerReviewed
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  • 3
    Publication Date: 2021-01-08
    Description: Gas hydrates dissociation could induce or trigger submarine landslides, especially in upper continental slopes where hydrates are vulnerable to natural and artificial perturbations. This work investigates destabilization mechanisms of an upper continental slope undergoing hydrate dissociation and identifies spatiotemporal failure modes influenced by characteristics of the overburden above the hydrate-bearing layer (i.e. the hydrate reservoir). A Thermo-Hydro-Chemical coupled numerical model of transient pore pressure induced by hydrate dissociation is coupled with the limit equilibrium slope analysis method to study the spatiotemporal evolution of the potential sliding plane and to calculate the corresponding factor of safety. The results suggest that overpressure generated by the liberated fluid from hydrate dissociation is the primary reason for instability in a gentle marine slope. The study identifies three sliding modes, namely co-melting non-interface sliding, co-melting interface sliding, and post-melting non-interface sliding, depending on the overburden's characteristics, including overburden thickness, permeability, and cohesion. Co-melting non-interface sliding takes place during hydrate dissociation if the hydrate reservoir underlies a thin, pervious and low-cohesion overburden cover. For less permeable and more cohesive overburdens, the potential sliding plane is deeper and co-melting interface sliding could be triggered due to overpressure developed at the reservoir-overburden interface. If the hydrate reservoir is covered by a thick, low-permeability and slightly cohesive overburden, post-melting non-interface sliding could occur after the hydrates are completely dissociated. This failure is delayed, because the gas/water trapped at the interface during hydrate dissociation is insufficient to trigger instability due to very high overburden stresses. However, as the gas migrates upwards over time and encounters a weak zone in the overburden deposits, failure could happen within the overburden deposits even after hydrate dissociation stops. The findings help to improve our fundamental understanding about the destabilization mechanism and failure modes of the continental slopes undergoing hydrate dissociation, and to delineate the vulnerable configurations of the slopes.
    Type: Article , PeerReviewed
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  • 4
    Publication Date: 2021-01-08
    Description: n our daily lives, we consume foods that have been transported, stored, prepared, cooked, or otherwise processed by ourselves or others. Food storage and preparation have drastic effects on the chemical composition of foods. Untargeted mass spectrometry analysis of food samples has the potential to increase our chemical understanding of these processes by detecting a broad spectrum of chemicals. We performed a time-based analysis of the chemical changes in foods during common preparations, such as fermentation, brewing, and ripening, using untargeted mass spectrometry and molecular networking. The data analysis workflow presented implements an approach to study changes in food chemistry that can reveal global alterations in chemical profiles, identify changes in abundance, as well as identify specific chemicals and their transformation products. The data generated in this study are publicly available, enabling the replication and re-analysis of these data in isolation, and serve as a baseline dataset for future investigations.
    Type: Article , PeerReviewed
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  • 5
    Publication Date: 2021-01-08
    Description: A comparison of gouge and hammer coring techniques in intertidal wetland soils highlights a significant effect of soil compaction of up to 28% associated with the widely applied hammer coring method employed in Blue Carbon research. Hammer coring reduces the thickness of the soil profile and increases the dry bulk density, which results in an overestimation of the soil OC stock of up to 22%. In saltmarshes with multiple different soil units, we show that hammer coring is unsuitable for the calculation of OC stocks and should be avoided in favour of Russian or gouge cores. Compaction changes both soil dry bulk density and porosity and we show that resultant radiometric chronologies are compromised, almost doubling mass accumulation rates. While we show that the OC (%) content of these sediments is largely unchanged by coring method, the implication for OC burial rates are profound because of the significant effect of hammer coring on the calculation of soil mass accumlation rates.
    Type: Article , PeerReviewed
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  • 6
    Publication Date: 2021-01-08
    Description: Seagrasses provide multiple ‘ecosystem services' in coastal waters, including carbon sequestration. However, this ‘Blue Carbon’ potential has been only evaluated for certain species from some areas of the world. In this study, we provide initial estimates on the magnitude and local variability of carbon sequestration, as organic carbon stocks, for seagrass meadows of Cymodocea nodosa (Ucria) Ascherson in the oceanic island of Gran Canaria (Canary Islands, Spain, central-eastern Atlantic). Six seagrass meadows were selected; at each meadow, cores inserted up to 30 cm in the seabed were collected in the ‘interior’, ‘edge’ and ‘unvegetated’ bottoms immediately adjacent to seagrass patches. We estimated organic carbon (Corg) pools by means of the Loss of Ignition (LOI) procedure. Overall, larger Corg pools were observed in the ‘interior’ and 'edges' of meadow patches than in adjacent ‘unvegetated’ bottoms. At the meadow-level, Corg pools were not predicted neither by the meadow area, nor by the mean shoot density, or sediment grain fractions. Overall, the total estimated stock was 86.20 ± 19.06 Mg C ha−1. By considering the total potential extension of seagrass meadows across the entire island perimeter, we estimated a total stock of 60.34 Gg of C, for a mean estimated financial value of 919,432.249 € (1313.47 € ha−1), which ranges between 351,631.35 € (502.33 € ha−1) and 1,498,954.45 € (2141.36 € ha−1), according to varying market prices in the last 5 years. This work highlights, therefore, the importance of meadows underpinned by C. nodosa not only at an ecological, but also at an economic level, in particular from the perspective of regional climate change adaptation strategies.
    Type: Article , PeerReviewed
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  • 7
    Publication Date: 2021-01-08
    Description: Ciona intestinalis is within the group of taxa that are spreading globally and is one of the most thriving invasive marine species, known to depress both species richness and abundance at a local scale in distinct geographic areas. It is a dominant biofouling agent, associated with the decreasing economic incomes from aquaculture operations around the world. Ciona intestinalis was first observed in 2007 at Straumsvík in Southwest Iceland. The present study was designed to provide general information on its current distribution across Icelandic harbours. The species was found only on the SW coast of Iceland, in dense aggregations reaching up to 876 ind/m2 in all harbours from Grindavík to Akranes. The current work provides information that can be used to track the dispersal of C. intestinalis populations along the Icelandic coast and for the development of effective management decisions.
    Type: Article , PeerReviewed
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  • 8
    Publication Date: 2021-01-08
    Description: Interest in microalgae-derived products is growing, mostly due to their unique characteristics and range of industrial applications. To obtain different products, one must employ specific pretreatments that retain the properties of the biologically active compounds extracted from microalgae biomass; thus, new extraction techniques require frequent upgrades. Due to increased interest in economically viable and ecologically friendly processes, new extraction methods that can be incorporated into microalgae biorefinery systems have become the main focus of research. Therefore, this review aims to address the potential applications, future prospects, and economic scenario of the new physicochemical treatments used in the extraction of bioactive microalgae compounds.
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  • 9
    Publication Date: 2021-01-08
    Description: Long-chain polyunsaturated fatty acids (LC-PUFAs) especially ω-3 fatty acids provide significant health benefits for human beings. However, ω-3 LC-PUFAs cannot be synthesized de novo in mammals. Traditionally, ω-3 LC-PUFAs are extracted from marine fish, and their production depends on sea fishing, which has not met ever-increasing global demand. To address the challenges, innovative cellular engineering strategies need to be developed. In nature, many fungi and microalgae are rich in ω-3 LC-PUFAs, representing promising sources of ω-3 LC-PUFAs. The latest progress in developing new cellular engineering strategies toward sustainable ω-3 LC-PUFAs production using fungi and microalga has demonstrated that they can to some extent address the supply shortage. In this review, we critically summarize the recent progress in enhancing the productivity in various ω-3 LC-PUFAs-producing organisms, as well as the latest efforts of biosynthesizing PUFAs in heterogenous biosystems. In addition, we also provide future perspectives in developing genetic toolkits for LC-PUFAs producing microbes so that cut-edging biotechnology such as gene stacking and genome editing can be further applied to increase the productivity of ω-3 LC-PUFAs.
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  • 10
    Publication Date: 2021-01-08
    Description: Factors affecting carotenoid extraction with edible oils were examined using edible brown seaweed, Sargassum horneri, as main sample. The results indicate that drying was essential to extract fucoxanthin (Fx) from S. horneri and physical (boiling) and chemical (acid/alkali) pretreatment of the wet sample increased the extraction rate of Fx. Additionally, more Fx was found from the dried S. horneri powder with a smaller particle size. The extraction rate of Fx is affected by the extraction temperature and time, showing that the effective extraction would be obtained at 50 °C within 12 hr extraction. Among the oils used, short-chain (C4 and C6) triacylglycerol (TAG) (SCT) and medium-chain (C8) TAG (MCT) could extract more Fx from S. horneri and more β-carotene and lutein from spinach and olive leaves. The relatively lower viscosity of SCT and MCT would be the most likely reason for the higher extraction rates of both TAGs.
    Type: Article , PeerReviewed
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  • 11
    Publication Date: 2021-01-08
    Description: Sargassum fusiforme polysaccharides, acidic water-soluble polysaccharides extract from Sargassum fusiforme, are mainly composed of alginic acid, fucoidan and laminaran. Alginic acid is carboxyl-containing polysaccharide formed by joining β-D-mannuronic acid and α-L-guluronic acid through β-(1→4)/α-(1→4) glycosidic bond. Fucoidan, a natural water-soluble sulfated heteropolysaccharide with fucose and sulfuric acid groups as the core structure, is mainly linked by L-fucose through α-(1→3) glycosidic bond and has the strongest biological activity. Laminaran is mainly composed of β-D-glucose through β-(1→3) glycosidic bond linkage. Sargassum fusiforme polysaccharides have a variety of pharmacological activities, including antioxidant, anti-tumor, promoting immunity, anti-aging, prompting bone growth, lowering blood glucose, anti-coagulation, anti-virus, anti-bacteria, anti-fatigue, promoting growth and development, and skin protection. These activities are closely related to the functions of fucoidan in Sargassum fusiforme polysaccharides, which fucoidan is able to strengthen immune system and antioxidation in human body. In this review, the composition, the isolation and purification, and the biological activities of Sargassum fusiforme polysaccharides are discussed and can bereference for further study.
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  • 12
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    Elsevier
    In:  Computers and Geotechnics, 124 (Article number 103596).
    Publication Date: 2021-01-08
    Description: Numerical simulation is important for practical and efficient assessment of hydrate reservoir formation stability and gas production potential. The history-matching simulation of hydrate gas production tests is complex due to coupled THM (thermo-hydro-mechanical) phenomena. The well log data from the Eastern Nankai Trough methane gas production site suggest vertically heterogeneous field properties. In the previous numerical simulation research of this site, the heterogeneous geological data were homogenized by adopting the standard mean-field theory, which can potentially lead to inaccurate simulation results due to the mesh size effect. By introducing new upscaling techniques for the permeability profiles and mechanical responses, a revised homogenization approach is proposed to improve the coupled THM simulation accuracy. In this study, seven gas production simulations of a hypothetical reservoir, six simulations of the Eastern Nankai Trough gas production test, and four simulations of the randomly generated site formation production test with different mesh sizes and different homogenization approaches were carried out to demonstrate that the proposed upscaling techniques can improve the accuracy of the simulation results with a coarse mesh model. This work, in turn, provides researchers and field engineers a much quicker way to assess the complex geomechanical behaviors of hydrate gas production site.
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  • 13
    Publication Date: 2021-01-08
    Description: Nitrous oxide is an important greenhouse gas and there is a need for sensitive techniques to study its distribution in the environment at concentrations near equilibrium with the atmosphere (9.6 nM in water at 20 °C). Here we present an electrochemical sensor that can quantify N2O in the nanomolar range. The sensor principle relies on a front guard cathode placed in front of the measuring cathode. This cathode is used to periodically block the flux of N2O towards the measuring cathode, thereby creating an amplitude in the signal. This signal amplitude is unaffected by drift in the baseline current and can be read at very high resolution, resulting in a sensitivity of 2 nM N2O for newly constructed sensors. Interference from oxygen is prevented by placing the front guard cathode in oxygen-consuming electrolyte. The sensor was field tested by measuring an N2O profile to a depth of 120 m in the oxygen minimum zone of the Eastern Tropical North Pacific Ocean (ETNP) off the coast of Mexico.
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  • 14
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    Elsevier
    In:  Progress in Oceanography, 186 . p. 102346.
    Publication Date: 2021-01-08
    Description: The ability of consumers to convert ingested carbon into growth is critical for secondary production and trophic transfer. We conducted laboratory experiments to investigate the effect of different prey and concentration on the ingestion rate (IR), egg production rate (EPR) and egg production efficiency (EPE) of the ubiquitous copepod, Acartia tonsa. Experiments were run at several prey concentrations, ranging from 11 to 1132 μgC L–1, of the diatom Thalassiosira weissflogii, the autotrophic dinoflagellate Prorocentrum minimum, the heterotrophic dinoflagellate Oxyrrhis sp., the flagellate Dunaliella tertiolecta, and the bacterivorous scuticociliate Uronema sp. IR increased curvilinearly with concentration for all diets. EPR also increased curvilinearly with increasing food concentration similar to IR, with the exception of the flagellate diet, for which EPR decreased linearly with food concentration. EPR ranked as T. weissflogii 〉 P. minimum 〉 Oxyrrhis sp. = Uronema sp. 〉 D. tertiolecta. IR and EPR were linearly related, except for flagellate diet. The slope of the carbon-based relationship between IR and EPR, the egg production efficiency (EPE), was highest for the diatom (77.5%) and lowest for the scuticociliate (4.2%). Egg production was not correlated to ingestion of the flagellate offered to A. tonsa. We conclude that of the five prey species, the diatom T. weissflogii is the best prey to promote A. tonsa reproduction, to optimize trophic transfer efficiency, and to increase mass cultivation of this species.
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  • 15
    Publication Date: 2021-01-08
    Description: Geochemical patterns in the environment are always the result of certain processes. Therefore, it is essential to decipher a process to properly evaluate the environmental role and potential of chemical elements/compounds. This allows the distinction between natural and anthropogenic influence on elemental concentrations. However, if the compositional nature of geochemical data is neglected, erroneous or misleading conclusions regarding the processes involved are probable. In this study the reconstruction of depositional environments and processes through the Holocene in two sediment cores obtained from submerged sinkholes located on the island of Mljet, Croatia, was performed by taking into account the compositional nature of geochemical, mineralogical and grainsize data. Problems involving compositional data are always multivariate; for example, the concentration of a single element does not carry any interpretative information, as only the ratios between elements do. This has led to the discovery of a large number of geochemical proxies based on elemental ratios, which describe certain environmental conditions and processes involved. Nevertheless, some proxies have been found to be restricted to only some specific environments, thus preventing them from being used in general; therefore, some kind of relation between different proxies is necessary to obtain final conclusions. However, when using simple elemental ratios, those correlations cannot be obtained due to the nature of compositional data. With a sequential binary partition of a compositional vector, orthonormal log ratio (olr) coordinates (proxies) can be constructed. When based on expert knowledge, those proxies fully acknowledge the geochemical properties of the chosen elements with one major difference - that the correlation between newly obtained variables is mathematically well grounded. As a result, the final conclusion is more accurate. In this research, geochemical proxies obtained as a representation in olr coordinates of the elements that are enriched compared to the local soil were used to perform principal component analyses. It helped to unravel the evolution of sedimentary environments. Mineralogical (XRD and heavy mineral data) and grain size analyses supported the conclusions obtained based solely on geochemical data. Furthermore, data analysis suggests that the proxies for redox conditions described in the literature should be used with caution, as their use is somewhat limited.
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  • 16
    Publication Date: 2021-01-08
    Description: New antifungals are increasingly needed due to the emergence of resistant fungal strains. Traditional antifungal assays are laborious and require significant amounts of samples. The present work presents a new proposal to evaluate antifungal activity and antagonism among fungal species, based on experiments of fungal culture and co-culture, 1H NMR profile of fungal culture extracts and chemometrics. In order to develop the work, six axenic cultures of fungi that infested fruits (Fusarium guttiforme, Pestalotiopsis diospyri, Phoma caricae-papayae, Colletotrichum horii, Phytophthora palmivora, and C. gloeosporioides), and co-cultures of all possible combination among them were performed (totalizing 63 experiments). All fungal extracts were evaluated by 1H NMR followed by Principal Component Analyses (PCA) in order to determine spectral dissimilarity among the extracts. Results showed that 1H NMR data evaluated by PCA were capable to predict both antagonism and antifungal activity. Traditional antifungal in vitro assays of active and inactive extracts were also performed in order to prove the prediction made by PCA. The obtained data showed that the approach is an outstanding tool to simultaneously obtain and evaluate bioactive compounds because: it was able to predict the activity of five different extracts in a collection of sixty-three, which would be much more difficult and time consuming if applied randomly; most important antifungal extracts are indicated by PCA; hundreds of traditional in vitro assays are avoid; and, the method is very time and money saving.
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  • 17
    Publication Date: 2021-01-08
    Description: Highlights • Total modeled carbon cycling at disturbed sites is lower than at reference sites. • Projected microbial loop functioning is reduced 26 years after sediment disturbance. • Estimated faunal respiration has recovered from sediment disturbance. • Estimated microbial respiration has not recovered from the sediment disturbance. Abstract Due to the predicted future demand for critical metals, abyssal plains covered with polymetallic nodules are currently being prospected for deep-seabed mining. Deep-seabed mining will lead to significant sediment disturbance over large spatial scales and for extended periods of time. The environmental impact of a small-scale sediment disturbance was studied during the ‘DISturbance and reCOLonization’ (DISCOL) experiment in the Peru Basin in 1989 when 10.8 km2 of seafloor were ploughed with a plough harrow. Here, we present a detailed description of carbon-based food-web models constructed from various datasets collected in 2015, 26 years after the experiment. Detailed observations of the benthic food web were made at three distinct sites: inside 26-year old plough tracks (IPT, subjected to direct impact from ploughing), outside the plough tracks (OPT, exposed to settling of resuspended sediment), and at reference sites (REF, no impact). The observations were used to develop highly-resolved food-web models for each site that quantified the carbon (C) fluxes between biotic (ranging from prokaryotes to various functional groups in meio-, macro-, and megafauna) and abiotic (e.g. detritus) compartments. The model outputs were used to estimate total system throughput, i.e., the sum of all C flows in the food web (the ‘ecological size’ of the system), and microbial loop functioning, i.e., the C-cycling through the prokaryotic compartment for each site. Both the estimated total system throughput and the microbial loop cycling were significantly reduced (by 16% and 35%, respectively) inside the plough tracks compared to the other two sites. Site differences in modelled faunal respiration varied among the different faunal compartments. Overall, modelled faunal respiration appeared to have recovered to, or exceeded reference values after 26-years. The model results indicate that food-web functioning, and especially the microbial loop, have not recovered from the disturbance that was inflicted on the abyssal site 26 years ago.
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  • 18
    Publication Date: 2021-01-08
    Description: Highlights: • Crystal structure of the malaria parasite lipocalin • Comparative analysis of lipocalin superfamily members in alveolate genomes • Localization of PfLipocalin to the parasitophorous vacuole and food vacuole • Reverse genetics reveal PfLipocalin function in oxidative damage control Summary: Proteins of the lipocalin family are known to bind small hydrophobic ligands and are involved in various physiological processes ranging from lipid transport to oxidative stress responses. The genome of the malaria parasite Plasmodium falciparum contains a single protein PF3D7_0925900 with a lipocalin signature. Using crystallography and small-angle X-ray scattering, we show that the protein has a tetrameric structure of typical lipocalin monomers; hence we name it P. falciparum lipocalin (PfLCN). We show that PfLCN is expressed in the intraerythrocytic stages of the parasite and localizes to the parasitophorous and food vacuoles. Conditional knockdown of PfLCN impairs parasite development, which can be rescued by treatment with the radical scavenger Trolox or by temporal inhibition of hemoglobin digestion. This suggests a key function of PfLCN in counteracting oxidative stress-induced cell damage during multiplication of parasites within erythrocytes.
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  • 19
    Publication Date: 2021-02-08
    Description: Eco-friendly, cost efficient and effective extraction methods have become significant for the industries applying zero waste principles. The two main objectives of this study were; to examine fucoxanthin extraction from wet Phaeodactylum tricornutum using subcritical fluid extraction and to characterize the residual biomass in order to determine the potential application areas. The highest fucoxanthin yield of 0.69 ± 0.05 mg/g wet cell weight was achieved using methanol with solvent-to-solid ratio of 200:1 at 120 rpm, 20 MPa pressure and at 35 °C for 60 min by subcritical extraction. Microscopy images showed that most of the cells were disrupted and intracellular components were effectively released. Based on the results of energy dispersive spectroscopy, biomass contained a mixture of organic molecules including mainly carbon (57–72%), oxygen (26–41%), magnesium (0.6–1.4%) and silica (0.4–1%) (wt%). These results make the residual biomass a potential candidate for various areas such as bioenergy, material sciences and sensor technologies.
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  • 20
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    Elsevier
    In:  Planetary and Space Science, 190 . Art.-Nr.: 105023.
    Publication Date: 2021-01-08
    Description: In a short note of 1998 Davankov questioned the generally accepted notion that the unique features of the planet Earth, namely, the presence of life and atmospheric oxygen are inseparably bonded as a case and effect. Indeed, photosynthesis in terrestrial and aquatic phototrophs simultaneously produces oxygen and carbohydrates in almost equal amounts. Since the degradation of organic matter through burning or rotting also consumes an equivalent amount of oxygen, the total masses of oxygen and organic material must always remain comparable. This correlation for Earth appears to be drastically distorted in favor of oxygen, thus disproving the still widespread delusion of biogenic origin of atmospheric oxygen. Instead, by analyzing more recent data on the balance between oxygen and organics we arrive at the conclusion that radiolysis of water vapors with the preferential dissipation of hydrogen to space, most probably, was the major source of the free and oxidation-spent oxygen. The present review tries to illuminate the most important uncertainties that still remain to be clarified before an interdisciplinary and scientifically-balanced picture on the evolution of Earth gets settled.
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  • 21
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    Elsevier
    In:  In: Sustainable Seaweed Technologies. , ed. by Torres, M. D., Kraan, S. and Dominguez, H. Elsevier, Amsterdam, Netherlands, pp. 613-639, 27 pp. ISBN 978-0-12-817943-7
    Publication Date: 2021-01-11
    Description: The concept of biosorption results from the “passive” (nonmetabolic) interaction of a chemical species with a particle of a biological material. This interaction can be practically exploited, for example, for removal of toxic substances of wastewaters or for the enrichment of a fertilizer with micronutrients. In this work, equilibrium and dynamic data obtained with “low-cost” biomaterials of algal waste or invasive seaweed species have been reviewed and critically analyzed in the context of a circular economy. The concept of a biosorption unit, oriented to the valorization of any solid residual material of algal biomass, can be considered as a real possibility in a biorefinery process; but to accomplish this goal it is necessary that the emphasis on research must definitely move from laboratory scale toward pilot plant assays.
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  • 22
    Publication Date: 2021-01-08
    Description: Carnivorous gelatinous zooplankton (GZ) can be very abundant in marine ecosystems around the globe and exert considerable predation pressures on micro- to macrozooplankton as well as larval and juvenile fish. As these species are in many cases intermediate and top predators, their biomass can be easily evaluated, which could indicate overall food web stability or alteration. There is growing concern worldwide about increasing abundances of GZ species and consequently negative impacts on food webs and human coastal zones activities. In this paper, I present a case study from a shallow Danish cove and a long-term record spanning 29 years (1991–2019) obtained by unconventional means. Jellyfish were collected using horizontal sub-surface net tows in August and September during a summer student class. Sea surface temperature and chlorophyll a concentration were measured in parallel. No clear long-term trend in jellyfish biomass could be seen, whereas the values were highly variable from year to year. This is in contrast with other published Scandinavian long-term GZ time series. Sea surface temperature and chlorophyll a concentration had significant (and interactive) effects on the jellyfish biomass in Kertinge Nor. The scarcity and shortness of GZ long-term series do not allow solid conclusions in most marine ecosystems, so it becomes clear that publishing time series (even with small spatial extent) can contribute to improve the perception of interannual GZ population developments. Thus, I strongly recommend extending monitoring activities, explicitly including GZ taxa, in as many marine ecosystems as feasible.
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  • 23
    Publication Date: 2021-01-08
    Description: This paper describes methods of obtaining improved estimates of long-term sea level trends for the British Isles. This is achieved by lengthening the sea level records where possible, then removing known sources of variability, and then further adjusting for datum errors that are revealed by the previous processes after verification using metadata from archived sources. Local sea level variability is accounted for using a tide and surge model. Far field variability is accounted for using a “common mode”. This combination reduces the residual variability seen at tide gauges around the coast of the British Isles to the point that a number of previously unrecognised steps in individual records become apparent, permitting a higher level of quality control to be applied. A comprehensive data archaeology exercise was carried out which showed that these step-like errors are mostly coincident with recorded site-specific changes in instrumentation, and that in many cases the periodic tide gauge calibration records can be used to quantify these steps. A smaller number of steps are confirmed by “buddy-checking” against neighbouring tide gauges. After accounting for the observed steps, using levelling information where possible and an empirical fit otherwise, the records become significantly more consistent. The steps are not found to make a large difference to the trend and acceleration observed in UK sea level overall, but their correction results in much more consistent estimates of first order (Sea Level Rise) and second order (Sea Level Acceleration) trends over this 60-year period. We find a mean rate of sea level rise of 2.39 ± 0.27 mm yr−1, and an acceleration of 0.058 ± 0.030 mm yr−2 between Jan. 1958 and Dec. 2018. The cleaner dataset also permits us to show more clearly that the variability other than that derived from local meteorology is indeed consistent around the UK, and relates to sea level changes along the eastern boundary of the North Atlantic.
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  • 24
    Publication Date: 2021-01-08
    Description: Fucoxanthin is the major abundant xanthophyll in macro- and micro-algae as a component of photosynthetic light-harvesting complexes for photosynthesis and photoprotection. Nowadays, widespread application of fucoxanthin in food industry, pharmaceutical, and medical purposes are increasing. The current issue attracts the attention of researchers for producing of carotenoid from its natural resources, especially algae. Againts macroalgae, microalgae have rapid growth with the same source of food. In addition, they can grow from variety of situations and environmental conditions to produce a specific biochemical product. Microalgae, e.g. Tisochrysis lutea (T. lutea), can be cultivated under controlled conditions, low cost, and higher concentration of fucoxanthin. This review presents some of nutraceutical effects of fucoxanthin for human health and then, in particular, recent biotechnological developments in bioprocessing of this valuable product including, cultivation, harvesting, extraction, and purification, from T. lutea.
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  • 25
    Publication Date: 2021-01-08
    Description: Pretreatment of microalgal biomass possessing rigid cell wall is a critical step for enhancing the efficiency of microalgal biorefinery. However, the conventional pretreatment processes suffer the drawbacks of complex processing steps, long processing time, low conversion efficiency and high processing costs. This significantly hinders the industrial applicability of microalgal biorefinery. The innovative electricity-aid pretreatment techniques serve as a promising processing tool to extensively enhance the release of intracellular substances from microalgae. In this review, application of electric field-based techniques and recent advances of using electrical pretreatments on microalgae cell focusing on pulsed electric field, electrolysis, high voltage electrical discharges and moderate electric field are reviewed. In addition, the emerging techniques integrating electrolysis with liquid biphasic flotation process as promising downstream approach is discussed. This review delivers broad knowledge of the present significance of the application of these methods focusing on the development of electric assisted biomolecules extraction from microalgae.
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  • 26
    Publication Date: 2021-01-08
    Description: Coastal communities, knowingly or otherwise, rely on seagrasses for their livelihood, recreation and food source, among other services. However, despite its importance, seagrasses are not receiving similar attentions with its adjacent ecosystems, the mangroves, and coral reefs. Because of their role in climate change mitigation, seagrasses along with mangroves and salt marshes (the blue carbon ecosystems) are gaining attention recently. This preliminary study investigates the perception of coastal communities in Eastern Samar, Philippines on seagrasses. The results of the survey show that there is a level of high awareness among respondents to seagrass ecosystem services. Despite that, however, utilization remains low. The level of awareness varies on the type of ecosystem service; for instance, locals have a high awareness of provisioning services while low awareness of cultural services. The survey also included the perceived threats to seagrasses, where damages caused by natural disturbances are identified as the most concerning threat. This may be due to the geographic location of the sites that are frequented by typhoons. The perception potentially indicates depleted resources brought about by mismanagement or overlooking this natural resource. The results provide a more contextualized understanding on how local communities are aware of and interacting with, or the lack thereof, seagrass ecosystems. This could aid local government units (LGUs) and conservation groups in the area to craft practicable and sustainable management plans and threat-specific solutions.
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  • 27
    Publication Date: 2021-01-08
    Description: Simulating complex physical systems often involves solving partial differential equations (PDEs) with some closures due to the presence of multi-scale physics that cannot be fully resolved. Therefore, reliable and accurate closure models for unresolved physics remains an important requirement for many computational physics problems, e.g., turbulence simulation. Recently, several researchers have adopted generative adversarial networks (GANs), a novel paradigm of training machine learning models, to generate solutions of PDEs-governed complex systems without having to numerically solve these PDEs. However, GANs are known to be difficult in training and likely to converge to local minima, where the generated samples do not capture the true statistics of the training data. In this work, we present a statistical constrained generative adversarial network by enforcing constraints of covariance from the training data, which results in an improved machine-learning-based emulator to capture the statistics of the training data generated by solving fully resolved PDEs. We show that such a statistical regularization leads to better performance compared to standard GANs, measured by (1) the constrained model's ability to more faithfully emulate certain physical properties of the system and (2) the significantly reduced (by up to 80%) training time to reach the solution. We exemplify this approach on the Rayleigh-Benard convection, a turbulent flow system that is an idealized model of the Earth's atmosphere. With the growth of high-fidelity simulation databases of physical systems, this work suggests great potential for being an alternative to the explicit modeling of closures or parameterizations for unresolved physics, which are known to be a major source of uncertainty in simulating multi-scale physical systems, e.g., turbulence or Earth's climate.
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  • 28
    Publication Date: 2021-01-08
    Description: Microalgae are a rich source of natural bioactive compounds, e.g. astaxanthin, β-carotene, lutein, and fatty acids (FAs), that are currently in high demand in the market. Conventional extraction methods often produce adverse effects on some of these compounds. Replacing conventional extraction methods with more efficient advanced green technologies that offer greater extracts purity and low environmental impact is therefore a challenging and sought-for target. This review is a comprehensive overview of supercritical fluid (SCF) extraction processes, including the latest research on the extraction of bioactive compounds from microalgae biomass and their benefits on human health. In addition, the role of key operating parameters on the selectivity of various compounds is discussed. This study provides useful knowledge that can productively contribute to the future development of SCF-based extraction technologies on an industrial scale.
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  • 29
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    Elsevier
    In:  Trends in Genetics, 36 (6). pp. 395-402.
    Publication Date: 2021-01-08
    Description: Aging entails an irreversible deceleration of physiological processes, altered metabolic activities, and a decline of the integrity of tissues, organs, and organ systems. The accumulation of alterations in the genetic and epigenetic spaces has been proposed as an explanation for aging. They result, at least in part, from DNA replication and chromosome segregation errors due to cell division during development, growth, renewal, and repair. Such deleterious alterations, including epigenetic drift, irreversibly accumulate in a stepwise, ratchet-like manner and reduce cellular fitness, similar to the process known as Muller’s ratchet. Here, we revisit the Muller’s ratchet principle applied to the aging of somatic cell populations and discuss the implications for understanding the origins of senescence, frailty, and morbidity.
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  • 30
    Publication Date: 2021-01-08
    Description: Natural cycles in the seawater partial pressure of carbon dioxide (CO2) in the Gulf of Maine, which vary in surface waters from ~250 to 550 µatm seasonally, provide an opportunity to observe how the life cycle and phenology of the shelled pteropod Limacina retroversa responds to changing food, temperature and carbonate chemistry conditions. Distributional, hydrographic, and physiological sampling suggest that pteropod populations are located in the upper portion of the water column (0–150 m) with a maximum abundance above 50 m. Gene expression and shell condition measurements show that the population already experiences biomineralization stress in the winter months when measured aragonite saturation state was at a seasonal low (though slightly oversaturated), reinforcing the usefulness of this organism as a bio-indicator for pelagic ecosystem response to ocean acidification. There appear to be two reproductive events per year with one pulse timed to coincide with the spring bloom, the period with highest respiration rate, fluorescence, and pH, and a second more extended pulse in the late summer and fall when saturation states remain high and fluorescence begins to decline. During the fall there is transcriptomic evidence of lipid storage for overwintering, allowing the second generation to survive the period of low food and aragonite saturation state. Based on these observations we predict that in the future pteropods will likely be most vulnerable to changing CO2 regionally during the fall reproductive event when CO2 concentration already naturally rises and when there is the added stress of generating lipid stores.
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  • 31
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    Elsevier
    In:  Computers & Geosciences, 139 . Art.Nr. 104482.
    Publication Date: 2021-01-08
    Description: We use numerical simulations on petrographically characterized thin-section images to predict three-dimensional elastic compressibility of sandstones. We predict two key statistics of compressibility curves measured under uniaxial boundary conditions in a laboratory - i) minimum compressibility at 1500 psi or 10 MPa depletion stress, and ii) maximum compressibility. A new Digital Rock workflow was developed for predicting compressibility based on the simulation of stress field using a segmented two-dimensional thin-section image. We also propose linear and non-linear relationships of log base 10 (compressibility) with in-situ porosity that can be used for compressibility prediction in the absence of laboratory measurements or two-dimensional images. Based on the results of application of the proposed relationships on samples from different fields with laboratory measurements, we conclude that the best prediction for minimum compressibility is obtained using the Digital Rock workflow and the best prediction for maximum compressibility is obtained using the proposed non-linear relationship using in-situ porosity. The range of compressibility values given by the difference between maximum and minimum compressibility predicted using the proposed methods can be used in making better informed economic decisions in field development planning.
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  • 32
    Publication Date: 2021-01-08
    Description: Pteropods are holopelagic marine snails and slugs that are of particular interest to science due to their role in marine food webs, global carbon cycle and their potential sensitivity to ocean change. Due to their pelagic, often exclusively offshore occurrence, samples are difficult to obtain, resulting in a lack of knowledge about their physiology, ecology, anatomy, geographical ranges, phylogenetic relationships and reproductive biology. Despite a recent increase in interest surrounding pteropod taxonomy, many evolutionary uncertainties remain due to limited taxon sampling and inavailability of molecular vouchers, in particular for the lesser investigated groups Pseudothecosomata and Gymnosomata. The Northwest Pacific Ocean is one of the least investigated areas for pteropods and in the adjacent semi-enclosed Sea of Okhotsk basin, current knowledge is restricted to the epipelagic zone. We summarize results from plankton hauls (from up to 5900 m depth) conducted during the joint German/Russian SokhoBio and KuramBio II cruises to the Sea of Okhotsk and the Kuril-Kamchatka-Trench region. This study presents an integrative taxonomic overview of six pteropod species identified by detailed morphological methods, including serial semithin sectioning, µCT and SEM scanning supported by multimarker (COI, 28S, and H3) genetic barcoding. We found four species of Gymnosomata slugs (Clione limacina, Clione okhotensis, Notobranchaea grandis and Thliptodon sp.), three species of Euthecosomata snails (Limacina helicina and two genetically delimited Clio spp.) and one shelled pseudothecosome species that is probably new to science (Peracle n. sp.). Multilocus phylogenetic analyses support monophyly of major traditional groups such as Pteropoda, Thecosomata, Pseudothecosomata and Gymnosomata. Micro-CT scanning was applied for the first time on pteropod soft bodies, allowing direct comparison between detailed anatomical peculiarities and molecular barcodes of the respective species. Furthermore, taxonomic positions, geographical ranges and potential dispersal barriers are discussed, with implications for future biodiversity comparisons. This study serves as a solid foundation for monitoring pteropods in a changing ocean.
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  • 33
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    Elsevier
    In:  European Journal of Medicinal Chemistry, 187 . Art.Nr. 111909.
    Publication Date: 2021-01-08
    Description: Hybrid chemical compounds formed by conjugation of two or more bioactive molecules have shown wide variety of applications in biology, microelectronics as well as material sciences. In particular, the conjugates of steroid framework are known to have broad biological activity profile due to their ability to penetrate the biomembranes and bind to specific hormone receptors. Among the various conjugates of steroids, Steroid Amino Acid Conjugates (SAACs) are attractive because of the possibility of fine tuning of the amphiphilicity with position, orientation and nature of amino acids. The structural details, applications, mechanistic insights and their diverse pharmacological as well as other physicochemical properties of several SAACs are summarized in the present review. This review provides better insight for medicinal chemists to design and explore such novel conjugates which can be used as lead structures in the future drug discovery or as probes to understand the complex biological system.
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  • 34
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    Elsevier
    In:  In: Green Sustainable Process for Chemical and Environmental Engineering and Science. , ed. by Inamuddin, Elsevier, Amsterdam, pp. 17-39, 23 pp. ISBN 978-0-12-817386-2
    Publication Date: 2020-05-08
    Description: Microalgal oils are considered an important source of industrially valuable oleochemicals with significant applications ranging from the energy to pharmaceutical sectors. Industrial production of microalgal oil is emerging rapidly; however, the high cost associated with downstream processes may constrain this process. Oils are accumulated intracellularly in oleaginous microalgae in the form of lipid droplets, which in turn require cell wall disruption followed by extraction in order to recover them. Disruption of the microalgal cell is very challenging owing to its distinctive features like high water content, hard cell wall, presence of algaenan, and sporopollenin like biopolymers that in turn create hurdles in efficient extraction of lipids. Various conventional pretreatment methods have been explored to rupture the cellular integrity of microalgal cells to enhance lipid extraction, and each method has certain advantages and disadvantages. Supercritical fluid extraction is the oldest technique for the extraction of valuable compounds from microalgae and is considered an alternative to conventional solvent extraction methods. It has several advantageous features such as being free from organic solvents (and their disposal), environment-friendly, and operating at a mild range of temperature (40–80°C). CO2 is considered to be an ideal supercritical fluid due to its non-toxic, non-flammable, and lipophilic nature. In this chapter, use of supercritical carbon dioxide extraction of lipids from microalgae is discussed and compared with other available lipid extraction methods.
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  • 35
    Publication Date: 2021-01-08
    Description: Cell disruption is regarded as an indispensable pretreatment step before the extraction of microalgae with biomineralized cell walls. Here, two typical microalgae—diatom Chaetoceros gracilis (C. gracilis) and coccolithophore Pleurochrysis carterae (P. carterae)—covered by “hard” biomineralized cell walls were used as starting materials for lipid extraction using liquefied dimethyl ether (DME) without any pretreatment such as drying or cell disruption. The liquefied DME extraction experiments were performed at 25 °C and 0.59 MPa using a semi-continuous, flow-type system. The results of the yield, elemental composition, molecular weight distribution, fatty acid composition, and trace element composition indicated that the performance of liquefied DME extraction was similar to that of Bligh–Dyer extraction and better than that of hexane Soxhlet extraction, despite the latter two methods requiring pre-drying and cell disruption processes. It was also proven that the cell wall of microalgae would not affect lipid extraction of liquefied DME, thereby the liquefied DME extraction method is suitable for extracting lipids from microalgae with biomineralized cell walls. Besides, the lipids extracted by liquefied DME can be further used for biodiesel production.
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  • 36
    Publication Date: 2021-01-08
    Description: In recent years, metagenomic strategies have been widely used to isolate and identify new enzymes from uncultivable components of microbial communities. Among these enzymes, various lipases have been obtained from metagenomic libraries from different environments and characterized. Although many of these lipases have characteristics that could make them interesting for application in biocatalysis, relatively little work has been done to evaluate their potential to catalyze industrially important reactions. In the present article, we highlight the latest research on lipases obtained through metagenomic tools, focusing on studies of activity and stability and investigations of application in biocatalysis. We also discuss the challenges of metagenomic approaches for the bioprospecting of new lipases.
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  • 37
    Publication Date: 2021-01-08
    Description: There are no effective therapies for achondroplasia. An open-label study suggested that vosoritide administration might increase growth velocity in children with achondroplasia. This phase 3 trial was designed to further assess these preliminary findings. Methods This randomised, double-blind, phase 3, placebo-controlled, multicentre trial compared once-daily subcutaneous administration of vosoritide with placebo in children with achondroplasia. The trial was done in hospitals at 24 sites in seven countries (Australia, Germany, Japan, Spain, Turkey, the USA, and the UK). Eligible patients had a clinical diagnosis of achondroplasia, were ambulatory, had participated for 6 months in a baseline growth study and were aged 5 to less than 18 years at enrolment. Randomisation was done by means of a voice or web-response system, stratified according to sex and Tanner stage. Participants, investigators, and trial sponsor were masked to group assignment. Participants received either vosoritide 15·0 μg/kg or placebo, as allocated, for the duration of the 52-week treatment period administered by daily subcutaneous injections in their homes by trained caregivers. The primary endpoint was change from baseline in mean annualised growth velocity at 52 weeks in treated patients as compared with controls. All randomly assigned patients were included in the efficacy analyses (n=121). All patients who received one dose of vosoritide or placebo (n=121) were included in the safety analyses. The trial is complete and is registered, with EudraCT, number, 2015-003836-11. Findings All participants were recruited from Dec 12, 2016, to Nov 7, 2018, with 60 assigned to receive vosoritide and 61 to receive placebo. Of 124 patients screened for eligibility, 121 patients were randomly assigned, and 119 patients completed the 52-week trial. The adjusted mean difference in annualised growth velocity between patients in the vosoritide group and placebo group was 1·57 cm/year in favour of vosoritide (95% CI [1·22–1·93]; two-sided p〈0·0001). A total of 119 patients had at least one adverse event; vosoritide group, 59 (98%), and placebo group, 60 (98%). None of the serious adverse events were considered to be treatment related and no deaths occurred. Interpretation Vosoritide is an effective treatment to increase growth in children with achondroplasia. It is not known whether final adult height will be increased, or what the harms of long-term therapy might be.
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  • 38
    Publication Date: 2021-01-08
    Description: Biofouling is a challenge in global sea-based salmon farming. Norway's salmon-growing industry relies primarily on copper-based antifouling coatings. However, copper is an increasingly recognised environmental hazard, and there is a need to develop alternative antifouling products to prevent biofouling in marine aquaculture. Using field experiments, this study compared the efficacy of six novel antifouling coatings for fish farm nets (two with reduced copper content, three with alternative biocides and one biocide-free coating) against a popular commercial copper coating and uncoated samples. The performance of one of the new coatings with lower copper content was more similar to the commercial copper control while the rest were colonised by biofouling faster and/or at higher abundances. However, none of the tested products were able to prevent biofouling entirely, underlining the importance of the search for alternative and improved antifouling technologies.
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  • 39
    Publication Date: 2021-01-08
    Description: Seagrass meadows are important productive ecosystems; during the Summer period in touristic beaches, such as those located in the high Adriatic coast, seagrasses are removed from the shoreline and disposed in landfill. This study investigated anaerobic digestion potential of beach-cast seagrass wrack, considering the physicochemical characteristics of the substrate and analysing heavy metal presence in the digestate, with the aim of transporting the material to local wastewater treatment plants to increase biogas yield from excess sludge anaerobic digestion. The methane production obtained from seagrass wrack was compared with three theoretical models. Seagrass wrack had a good methane potential of 103.1–262.3 NmL CH4/g Volatile Solids (VS), depending on substrate humidity and applied inoculum-to-substrate ratio. Predictive models, based on elemental composition and proximate analysis, successfully estimated methane yields; heavy metal concentration in digestate was low, boosting for digestate agricultural reuse. A simplified energy analysis revealed that transport to local wastewater treatment plants and use in anaerobic digestion process would provide up to 245,000 Nm3/y of methane, with an estimated economic income of 33,500–193,300 €/y, considering local seagrass production (1,465–8,454 t/y). Actual yearly costs sustained by beach management company for landfill disposal was about 117,200–676,320 €/y. Seagrass reuse in local digesters would compensate for the lack of excess sludge encountered during the cold season, allowing the digester to operate more continuously, increasing biogas production and reducing plant energy need.
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  • 40
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    Elsevier
    In:  In: Handbook of Algal Science, Technology and Medicine. , ed. by Konur, O. Elsevier, San Diego, pp. 675-696.
    Publication Date: 2020-04-08
    Description: The analysis of more than 400 papers found in the literature on Sargassum biosorption has shown the existence of more than 700 equilibrium entries corresponding to data at different temperature and pH conditions. The following ten single metals: Cd, Co, Cr(III, VI), Cu, Fe, Hg, La, Ni, Pb, and Zn, are the main focus of most of the equilibrium data (507) in more than half of the studied references. The studies reflecting the interaction of nine of these metals with Sargassum sp. is described and analyzed. The use of Langmuir equation, the effect of temperature and pH on sorption is critically reviewed. In addition, we also analyze all the data available on elemental chemical composition of native Sargassum. These data reflect the interaction of this kind of marine biomass with nine of the metals mentioned above, which are present in seawater worldwide.
    Type: Book chapter , NonPeerReviewed
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  • 41
    Publication Date: 2021-01-08
    Description: Six new compounds including two azaphilones, lunatoic acids D–E (1, 2), three isocoumarins, lunatinins B–D (3-5), and one α-pyrone derivative, lunatinin E (6), as well as four known ones, lunatoic acid A (7), lunatinin (8), penicipyran D (9) and chaetoquadrin F (10) were isolated from the rice medium of the gut fungus Paraphaeosphaeria sp. XZD2-1. Their planar structures were elucidated by analysis of 1D and 2D NMR as well as HRESIMS spectroscopic data. The absolute configurations of compounds 1-3 were assigned by experimental and calculated ECD data and an ester hydrolysis reaction. Compounds 4 and 5 were a pair of enantiomeric excess mixture. Structure of compound 6 was further confirmed by comparing optical rotation with known compounds according to literature. The antimicrobial activity and cytotoxicity of compounds 1-10 were examined.
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  • 42
    Publication Date: 2021-01-08
    Description: As the frequency and intensity of storms increase, a growing need exists for resilient shore protection techniques that have both environmental and economic benefits. In addition to producing seafood, aquaculture farms may also provide coastal protection benefits either alone or with other nature-based structures. In this paper, a generalized three-layer frequency dependent theoretical model is derived for random wave attenuation due to presence of biomass within the water column. The biomass can be characterized as submerged, emerged, suspended and floating canopies that can consist of natural aquatic vegetation with potential aquaculture systems of kelp or mussels. The present analytical solutions can reduce to the solutions by Mendez and Losada (2004), Chen and Zhao (2012) and Jacobsen et al. (2019) for submerged rigid aquatic vegetation. The present theoretical model incorporates the motion of these canopies using a cantilever-beam model for slender components and a buoy-on-rope model for elements with concentrated mass and buoyancy. Analytical results are compared with existing laboratory and field datasets for submerged and suspended canopies. The theoretical model was then used (in a case study at a field site in Northeastern US) to investigate the capacity of suspended mussel farms with submerged aquatic vegetation (SAV) to dissipate wave energy during a recent storm event. Compared to a dense SAV meadow in shallower water, the suspended aquaculture farms more effectively attenuate random waves with a smaller peak period and the higher frequency components of wave spectrum. The performance of suspended aquaculture farms is less affected by water level changes due to tides, surge and sea level rise, while the wave attenuation performance of SAV decreases with increasing water level due to decreased wave motion near the sea bed. Incorporating suspended aquaculture farms offshore significantly enhance the coastal protection effectiveness of SAV-based living shorelines and extend the wave attenuation capacity over a wider wave period and water level range. The combination of suspended aquaculture farms and traditional living shorelines provides a more effective nature-based coastal defense strategy than the traditional living shorelines alone.
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  • 43
    Publication Date: 2021-01-08
    Description: Application of polyester-degrading enzymes should be considered as an eco-friendly alternative to chemical recycling due to the huge plastic waste disposal nowadays. Many hydrolases from several fungi and bacteria have been discovered and successfully evaluated for their activity towards different aliphatic polyesters (PHA, PBS, PBSA, PCL, PLA), aromatic polyesters (PET, PBT, PMT) as well as their co-polyesters (PBST, PBAT, PBSTIL). This revision gives an up-to-date overview on the main biochemical features and biotechnological applications of those reported enzymes which are able to degrade polyester-based plastics, including different microbial polyester depolymerases, esterases, cutinase-like enzymes and lipases. Summarized information includes available protein sequences with the corresponding accession numbers deposited in NCBI server, 3D resolved structures, and data about optimal conditions for enzymatic activity and stability of many of these microbial enzymes that would be helpful for researchers in this topic. Although screening and identification of new native polyester hydrolases from microbial sources is undeniable according to literature, we briefly highlight the importance of the design of improved enzymes towards recalcitrant aromatic polyesters through different approaches that include site-directed mutagenesis and surface protein engineering.
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  • 44
    Publication Date: 2021-01-08
    Description: The subpopulation of Atlantic cod, Gadus morhua, in the eastern part of the Baltic Sea has experienced a significant increase in infections with anisakid nematode larvae of the species Contracaecum osculatum sensu lato (s.l.) since the year 2000. The life cycle of the parasite includes seals and especially the grey seal, Halichoerus grypus, as final hosts, carrying the adult nematodes in the stomach, crustaceans (copepods, amphipods) as first intermediate hosts and various fish species (clupeids, sandeel) including cod as second intermediate/paratenic hosts. Cod with a body length below 28 cm are generally non-infected but experience increasing infection levels when they switch to a piscine diet (infected intermediate/paratenic hosts). We present an overall frequency distribution analysis of worms in 166 cod (body length 30–49 cm) collected in the spawning area over the last 5 years. It shows a fit to the negative binomial distribution, a prevalence of infection of 89.8%, a mean intensity of 29.3 parasites per fish (range 1–377) and a variance/mean ratio of 59.2 (≫1), indicating overdispersion. We present measurements of the adult Contracaecum osculatum (s.l.) specimens in the seal stomach and show that the parasites reach a maximum length of 6.6 cm (females) and 5.8 cm (males). L3s in sprat have a total length from 1to 11 mm whereas the larvae in cod liver are 3–27 mm. A decreasing mean worm length associated with high worm densities in cod (number of nematodes per liver) was recorded. Possible explanations might include timing of feeding on infected intermediate/paratenic hosts, intraspecific competition (crowding) between larvae in cod and host responses (indicated by a significant antibody production in cod against C. osculatum (s.l.) antigens). A significant negative correlation between infection intensity and muscle mass of cod was found, suggesting parasite-induced down-regulation of growth factors in cod.
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  • 45
    Publication Date: 2021-01-08
    Description: Despite their critical role as the main energy pathway between phytoplankton and fish, the functional complexity of zooplankton is typically poorly resolved in marine ecosystem models. Trait-based approaches—where zooplankton are represented with functional traits such as body size—could help improve the resolution of zooplankton in marine ecosystem models and their role in trophic transfer and carbon sequestration. Here, we present the Zooplankton Model of Size Spectra version 2 (ZooMSSv2), a functional size-spectrum model that resolves nine major zooplankton functional groups (heterotrophic flagellates, heterotrophic ciliates, larvaceans, omnivorous copepods, carnivorous copepods, chaetognaths, euphausiids, salps and jellyfish). Each group is represented by the functional traits of body size, size-based feeding characteristics and carbon content. The model is run globally at 5° resolution to steady-state using long-term average temperature and chlorophyll a for each grid-cell. Zooplankton community composition emerges based on the relative fitness of the different groups. Emergent steady-state patterns of global zooplankton abundance, biomass and growth rates agree well with empirical data, and the model is robust to changes in the boundary conditions of the zooplankton. We use the model to consider the role of the zooplankton groups in supporting higher trophic levels, by exploring the sensitivity of steady-state fish biomass to the removal of individual zooplankton groups across the global ocean. Our model shows zooplankton play a key role in supporting fish biomass in the global ocean. For example, the removal of euphausiids or omnivorous copepods caused fish biomass to decrease by up to 80%. By contrast, the removal of carnivorous copepods caused fish biomass to increase by up to 75%. Our results suggest that including zooplankton complexity in ecosystem models could be key to better understanding the distribution of fish biomass and trophic efficiency across the global ocean.
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  • 46
    Publication Date: 2021-01-08
    Description: Mitigating human contributions to climate change is a highly debated topic, as it becomes evident that many nations do not adhere to optional reductions in global emission. Substantial research is taking place into negative carbon technologies that actively reduce the amount of atmospheric carbon dioxide (CO2) via greenhouse gas removal (GGR). Various GGR methods have been proposed, from reforestation to ocean fertilisation. This article discusses advantages of an approach based on enhanced input of tephra to the ocean, to increase the drawdown of atmospheric CO2. Natural addition of tephra to the ocean results in preservation of enhanced organic matter in sediment. Hence, augmenting its delivery should raise the level of sequestration. Calculations indicate that offshore tephra addition could sequester 2750 tonnes of CO2 per 50,000 tonnes of ash delivered (a typical bulk carrier’s capacity). The cost is estimated as ∼$55 per tonne of CO2 sequestered and is an order of magnitude cheaper than many proposed GGR technologies. Further advantages include: tephra addition is simply an augmentation of a natural Earth process, it is a low technology approach that requires few developments, and it may sequester carbon for thousands of years. Hence, offshore tephra addition warrants further investigation to assess its viability.
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  • 47
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    Elsevier
    In:  Progress in Oceanography, 189 . Art.-Nr.: 102452.
    Publication Date: 2021-02-08
    Description: Subsurface-intensified anticyclones are ubiquitous in the ocean, yet their impact on the large-scale transport of heat, salt and chemical tracers is poorly understood. These submesoscale coherent vortices (SCVs) can trap and advect waters thousands of kilometers away from the formation region, providing a transport pathway that is unresolved by low-resolution Earth System Models. However, knowledge of the importance of these eddies for the large scale circulation is hindered by the lack of systematic observations. Here, we take advantage of the global network of Argo floats to identify occurrences of these eddies, which appear as weakly stratified anomalous water masses with Gaussian-shaped vertical structures. We develop a general algorithm to detect subsurface eddies that have propagated away from their source region, and apply it to the database of Argo float profiles, resulting in roughly 4000 detections from more than 20 years of observations. We further group detections into regional populations to identify hot-spots of generation and mechanisms of formation. Analysis of regional SCV statistics reveals important sites of SCV generation in Eastern Boundary Upwelling Systems, marginal sea overflows, and mode water formation regions along major open-ocean fronts. Because of the heat and salt anomaly contained within their cores, SCV could leave a significant imprint on the hydrographic properties of water masses in regions of high SCV density.
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  • 48
    Publication Date: 2021-01-08
    Description: Used during an oil spill to minimise the formation of an oil slick, dispersants have negative biological effects on marine model organisms. However, no study has investigated the impacts of dispersants on adult sponge individuals. Here, we examine the effects of water accommodated oil fraction (WAF - oil in seawater), chemically enhanced WAF (CEWAF - oil and dispersant in seawater) and Benzo[A]Pyrene on sponge Halichondria panicea at physiological and molecular levels. Sponge clearance rate decreased sharply when exposed to WAF and CEWAF but the oil loading at which the clearance rate was reduced by 50% (ED50) was 39-fold lower in CEWAF than in WAF. Transcriptomic analysis revealed a homogenous molecular response with the greatest number of differentially expressed genes identified in CEWAF samples (1,461 genes). Specifically, genes involved in stress responses were up-regulated. This study presents evidence that the use of dispersants should be considered carefully in areas where sponges are present.
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  • 49
    Publication Date: 2021-01-08
    Description: This study evaluated the application of a Halobacteriovorax isolated from water of the Adriatic Sea (Italy) in controlling V. parahaemolyticus in mussels (Mytilus galloprovincialis). Two 72 h laboratory-scale V. parahaemolyticus decontamination experiments of mussels were performed. The test microcosm of experiment 1 was prepared using predator/prey free mussels experimentally contaminated with Halobacteriovorax/V. parahaemolyticus at a ratio of 103 PFU/105 CFU per ml, while that of experiment 2 using mussels naturally harbouring Halobacteriovorax that were experimentally contaminated with 105 CFU per ml of V. parahaemolyticus. For experiment 1, was also tested a control microcosm only contaminated with 105 CFU per ml of V. parahaemolyticus.. Double layer agar plating and pour plate techniques were used to enumerate Halobacteriovorax and V. parahaemolyticus, respectively. 16 S rRNA analysis was used to identify Halobacteriovorax. For both experiments in the test microcosm the concentration of prey remained at the same level as that experimentally added, i.e. 5 log for the entire analysis period. In experiment 1, V. parahaemolyticus counts in mussels were significantly lower in the test microcosm than the control with the maximum difference of 2.2 log at 24 h. Results demonstrate that Halobacteriovorax can modulate V. parahaemolyticus level in the mussels. The public impact of V. parahaemolyticus in bivalves is relevant and current decontamination processes are not always effective. Halobacteriovorax is a suitable candidate in the development of a biological approach to the purification of V. parahaemolyticus in mussels.
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  • 50
    Publication Date: 2021-01-08
    Description: The ctenophore Mnemiopsis leidyi, ranking among the 100 most damaging bioinvaders in the world, is a major predator of zooplankton, known to alter the biodiversity and functioning of the ecosystems in which it has been introduced. This first survey on the trophic relationships of M. leidyi in a Mediterranean lagoon (Berre, South of France) was performed through stable isotope analyses. Carbon and nitrogen isotope composition was used (1) to determine the types of prey ingested by this ctenophore and (2) the influence of individual size on its isotope composition, and (3) to make assumptions to explore its trophic relationships with the native jellyfish Aurelia sp.. The two gelatinous species ingested mainly (79% to 97% of the diet) planktonic prey (copepods, cirriped nauplii, gastropod larvae and cladocerans), but also preyed upon benthic organisms (mainly harpacticoid copepods and the amphipod Monocorophium insidiosum) in lower proportions (2.5% to 21%). Size-related changes in M. leidyi diet were evidenced with an increase in trophic level and benthic prey consumption in the larger individuals. These two gelatinous organisms probably play an important and underestimated role in the benthic–pelagic​ coupling in coastal lagoons by transferring benthic organic matter to the pelagic food webs.
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  • 51
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    Elsevier
    In:  Amsterdam, 432 pp., Elsevier, vol. 167, no. XVI:, pp. 385-389, (ISBN 1-56670-263-3)
    Publication Date: 1994
    Keywords: 93.1060 ; Crustal deformation (cf. Earthquake precursor: deformation or strain) ; Textbook of geophysics ; Plate tectonics ; Fracture ; Tectonics ; Geol. aspects ; Rheology ; Stress ; cracks and fractures (.NE. fracturing) ; salt
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  • 52
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    Elsevier
    In:  Amsterdam, Elsevier, vol. 31, no. 1, pp. 1-40, (ISBN 0-691-01019-6)
    Publication Date: 1994
    Keywords: Textbook of geophysics ; Geoelectrics ; Applied geophysics
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  • 53
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    Elsevier
    In:  Journal of Experimental Marine Biology and Ecology, 177 (1). pp. 73-78.
    Publication Date: 2020-07-27
    Description: The periodicity of deposition of growth increments in the cuttlebone of juvenile Sepia officinalis was investigated under controlled conditions for a short period after hatching (19 days). The slope of time elapsed and increment counts was significantly different from 1 indicating that lamellae are not deposited on a daily basis. The relationship between increment counts and juvenile length was, however, highly significant. Also significant were the relationships between the number of growth increments and shell length and increment counts and cuttlebone area. These data show that the number of growth increments is related primarily to the growth rate of the juvenile rather than to its chronological age. Taking into account these data, the cuttlebone lamellae cannot be used for age determination in the juvenile cuttlefish just after hatching.
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  • 54
    Publication Date: 2018-06-15
    Description: The levels of four trace metals (Cd, Cu, Pb, and Zn) in the whole soft body and in different organs of the ocean quahog Arctica islandica were evaluated from four stations in Kiel Bay, Western Baltic. The relationships between the contents and concentrations of these metals and body size (weight and length) were also investigated. Double logarithmic plots of metal contents and concentrations against dry body weight and shell length, respectively, show straight-line relationships. The results indicate that smaller individuals have higher concentrations of Cu and Zn, two essential metals, while larger individuals have higher concentrations of Cd and Pb, two non-essential metals. The calculated regression slopes of metal content against dry-body weight revealed that Cd and Cu appear to be affected by maturation since two different slopes are observed for both metals before and after maturation. This was not obvious for Pb and Zn. Pooled slopes of metal content against dry-body weight for all animal sizes indicated that Cu and Zn have a one common slope of (0.82) and Cd and Pb another common one of (1.51). Plots of metal concentrations against shell length indicated also that Cu and Zn have one common slope of (−0.54) and Cd and Pb another one of (1.56). Moreover, it was possible to calculate one final slope of (1.53) for Cd and Pb from both content/weight and concentration/length plots. This indicates that A. islandica may have one metabolic strategy for the essential metals and another for the non-essential metals.
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  • 55
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    Elsevier
    In:  Aquaculture, 128 (1-2). pp. 143-152.
    Publication Date: 2017-05-11
    Description: A simple method of providing a regular supply of live food for the experimental culture of paralarval cephalopods is described. The primary food source utilized was hatched zoeae of large laboratory populations of the hermit crab, Pagurus prideaux. Zoeal size, swimming behaviour, and distribution in the water column make these zoeae a suitable live prey for rearing early post-hatching planktonic stages of cephalopods and probably other marine zooplanktivores. Ovigerous P. prideaux females were collected from the sea throughout the year at depths between 10 and 90 m in the NW Mediterranean and maintained at densities of up to 500 specimens · m−2. One month after spawning in aquaria, 38% of the females of P. prideaux started to incubate a second clutch of eggs. Other decapod crustacean species, such as Liocarcinus depurator and Dardanus arrosor, were maintained to use their zoeae as a food source for cephalopod paralarvae. P. prideaux zoeae were used as the sole or main food resource for rearing Loligo vulgaris and Octopus vulgaris, during the first 2 months of life. First feeding and initial growth in L. vulgaris and O. vulgaris paralarvae can be successfully stimulated using decapod zoeae with a total length equivalent to 50–100% of the cephalopod's mantle length.
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  • 56
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    Elsevier
    In:  Marine Pollution Bulletin, 28 (7). pp. 413-416.
    Publication Date: 2018-04-09
    Description: As long as salinity in the Baltic Sea was high (as it was between 1948 and 1982) the depth range between 70 and 100 m suffered frequent anoxia. However, when salinity was low and when the position of the halocline was deep (as it was in the first half of the century) oxygen conditions were good and long-lived macrofauna occurred. Should the present trend to lower salinities continue (building bridges across the Belt Sea and reducing salt water inflow would be helpful) one can foresee a recolonization by macrofauna in the depth range 70–100 m.
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  • 57
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    Elsevier
    In:  Journal of Experimental Marine Biology and Ecology, 183 (1). pp. 41-52.
    Publication Date: 2019-09-23
    Description: The reproductive cycle of the sponge Halichondria panicea was investigated at Boknis Eck in the Western Kiel Bight over 2 yr, and over 1 yr on the island Helgoland in the North Sea and was compared with material collected earlier at Tjärnö at the Swedish west coast. Temperature and salinity were monitored at the different stations in order to determine whether different hydrographic conditions could be linked to differences in seasonal patterns of the reproductive cycle. The results showed H. panicea to be gonochoristic at all stations. The ratio of males to females varied between populations and years, but females predominated consistently. Comparison of the reproductive cycle in the years 1987 and 1989 at the brackish-water station Boknis Eck shows that high ambient winter and spring temperatures in 1989 resulted in a shorter period of oogenesis and earlier larval release, as compared to the year 1987. The reproductive cycle of the sponges at the fully marine station at Helgoland in 1989 and the brackish-water station at Tjärnö in 1978 under temperature and salinity conditions similar to those at Boknis Eck in 1989 showed the same seasonal pattern. We conclude that the lower salinities found at both Boknis Eck and Tjärnö do not cause a delay or slow-down of reproduction at these stations as compared to Helgoland. Under favourable temperature conditions, oogenesis was highly synchronous within the different populations, while it was more spread over time under the low ambient water temperatures at Boknis Eck in 1987.
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  • 58
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    Elsevier
    In:  Deep Sea Research Part I: Oceanographic Research Papers, 41 (2). pp. 263-281.
    Publication Date: 2018-06-19
    Description: In the Deep Western Boundary Current (DWBC) mean velocities obtained by the F11/F12 dating method are far smaller (1–2 cm s−1) than direct velocity measurements (5–20 cm s−1). To resolve this discrepancy, a simple box model is presented that uses the ideas of Pickartet al. (1989, Physical Oceanography, 19, 940–951) to parametrize turbulent diffusion of the current with its surroundings. In contrast to previous models, however, the boundary conditions include all water masses forming the lower part of the DWBC (Denmark Strait Overflow Water, Iceland Scotland Overflow Water and Northeast Atlantic Water). The model-derived mean velocity of the DWBC leads to tracer concentrations that have to fit the observed F11 and F12 distributions, the F11/F12 ratios, and the tritium distributions. Moreover, the model area is extended from south of the Faroe bank along the continental margin of the American continent to 10°S. The model assumes uniform velocity and uniform turbulent mixing along the flow path of the DWBC, and enhanced turbulent mixing in the vicinity of the current compared to the ocean's interior allows the surrounding waters, which remain motionless, to accumulate tracers. The highest mean velocity of the DWBC, which results in model F12, F11, and 3H distributions as well as F11/F12 ratios, compatible to measurements of these tracers along the western boundary, are 4.8 cm s−1. Variations in the composition of the DWBC as well as changes in the time history of the source water masses do not increase the range of the model velocities.
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  • 59
    Publication Date: 2017-08-23
    Description: Planktic foraminifers Neogloboquadrina pachyderma (sin.) from 87 eastern and central Arctic Ocean surface sediment samples were analyzed for stable oxygen and carbon isotope composition. Additional results from 52 stations were taken from the literature. The lateral distribution of δ18O (Full-size image (〈1 K)) values in the Arctic Ocean reveals a pattern of roughly parallel, W-E stretching zones in the Eurasian Basin, each ∼0.5‰ wide on the δ18O scale. The low horizontal and vertical temperature variability in the Arctic halocline waters (0–100 m) suggests only little influence of temperature on the oxygen isotope distribution of N. pachyderma (sin.). The zone of maximum δ18O values of up to 3.8‰ is situated in the southern Nansen Basin and relates to the tongue of saline (〉 33%.) Atlantic waters entering the Arctic Ocean through the Fram Strait. δ18O values decrease both to the Barents Shelf and to the North Pole, in accordance with the decreasing salinities of the halocline waters. In the Nansen Basin, a strong N-S δ18O gradient is in contrast with a relatively low salinity change and suggests contributions from different freshwater sources, i.e. salinity reduction from sea ice meltwater in the south and from light isotope waters (meteoric precipitation and river-runoff) in the northern part of the basin. North of the Gakkel Ridge, δ18O and salinity gradients are in good accordance and suggest less influence of sea ice melting processes. The δ13C (Full-size image (〈1 K)) values of N. pachyderma (sin.) from Arctic Ocean surface sediment samples are generally high (0.75–0.95‰). Lower values in the southern Eurasian Basin appear to be related to the intrusion of Atlantic waters. The high δ13C values are evidence for well ventilated surface waters. Because the perennial Arctic sea ice cover largely prevents atmosphere-ocean gas exchange, ventilation on the seasonally open shelves must be of major importance. Lack of δ13C gradients along the main routes of the ice drift from the Siberian shelves to the Fram Strait suggests that primary production (i.e. CO2 consumption) does probably not change the CO2 budget of the Arctic Ocean significantly.
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  • 60
    Publication Date: 2016-04-08
    Description: Two major meltwater events are documented in cores from the NW Labrador Sea. One occurred ca. 20,000 14C yr B.P. in association with deposition of a major detrital carbonate unit. Both prior to and after this event, δ18O values of near-surface planktonic foraminifera were 4.5%, indicating fully enriched glacial values. A younger event (ca. 14,000 14 C yr B.P.) is characterized by a dramatic change in δ18O from 4.5 to 2.0% and coincided with the retreat of ice from the outer SE Baffin Shelf, possibly into Hudson Strait. These meltwater events coincide with Heinrich (H) layers 1 and 2 from North Atlantic sediments. The 14,000 14C yr B.P. meltwater event indicates that the eastern margin of the Laurentide Ice Sheet also underwent rapid retreat at approximately the same time as other ice sheet margins around the NE North Atlantic. A third major detrital carbonate event at the base of HU87-033-009, possibly correlative with Heinrich layer 3, occurred ca. 33,960 ± 675 14 C yr B.P.; however, this is older than the accepted date for H-3 of 27,000 14C yr B.P. and may be H-4.
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  • 61
    Publication Date: 2019-09-24
    Description: For over thirty years man has studied “outer space” and installed satellites which watch the surface of the Earth. The great depths of the world ocean are, however, practically unknown and there is an urgent need to put abyssal benthic laboratories into “inner space” in order to study basic phenomena of interest to marine science and climatology as well as man's impact on the oceans. In view of the numerous problems related to global change, as a first step emphasis should first be on the role of the oceans and their inherent processes, which are the focus of such international programmes as the World Ocean Circulation Experiment (WOCE) and the Joint Global Ocean Flux Study (JGOFS). Multi-disciplinary registration of key events at selected key sites investigating the variability in time and space are of the utmost importance. The same methods and techniques must be used for the study of human impacts on the deep oceans caused by mining of metalliferous resources and by waste disposal as well as in basic studies. However, the investigation of the inner space of our planet has certain requirements. As long-term and large-scale investigations become more and more important, development of automized systems, largely independent from research vessels will be required. This will demand high capacities of energy for all technical functions as well as high storage capacities for data and samples. As a consequence the needs for two different—although overlapping—functional approaches are defined for future deep-sea deployments. (A) A system for long-term registration of the natural variability and long-term monitoring of human impacts: (B) A system for short-term observations and short-time experimentations. This report summarizes their technological demands. The envisioned interdisciplinary technology should deliver information on physical, biological and geochemical processes and their variabilities in the deep oceans. The prospected systems need to have the ability for real time video observation, data transfer and experimental manipulation, as well as sensing and sampling facilities with large storage capacities for long-term deployments. Prospective costs of the described multipurpose abyssal benthic laboratory will presumably exceed the funds for deep-sea research of a single country. A joint European effort could solve this problem and help to manifest a leading role for European marine science in international deep-sea and global change research.
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  • 62
    Publication Date: 2017-09-26
    Description: Three groups of REE patterns are observed for the sandstones and shales of the Middle Ordovician Austin Glen Member of the Normanskill Formation. One sandstone sample is enriched in middle and light rare earth elements. The majority of samples are light rare earth element (LREE) enriched with negative Eu-anomalies and flat heavy rare earth elements (HREEs), whereas a third group appears to have lost LREEs and middle rare earth element (MREEs). Homogeneous neodymium isotopic compositions for all samples at about the time of deposition, ϵNd (470 Ma) = −8.2 ± 1.1(2SD), indicate that the source of the Austin Glen Member was well mixed and that the neodymium had a long-term enriched history. The differences in the shape and abundances of the REE patterns combined with the neodymium isotope characteristics of the samples lead us to the conclusion that samarium and neodymium were fractionated and that the neodymium isotopic system might have been disturbed at about the time of deposition (470 Ma). Most samples appear to have been affected by this process. The two most altered shales lost about half of their neodymium and their ratios are higher than the ratios of average shales. These two shales give clearly erroneous mantle-extraction ages, but the average TDM of the provenance can still be deduced (1700–1800 Ma) from the least disturbed sandstones with normal upper crustal ratios. Accordingly, this study demonstrates that the REEs may be transported and neodymium isotopes may be reequilibrated under certain sedimentary conditions (e.g., diagenesis). However, in spite of evidence for REE redistribution, provenance information (TDM, original REE patterns) may still be inferred.
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  • 63
    Publication Date: 2019-09-23
    Description: The winter ice-regime of the 〈80 km wide Alaskan Beaufort Sea shelf is characterized by compression and shearing, resulting in the formation of major grounded pressure ridge systems stabilizing the fast ice on the mid-shelf, and essentially no open-water areas. In contrast, the winter ice-regime of the 500-km wide Laptev Sea shelf is controlled by winds blowing from land to sea, and is therefore dilational. A perennial polynya borders the hundreds of kilometers-wide and very smooth fast ice offshore. In this body of open water, rapidly forming ice is continuously advected offshore by the mean wind field, making the Laptev Sea the single major ice factory for the Arctic Ocean and Transpolar Drift. Conversely, with summer warming this dark polynya turns into an area of high heat gain, which results in the retreat of the ice edge to a much higher latitude and greater distance (〉500 km) from the mainland than in the Beaufort Sea. As a result, the annual freeze-up does not incorporate old, deep-draft ice, and with a lack of compression, such deep-draft ice is not generated in situ, as on the Beaufort Sea shelf. The Laptev Sea has as much as 1000 km of fetch at the end of summer, when freezing storms move in and large (6 m) waves can form. Also, for the first three winter months, the polynya lies inshore at a water depth of only 10 m. Turbulence and freezing are excellent conditions for sediment entrainment by frazil and anchor ice, when compared to conditions in the short-fetched Beaufort Sea. We expect entrainment to occur yearly. Different from the intensely ice-gouged Beaufort Sea shelf, hydraulic bedforms probably dominate in the Laptev Sea. Corresponding with the large volume of ice produced, more dense water is generated in the Laptev Sea, possibly accompanied by downslope sediment transport. Thermohaline convection at the midshelf polynya, together with the reduced rate of bottom disruption by ice keels, may enhance benthic productivity and permit establishment of open-shelf benthic communities which in the Beaufort Sea can thrive only in the protection of barrier islands. Indirect evidence for high benthic productivity is found in the presence of walrus, who also require year-round open water. By contrast, lack of a suitable environment restricts walrus from the Beaufort Sea, although over 700 km farther to the south. We could speculate on other consequences of the different ice regimes in the Beaufort and Laptev Seas, but these few examples serve to point out the dangers of exptrapolating from knowledge gained in the North American Arctic to other shallow Arctic shelf settings.
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  • 64
    Publication Date: 2018-01-17
    Description: Biometric analyses on shells of Turborotalita quinqueloba (Natland) reflect the paleoceanographic conditions in the Norwegian-Greenland Sea (NGS). Both median and mean size variations exhibit a steady increase after the Last Glacial Maximum (LGM). After Termination I the size eventually reaches a constant level with only minor fluctuation. In contrast, peak abundances of specimens occur somewhat later, during the Holocene climatic optimum and rapidly decrease again in the youngest sediments. Test sizes are larger at the Vøring Plateau in the vicinity of incoming Atlantic water than in water further to the west. Turborotalita quinqueloba first appeared in the southwestern part of the NGS with a preliminary major peak in abundance and size well below the Younger Dryas. This species was present in sizes 〈 125 μm in this area during almost entire oxygen isotopic Stage 2. This was not observed in the more easterly located cores. It seems likely that size variations as a ‘tool’ for NGS paleoceanographic interpretations are not only valuable for the time since the LGM, but can also be applied to older isotopic stages where abundances of T. quinqueloba are low or absent in the 〉 125 μm size-fractions but are high in the 63–125 μm fraction (e.g. Stages 7, 9 and 11).
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  • 65
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    Elsevier
    In:  Review of Palaeobotany and Palynology, 80 (3-4). pp. 209-234.
    Publication Date: 2016-09-14
    Description: Among living green algae assigned to the order Chlorococcales and order Zygnematales certain species develop resistant outer organic walls and/or cysts during their life cycles: as such they have the potential to become fossils. Based on morphology,comparison between living algae and microfossil remains are made with varying degrees of confidence, and a possible evolutionary pathway for certain chlorococcalean coenobial families is suggested. Twelve genera are reviewed from earliest to latest Triassic palynological assemblages from northwestern Australia; and the following taxa are described as new: Plaesiodictyon mosellanum ssp. symmetricum ssp. nov.; Plaesiodictyon mosellanurn ssp. variabile ssp. nov.; Plaesiodictvon decussatus sp. nov.: Plaesiodico'on decussatus ssp. decussatus ssp. nov.; Plaesiodictyon decussatus ssp. tetracornuta ssp. nov.; Tetraporina protrusa sp. nov.: Crucigeniella? torques sp. nov.; and Paleoraphidia akestra gen. et sp. nov. (type). Their suggested natural affinities are useful in palaeoenvironmental interpretations of mostly freshwater or low-salinity habitats.
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  • 66
    Publication Date: 2017-05-30
    Description: A method is presented to determine the extent of iron complexation by natural organic ligands in seawater. Catalytic cathodic stripping voltammetry (CSV) is used to take advantage of ligand competition between the added ligand, 1-nitroso-2-napthol (NN), and natural ligands present in seawater. The conditional stability constant for the complexation of iron by NN was calibrated for salinities between 1 and 36 using ligand competition with EDTA. The values of log K'(Fe(NN))3 (valid for pH 6.9 seawater) were found to vary linearly with log salinity according to log K'(Fe(NN))3 = - 1.04 +/- 0.08 log(salinity) + 30.12 +/- 0.09. The detection window, defined by the iron complexing ability of NN was altered by varying the concentration of NN. Preliminary measurements of iron complexing ligands in samples from coastal and open oceanic origin revealed the presence of natural complexing ligands at concentrations higher than that of total dissolved iron. The stability constants for the complexes were high, log K'(FeL) falling within the range of 18.8-21.2, indicating that by far the greatest component (99%) of the dissolved iron occurs organically complexed in pH 6.9 seawater. Model calculations showed that it is possible that the organic fraction may be somewhat less at a pH value near 8.
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  • 67
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    Elsevier
    In:  Earth and Planetary Science Letters, 125 (1-4). pp. 105-118.
    Publication Date: 2016-11-14
    Description: To investigate the growth rates and absolute time stratigraphy of marine hydrogenetic ferromanganese encrustations, we performed 10Be profiling and ‘Co chronometry’ of crustal layers, as well as 87Sr86Sr and δ18O analysis of phosphatised limestone (francolite) within a ∼ 9.5 cm thick ferromanganese crust from Schumann Seamount in the Hawaiian Archipelago. Together with microfossil stratigraphy, our results indicate that some seamount crusts greatly exceed the commonly accepted Miocene maximum age, in this case probably approaching the Cretaceous age of the seamount. In addition to the unconformity at the crust-substrate boundary, at least eight major disconformities are indicated in the Schumann Seamount crust which probably represent depositional hiatuses or episodes of crust erosion. Three of the six upper disconformities can be placed at the Plio-Pleistocene, Middle Miocene and Paleocene-Eocene based on 10Be, microfossil and Co chronometer evidence. 87Sr86Sr and δ18O values of purified francolite from an inclusion-rich layer between the depths of 44 and 49 mm suggest apparent ages that approach those of Eocene-Late Paleocene microfossils reported in overlying layers, whereas francolite vein infillings in the lower part of the crust and in the basaltic substrate yield values that, if interpreted as ages of phosphatization, suggest a minimum Oligocene age. Paleotracking suggests the phosphogenesis observed here and on other Central Pacific seamounts could not have resulted from upwelling enhanced productivity associated with equatorial divergence if the Oligocene and Middle Miocene isotopic ages reported here and elsewhere are correct; however, a maximum Late Paleocene age for the phosphogenesis, consistent with the stratigraphy, would place these seamounts within 10°N of the equator. Paleotracking also suggests northeast tradewind transport of aluminosilicates in the Cenozoic, in agreement with other evidence for the antiquity of this ferromanganese crust.
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  • 68
    Publication Date: 2017-12-06
    Description: We present comprehensive geochemical analyses on samples from the active volcanoes of the Society and Austral hotspot chains, including data for major, trace and rare-earth elements, and Sr, Nd, Pb and Th isotopes. The latter can be used to determine the Th/U in the source at the time of melting, and so give a constraint on the absolute amount of incompatible-element fractionation occurring during melting. SiO2 vs. MgO variations show evidence for variable amounts of a nephelinitic melt component (low SiO2, low MgO) in all the magmas studied. The nephelinite is probably produced in the presence of CO2 during melting. Correlations between SiO2 and the degree of ThU fractionation (derived from Th isotope measurements) imply that the CO2-driven, nephelinitic melting is also responsible for fractionating the Th/U ratio. Comparing the Th isotopes with Sr, Nd and Pb isotopes, it is possible to place limits on the Th/U ratios in the EM II (Societies) and HIMU (Australs) sources. These are ∼ 3.4 and ⩽ 2.5, respectively. The Nb/U ratio, which was previously thought to be relatively constant in all oceanic volcanics (47 ± 10), is shown to be anomalously low (25 ± 5) in some of the Society Seamounts and high (60) in some of the Australs. This confirms the presence of continent-derived material in the Society source and suggests that HIMU volcanics may have elevated Nb/U ratios. The change in Pb isotope compositions in the Australs, from HIMU (e.g., Tubuai) before 6 Ma to the more recent, less extreme compositions seen for example at Macdonald, is the result of a small amount of subducted sediment contaminating the pure old recycled oceanic crust component which, before 6 Ma, yielded HIMU.
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  • 69
    Publication Date: 2016-09-20
    Description: About 73% of the water exchange between the Baltic and the North Seas is via the Darss Sill. Joint Danish and German marine geological investigations, including shallow seismic surveys and sediment sampling, have been carried out in the Darss Sill area between 1989 and 1991. Results from these studies and unpublished archive data from the Institute of Baltic Sea Research, Warnemünde, are presented. These show that the entire Quaternary sedimentary sequence in most of the area is at least 40 m thick. A zone of glacial till outcropping between Denmark and Germany belongs to the Late Weichselian ice marginal line G (“Velgaster Staffel”). The formation of this line caused the damming of a pre-existing (sub)glacial meltwater discharge system. At the beginning of the Baltic Ice Lake formation, a deep and presently buried channel incised in this ice marginal line was part of a (glacio)fluvial drainage system with discharge towards the northeast, i.e. into the Baltic Ice Lake. During the Baltic Ice Lake transgression damming of the Darss Sill occurred due to accumulation of sandy sediments within this channel. On the other hand, the recent Kadet Channel was only occasionally overflown during the Baltic Ice Lake highstand maximum, which was 18 m BSL (below present sea level) in the Darss Sill area. The main erosion and deepening of the Kadet Channel began during the Ancylus Lake highstand maximum. At present, sediment transport on the Darss Sill is governed by northeasterly inflow of saline bottom waters in the entire area from the Kadet Channel to the German coast. Baltic outflow affects the seabed at shallower depth in the Danish sector. Large-scale current-induced bedforms in the area include, amongst others, sandwaves with a height of 5 m. Changes of the bedforms observed indicate a maximum bottom flow speed of 70–100 cm s−1, both for inflow and for outflow.
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  • 70
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    Elsevier
    In:  Deep-Sea Research Part II-Topical Studies in Oceanography, 41 . pp. 307-324.
    Publication Date: 2016-10-10
    Description: Measurements of the chlorofluorocarbons (CFCs), F11 (CCl3F) and F12 (CCl2F2) were made during the Shelf Edge Exchange Processes II (SEEP-II) experiment in the Middle Atlantic Bight during 1988–1989. These compounds undergo large seasonal variations in surface water concentration as a result of temperature-induced solubility changes. Outgassing in summer produces vertical concentration gradients that can be exploited to estimate a cross-pycnocline vertical eddy-diffusivity suitable for biogeochemical flux calculations. Model results based on an exploratory study suggest an average Kz of 1 × 10−5 m2 s−1 for this region during the stratified period. CFCs have advantages over other budget approaches for studying mixing processes, including heat budgets, as there are no internal sources or sinks other than air-sea gas exchange. In order to exploit further the CFC budget of sub-pycnocline shelf waters, regular cruises through the summer months and characterization of CFC levels at the time of stratification are required.
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  • 71
    Publication Date: 2016-10-10
    Description: The Shelf Edge Exchange Processes II (SEEP-II) program was designed to examine the potential for export of organic carbon from the continental shelf to the deeper ocean. In the Middle Atlantic Bight of the east coast, U.S.A., a “cold pool” of relict winter water is isolated by the development of a strong seasonal thermocline on the shelf. Oxygen concentrations were monitored in and above the cold pool from March 1988 to May 1989, with electrodes moored at 19 and 38 m at a 42-m station off the Delmarva Peninsula, eastern U.S.A. An oxygen-flux simulation model was constructed to describe long-term changes in oxygen concentration and saturation. The model utilized biological rate and biomass measurements obtained at the mooring location during cruises. Vertical eddy diffusion was constrained by comparison with the redistribution of chlorofluorocarbons and heat after stratification, and by sensitivity analyses. Model predictions of the average daily change in oxygen concentration and saturation at 38 m were in good agreement with average changes recorded by moored oxygen sensors, when biological generation of oxygen was approximately equal to the thermotrophic consumption. Strong, but transient, fluctuations concentration and saturation were clearly associated with specific advective events, and had little lasting impact on the overall long-term trends. Consequently, model parameters derived from intermittent, cruise-based observations yielded satisfactory predictions of long-term trends. A carbon budget was constructed for the stratified summer period from data that largely overlapped with those used for the oxygen model. The continental shelf ecosystem operates in approximate balance during the summer, with a potential export of no more than 4% of primary production.
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  • 72
    Publication Date: 2019-09-23
    Description: Despite the Arctic sea ice cover's recognized sensitivity to environmental change, the role of sediment inclusions in lowering ice albedo and affecting ice ablation is poorly understood. Sea ice sediment inclusions were studied in the central Arctic Ocean during the Arctic 91 expedition and in the Laptev Sea (East Siberian Arctic Region Expedition 1992). Results from these investigations are here combined with previous studies performed in major areas of ice ablation and the southern central Arctic Ocean. This study documents the regional distribution and composition of particle-laden ice, investigates and evaluates processes by which sediment is incorporated into the ice cover, and identifies transport paths and probable depositional centers for the released sediment. In April 1992, sea ice in the Laptev Sea was relatively clean. The sediment occasionally observed was distributed diffusely over the entire ice column, forming turbid ice. Observations indicate that frazil and anchor ice formation occurring in a large coastal polynya provide a main mechanism for sediment entrainment. In the central Arctic Ocean sediments are concentrated in layers within or at the surface of ice floes due to melting and refreezing processes. The surface sediment accumulation in central Arctic multi-year sea ice exceeds by far the amounts observed in first-year ice from the Laptev Sea in April 1992. Sea ice sediments are generally fine grained, although coarse sediments and stones up to 5 cm in diameter are observed. Component analysis indicates that quartz and clay minerals are the main terrigenous sediment particles. The biogenous components, namely shells of pelecypods and benthic foraminiferal tests, point to a shallow, benthic, marine source area. Apparently, sediment inclusions were resuspended from shelf areas before and incorporated into the sea ice by suspension freezing. Clay mineralogy of ice-rafted sediments provides information on potential source areas. A smectite maximum in sea ice sediment samples repeatedly occurred between 81°N and 83°N along the Arctic 91 transect, indicating a rather stable and narrow smectite rich ice drift stream of the Transpolar Drift. The smectite concentrations are comparable to those found in both Laptev Sea shelf sediments and anchor ice sediments, pointing to this sea as a potential source area for sea ice sediments. In the central Arctic Ocean sea ice clay mineralogy is significantly different from deep-sea clay mineral distribution patterns. The contribution of sea ice sediments to the deep sea is apparently diluted by sedimentary material provided by other transport mechanisms.
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  • 73
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    Elsevier
    In:  Journal of Marine Systems, 5 (6). pp. 411-423.
    Publication Date: 2017-06-26
    Description: Vertical flux of particulate material was recorded with moored sediment traps during 1988/1989 in the Greenland Sea at 72 degrees N, 10 degrees W. This region exhibits pronounced seasonal variability in ice cover. Annual fluxes at 500 m water depth were 22.79, 8.55, 2.39, 3.81 and 0.51 g m(-2) for total flux (dry weight), carbonate, particulate biogenic silicate, particulate organic carbon and nitrogen, respectively. Fluxes increased in April, maximum rates of all compounds occurred in May-June, and consistently high total flux rates of around 100 mg m(-2)d(-1) prevailed during the summer. The increasing flux of biogenic particles measured in April is indicative of an early onset of algal growth in spring. Small pennate diatoms dominated in the trap collections during April, and were still numerous during the high flux period when Thalassiosira species were the most abundant diatoms. During May-June, up to 22% of the Thalassiosira cells collected were viable-looking cells. The faecal pellet flux increased after the May-June event. Therefore we conclude that the diatoms settled as phytodetritus, most likely in rapidly sinking aggregates. From seasonal nutrient profiles it is concluded that diatoms contribute 25% to new production during spring and 50% on an annual basis. More than 50% of newly produced silicate particles are dissolved above the 500 m horizon. High new production during spring does not lead to a pronounced sedimentation pulse of organic matter during spring but elavated vertical export is observed during the entire growth period
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  • 74
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    Elsevier
    In:  Deep Sea Research Part I: Oceanographic Research Papers, 41 (7). pp. 1053-1068.
    Publication Date: 2018-01-17
    Description: The mean residence time of river-runoff on the shelves and in the halocline of the Arctic Ocean is estimated from salinity and tracer data (tritium, 3He and the 18O/16O ratio). These estimates are derived from comparison of apparent tracer ages of the halocline waters using a combination of tracers that yield different information: (1) the tritium “vintage” age, which records the time that has passed since the river-runoff entered the shelf; and (2) the tritium/3He age, which reflects the time since the shelf waters left the shelf. The difference between the ages determined by these two methods is about 3–6 years. Correction for the initial tritium/3He age of the shelf waters (about 0.5–1.5 years) yields a mean residence time of the river-runoff on the shelves of the Siberian Seas of about 3.5 ± 2 years.
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  • 75
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    Elsevier
    In:  Marine Geology, 121 (1-2). pp. 121-128.
    Publication Date: 2016-06-23
    Description: Two cores recovered in the Greenland Sea contain aggregates (up to 5 cm in diameter) of poorly sorted coarse-grained material. Their lithologic and biogenic content, in addition to the grain size and grain shape, indicate that they are related to till balls. It is possible that they formed in a fluvial or nearshore environment (perhaps in Greenland or Siberia), were frozen into fast ice, and were then transported by sea ice-rafting to their present location. Since the balls were still partly frozen, they could survive the 2000 m drop through the water column to the seafloor.
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  • 76
    Publication Date: 2019-05-14
    Description: A combined high resolution seismic, sub-bottom profiling, and multi-beam echo-sounding survey in the Skagerrak (Danish sector of the North Sea) together with gas analyses at a station along the profile exhibit the expulsion of gas (mainly methane) and the presence of gas-charged sediments at shallow depth. The echo-soundings yield detailed insight into the distribution and shape of typical sea-floor features associated with gas seepage, such as pockmarks. The pockmarks reach dimensions of 800 m in length, 300 m in width, and 15 m in depth, with the long axis running parallel to the slope of the Norwegian Trench. Processing of the multi-channel high resolution seismic data and the digitally recorded sub-bottom profiler signals indicate an internal compressional velocity of about 1050 m s-1 within the gas-charged sediments reaching from the sea-floor to a sub-bottom depth of about 23 m. Using the lateral distribution and thickness of the gas-charged sediments in conjunction with a mean concentration of gas of 3000 ppb, the present amount of trapped gas is estimated to be 6·45 × 1011 g CH4. The flux of methane through the sea-bed into the water column appears to be 7·2 × 1010 g CH4 per year. To explain the small difference in size between the methane pool in near-surface sediments and the annual flux through the sea-bed, a constantly high supply of methane from leaking hydrocarbon reservoirs at greater depths has to be active.
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  • 77
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    Elsevier
    In:  Analytica Chimica Acta, 284 (3). pp. 463-471.
    Publication Date: 2020-06-03
    Description: An automated and semi-intelligent voltammetric system is described for trace metal analysis. The system consists of a voltammeter interfaced with a personal computer, a sample changer, 2 peristaltic pumps, a motor burette and a hanging mercury drop electrode. The system carries out fully automatically approximately 5 metal determinations per hour (including at least 3 repetitive scans and calibration by standard addition) at trace levels encountered in clean sea water. The computer program decides what level of standard addition to use and evaluates the data prior to switching to the next sample. Alternatively, the system can be used to carry out complexing ligand titrations with copper whilst recording the labile copper concentration; in this mode up to 8 full titrations are carried out per day. Depth profiles for chromium speciation in the Mediterranean Sea and a profile for copper complexing ligand concentrations in the North Atlantic Ocean measured on board-ship with the system are presented. The chromium speciation was determined using a new method to differentiate between Cr(III) and Cr(VI) utilizing adsorption of Cr(III) on silica particles.
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  • 78
    Publication Date: 2020-06-03
    Description: The use of in-line UV-digestion for breakdown of dissolved organic matter (DOM), prior to voltammetric determination of trace metals in natural samples, is discussed in this paper. Destruction of DOM is necessary to free trace metals that are organically complexed and to remove interfering organic surfactants. Complete breakdown of DOM in natural water samples is achieved by in-line UV-digestion using a 100 W medium pressure mercury vapour lamp and a silica coil, at a sample digestion time of 4.5 min. The efficiency of the system is tested with destruction of humic acid, conversion of Cr(III) to Cr(VI), and the release of Ni and Cu from organic complexes in sea water. The in-line application of UV is illustrated by automated voltammetry of nanomolar levels of Cu and Ni in samples from oceanic origin.
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  • 79
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    Elsevier
    In:  TrAC - Trends in Analytical Chemistry, 13 (9). pp. 348-352.
    Publication Date: 2020-05-04
    Description: Instrumentation and methods are described for collecting surface sea water using pumping with subsequent in-line analysis by stripping voltammetry or chronopotentiometry. The review is illustrated with data for estuarine copper and nickel, and the distribution of nickel in Liverpool Bay.
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  • 80
    Publication Date: 2019-06-11
    Description: Geochemical and Sr, Pb, O and C isotopic data are reported for carbonatite samples from five locations in southeast Brazil. Elemental abundances and δ13CPDB data (between −5.8 and −7.2‰) prove that all the samples are derived from the mantle. Dupal isotopic characteristics in the all carbonatite samples from five locations in southeast Brazil are found in this study, characteristics that have not previously been recognized in carbonatites. Brazilian carbonatites possess average values of between 101 and 145, average values of between 5.2 and 10.3, and initial Sr isotopic compositions of between 0.7046 and 0.7062. The Brazilian carbonatites comprise two groups: The northern group is coincident with the passage of the Trindade non-Dupal hotspot at ca. 80 Ma, while the southern group mainly corresponds to the passage of the Tristan de Cunha Dupal hotspot at ca. 130 Ma. Although we expected a geochemical correlation between the Brazilian carbonatites and the South Atlantic hotspots, the enriched isotopic signature (EM1) of all the carbonatite samples is similar to that of alkali basalts on Tristan de Cunha. The combined OSr isotopic diagram indicates that the southern group carbonatites have negligible or only slight crustal contamination. The northern group samples show significantly higher δ18OSMOW values of 9–14‰, more radiogenic Pb isotopic ratios, and a value of 0.705. Even if these signatures are derived from the contamination of a lower crustal component with mantle sources, it is clear that the parental magma also has inherent EM1 isotopic characteristics. The interpretation of the origin of EM1 in the Brazilian carbonatites (subcontinental lithospheric mantle vs. asthenosphere) is dependent on the model of Paraná volcanism at ca. 130 Ma, which remains controversial. One possibility is that both the northern and southern carbonatites came from enriched SCLM under a part of Gondwanaland. In this case, a hotspot would provide the thermal energy to melt the lithospheric source region for both the Paraná flood basalts and the alkali carbonatitic volcanism. Another possibility is that the source of the northern carbonatites is also the Tristan plume carbonate-rich material which had once been trapped under the crust and reactivated by the Trindade hotspot, on the assumption that Paraná volcanism at ca. 130 Ma was mainly triggered by the huge Tristan plume activity. If anything, we favour the latter and believe an asthenospheric mantle plume origin for both the ultimate carbonate source and the Dupal anomaly in the Brazilian carbonatites.
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  • 81
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    Elsevier
    In:  Fisheries Research, 21 . pp. 1-15.
    Publication Date: 2021-01-19
    Description: The aims of this project were to improve understanding of the basic life.cycle biology, stock structure, trophic interactions and fisheries exploitation of northeast Atlantic squid, in particular the loliginids Loligo forbesi and Loligo vulgaris. Multivariate analysis of morphometric data and isozyme electrophoresis shows that L. forbesi populations from the coast of mainland Europe are fairly homogeneous, but that those from the Azores are a distinct stock. Loligo forbesi and L. vulgaris are annual species with a peak of breeding in the winter (December-May) throughout the geographical range, and one or more seasonal peaks of recruitment. Loligo are probably batch spawners. Males grow larger than females, mature about 1 month earlier and recruit earlier to the fishery. Sexual maturity occured at two distinct size classes, more obviously in males than females. Fish, including many cimmercially important species, and Crustacea, were the dominant prey of Loligo. The incidence of fish in the diet increases with squid size. Squid of all types are eaten by fish, seals, cetaceans and seabird, although quantitative estimates of consumption by these trophic levels were low. Catches of squid from northeast Atlantic waters increased over the period 1980-1990 but currently supply only a minor component of the European market for squid, the balance being made up by imports. The squid catch in the northern part of the range shows wide fluctuations in abundance by area and by season. The applicability of assessment methods for these stocks is limited by inadequate and inaccurate statistical information, and because nearly all of the catch arises by-catch from finfisheries.
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  • 82
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    Elsevier
    In:  Netherlands Journal of Sea Research, 33 (1). pp. 57-63.
    Publication Date: 2018-08-14
    Description: Studies on dormant resting cysts of the dinoflagellates Scrippsiella lachrymosa Lewis 1991 and S. trifida Lewis 1991 from Recent North Sea sediments suggest that their motile forms, which have not yet been officially recorded in this area till now, are common members of the North Sea plankton community. Cyst surveys offer avenues to overcome problems in spatial and temporal distributions and in taxonomy, and will help the compilation of a phytoplankton inventory in an area.
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  • 83
    Publication Date: 2019-09-23
    Description: The present paper reviews the literature related to the life cycle of the prymnesiophyte Phaeocystis and its controlling factors and proposes novel hypotheses based on unpublished observations in culture and in the field. We chiefly refer to P. globosa Scherffel as most of the observations concern this species. P. globosa exhibits a complex alternation between several types of free-living cells (non-motile, flagellates, microzoopores and possibly macrozoospores) and colonies for which neither forms nor pathways have been completely identified and described. The different types of Phaeocystis cells were reappraised on the basis of existing microscopic descriptions complemented by unpublished flow cytometric investigations. This analysis revealed the existence of at least three different types of free-living cells identified on the basis of a combination of size, motility and ploidy characteristics: non-motile cells, flagellates and microzoospores. Their respective function within Phaeocystis life cycle, and in particular their involvement in colony formation is not completely understood. Observational evidence shows that Phaeocystis colonies are initiated at the early stage of their bloom each by one free-living cell. The mechanisms controlling this cellular transformation are still uncertain due to the lack of information on the overwintering Phaeocystis fomms and on the cell type responsible for colony induction. The existence of haploid microzoospores released from senescent colonies gives however some support to sexuality involvement at some stages of colony formation. Once colonies are formed, at least two mechanisms were identified as responsible of the spreading of colony form: colony multiplication by colonial division or budding and induction of new colony from colonial cells released in the external medium after colony disruption. The latter mechanism was clearly identified, involving at least two successive cell differentiations in the following sequence: motility development, subsequent flagella loss and settlement to a surface, mucus secretion and colony formation, colonial cell division and colony growth. Aggregate formation, cell motility development and subsequent emigration from the colonies, release of non-motile cells after colony lysis on the other hand, were identified as characteristics for termination of Phaeocystis colony development. These pathways were shown to occur similarly in natural environments. In the early stages of the bloom however, many recently-formed colonies were found on the setae of Chaetoceros spp, suggesting this diatom could play a key-rôle in Phaeocystis bloom inception. Analysis of the possible environmental factors regulating the transition between the different phases of the life cycle, suggested that nutrient status and requirement of a substrate for attachment of free-living cells would be essential for initiation of the colonial form. Physical constraints obviously would be important in determining colony shape and fragmentation although autogenic factors cannot be excluded. Some evidence exists that nutrients regulate colony division, while temperature and nutrient stress would stimulate cell emigration from the colonies.
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  • 84
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    Elsevier
    In:  Continental Shelf Research, 14 (4). pp. 385-399.
    Publication Date: 2018-08-17
    Description: The Bass Strait cascade is a wintertime downwelling caused by cooling of the shallow waters of Bass Strait. During winter, a front separates the cold shelf water from the waters of the Tasman Sea. Continuous horizontal bands of downwelled water leading oceanward beneath the front imply that it can be transgressed near the bottom anywhere along its length. However, by far the greatest volume crosses at a breach at the northern end. Measured currents in eastern Bass Strait fit a predictable pattern: eastward toward the front, then as the front is approached, swinging north towards the breach. Flow northwards along the slope after downwelling is quantified using a simple analytic model. Cascade water found in the “far-field” was found only in small patches. One such patch was found to possess motion independent from the mean flow in which it was embedded.
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  • 85
    Publication Date: 2018-03-21
    Description: This chapter throws the attention on the meiobenthos of the deep northeast Atlantic. The main purpose of this chapter is to summarize new results from an area lying between 15°N and 53°N and extending from the continental margin of western Europe and northwest Africa to the Mid-Atlantic Ridge. It considers first the nature and scope of meiofaunal research in the northeast Atlantic and then discuss the environmental parameters, which are believed to influence meiofaunal organisms. This chapter then discusses the various types and scales of pattern observed among meiofaunal populations within the study area, progressing from the large-scale bathymetric and latitudinal trends and then to small-scale horizontal patterns within particular areas. Faunal densities and faunal composition are considered separately and compared with data from other regions. This chapter also deals with the distribution of meiofauna within sediment profiles and the temporal variability of populations. This chapter concludes by discussing the recent review of deep-sea meiofauna, which focused mainly on the abundance and biomass data from different oceans and on the relationship between the biomass of the meiofauna and that of other faunal components
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  • 86
    Publication Date: 2018-03-08
    Description: The 10Be records of four sediment cores forming a transect from the Norwegian Sea at 70°N (core 23059) via the Fram Strait (core 23235) to the Arctic Ocean at 86°N (cores 1533 and 1524) were measured at a high depth resolution. Although the material in all the cores was controlled by different sedimentological regimes, the 10Be records of these cores were superimposed by glacial/interglacial changes in the sedimentary environment. Core sections with high 10Be concentrations ( 〉 1 · 109 at/g) are related to interglacial stages and core sections with low10Be concentrations ( 〈 0.5 · 109 at/g) are related to glacial stages. Climatic transitions (e.g., Termination II, 5/6) are marked by drastic changes in the 10Be concentrations of up to one order of magnitude. The average 10Be concentrations for each climatic stage show an inverse relationship to their corresponding sedimentation rates, indicating that the 10Be records are the result of dilution with more or less terrigenous ice-rafted material. However, there are strong changes in the 10Be fluxes (e.g., Termination II) into the sediments which may also account for the observed oscillations. Most likely, both processes affected the 10Be records equally, amplifying the contrast between lower (glacials) and higher (interglacials) 10Be concentrations. The sharp contrast of high and low 10Be concentrations at climatic stage boundaries are an independent proxy for climatic and sedimentary change in the Nordic Seas and can be applied for stratigraphic dating (10Be stratigraphy) of sediment cores from the northern North Atlantic and the Arctic Ocean
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  • 87
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    Elsevier
    In:  Deep Sea Research Part I: Oceanographic Research Papers, 41 (4). pp. 721-739.
    Publication Date: 2017-07-21
    Description: In situ measurement of fluid flow rates from active margins is an important parameter in evaluating dissolved mass fluxes and global geochemical balances as well as tectonic dewatering during developments of accretionary prisms. We have constructed and deployed various devices that allow for the direct measurement of this parameter. An open bottom barrel with an exhaust port at the top and equipped with a mechanical flowmeter was initially used to measure flow rates in the Cascadia accretionary margin during an Alvin dive program in 1988. Sequentially activated water bottles inside the barrel sampled the increase of venting methane in the enclosed body of water. Subsequently, a thermistor flowmeter was developed to measure flow velocities from cold seeps. It can be used to measure velocities between 0.01 and 50 cm s−1, with a response time of 200 ms. It was deployed again by the submersible Alvin in visits to the Cascadia margin seeps (1990) and in conjunction with sequentially activated water bottles inside the barrel. We report the values for the flow rates based on the thermistor flowmeter and estimated from methane flux calculations. These results are then compared with the first measurement at Cascadia margin employing the mechanical flowmeter. The similarity between water flow and methane expulsion rates over more than one order of magnitude at these sites suggests that the mass fluxes obtained by our in situ devices may be reasonably realistic values for accretionary margins. These values also indicate an enormous variability in the rates of fluid expulsion within the same accretionary prism. Finally, during a cruise to the active margin off Peru, another version of the same instrument was deployed via a TV-controlled frame within an acoustic transponder net from a surface ship, the R.V. Sonne. The venting rates obtained with the thermistor flowmeter used in this configuration yielded a value of 4411 m−2 day−1 at an active seep on the Peru slope. The ability for deployment of deep-sea instruments capable of measuring fluid flow rates and dissolved mass fluxes from conventional research vessels will allow easier access to these seep sites and a more widespread collection of the data needed to evaluate geochemical processes resulting from venting at cold seeps on a global basis. Comparison of the in situ flow rates from steady-state compactive dewatering models differ by more than 4 orders of magnitude. This implies that only a small area of the margin is venting and that there must be recharge zones associated with venting at convergent margins
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  • 88
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    Elsevier
    In:  Marine Chemistry, 47 . pp. 115-125.
    Publication Date: 2018-03-02
    Description: A widely used degassing method for methane in seawater employing vacuum was tested and subsequently improved. It yielded 62 ± 3.8% of the total dissolved methane, hence a reproducible correction factor was established. The method was then applied to measure CH4 in the sea-air boundary layer and simultaneously in the overlying air along two transects in the eastern Equatorial Pacific off Peru in March of 1992. The results showed surprising small-scale reversals of the methane exchange between ocean and atmosphere in this region. Generally the ocean acted as a source of methane but also methane uptake by the ocean was found. This was mainly a consequence of high CH4 concentrations in the air which deviated considerably from the long-term and large-scale average. If applied to the flux rate calculations, the observed variabilities indicate that both rate and direction of the methane flux through the air-sea interface vary considerably depending on the atmospheric CH4 content. The implications are that even ocean areas with high concentrations of dissolved CH4 can be considerably weaker sources than would be expected on the basis of 1.7 ppmv mean atmospheric methane content. Based on improved simultaneous analyses of both air and water samples, the ocean-atmosphere flux of methane would therefore be more dynamic than previously thought.
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  • 89
    Publication Date: 2019-05-14
    Description: The Cenozoic sediments sampled in ODP Leg 104 on the Vøring Plateau show a distinct variability of the total organic carbon content (TOC) and the accumulation rates of TOC. Based on the geochemical and organic-petrographic characterization of the sedimentary organic matter (OM), the allochthonous and autochthonous proportion of the OM could be quantified.The results clearly demonstrate that high TOC percentages and TOC accumulation rates in Cenozoic sediment sections display a generally high input of allochthonous organic matter. Oxidized and partly well-rounded organic particles built up the main portion of OM within the Miocene, TOC-rich sediments. The most probable source of this oxidized OM are reworked sediments from the Scandinavian shelf. Changes in the input of these organic particles are to some degree correlative with sea-level changes.The Cenozoic accumulation of autochthonous OM is low and does not reveal a clear variation during the Miocene and early Pliocene. In spite of a high accumulation rate of biogenic opal during the Early Miocene, the accumulation rate of autochthonous TOC is low. The autochthonous particle assemblage is dominated by relatively inert OM, like dinoflagellate cysts. This points to an intensive biological and/or early diagenetic degradation of the marine OM under well oxidized bottom water conditions during the last 23 Myr. Nevertheless, a continuation of marine OM degradation during later stages of diagenesis cannot be excluded.A prominent dominance of allochthonous OM over autochthonous is documented with the beginning of the Pliocene. At 2.45 Ma the episodic occurrence of ice-rafted, thermally mature OM reflects the onset of the glacial erosion of Mesozoic, coal and black shale bearing sediments on the Scandinavian and Barents Sea shelves. The first occurrence of these, in view of the actual burial depth, thermally overmature OM particles is, therefore, a marker for the beginning of the strong Scandinavian glaciation and the advance of the glacial front toward the shelves.
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  • 90
    Publication Date: 2018-03-21
    Description: In order to assess recent submarine volcanic contributions to the sediments from the active Kolbeinsey Ridge, surface samples were analyzed chemically. The contribution of major and trace elements studied differ within the study area. A statistical analysis of the geochemical variables using factor analysis and cluster method allows to distinguish possible sample groups. Cluster method identifies three distinct sediment groups located in different areas of sedimentation. Group 1 is characterized by highest contents of Fe2O3, V, Co, Ni, Cu and Zn demonstrating the input of volcaniclastic material. Group 2 comprises high values of CaCO3, CaO and Sr representing biogenic carbonate. Group 3 is characterized by the elements K, Rb, Cs, La and Pb indicating the terrigenous component. The absolute percentage of the volcanic, biogenic and terrigenous components in the bulk sediments was calculated by using a normative sediment method. The highest volcanic component (〉 60% on a carbonate free basis) is found on the ridge crest. The biogenic component is highest (10–30%) in the eastern part of the Spar Fracture Zone influenced by the East Iceland Current. Samples from the western and southeastern region of the study area contain more than 90% of terrigenous component which appears to be mainly controlled by input of ice-rafted debris.
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  • 91
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    Elsevier
    In:  Amsterdam, Elsevier, vol. 65, no. ALEX(01)-FR-77-01, AFTAC Contract F08606-76-C-0025, pp. 95-104, (ISBN: 0-08-044051-7)
    Publication Date: 1993
    Keywords: Textbook of geophysics ; GeodesyY ; Geothermics ; Planetology ; ConvolutionE
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  • 92
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    Elsevier
    In:  Marine Pollution Bulletin, 26 (3). pp. 152-155.
    Publication Date: 2018-03-22
    Description: Skin and hair samples of harbour seals (Phoca vitulina) found dead along the west coast of northern Germany in 1988 were analysed for total mercury, cadmium and lead. Cadmium and lead concentrations were below the detection limit in most skin samples. The mercury content of the hair (median: 23.1 μg g−1 wet wt) was several magnitudes higher than the mercury content of the skin (0.27 μg g−1 wet wt). Mercury concentrations in hair samples were significantly higher than lead concentrations (0.54 μg g−1 wet wt), which significantly exceeded cadmium levels (0.09 μg g−1 wet wt). Female seals revealed lower cadmium concentrations in the hair than male seals. Accumulations of metals with age were observed for cadmium and lead in hair samples and for mercury in skin samples of male seals. A connection between metal accumulation and pigmentation or rather moult was clearly recognizable.
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  • 93
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    Elsevier
    In:  Deep Sea Research Part I: Oceanographic Research Papers, 40 (2). pp. 267-291.
    Publication Date: 2018-03-22
    Description: The spreading of Mediterranean Water (MW) released through the Straits of Gibraltar is studied with hydrographic data, oxygen, nutrients and for the first time with chlorofluoromethane (CFM, compounds F11 and F12) distributions along seven sections in the Gulf of Cadiz, and with measurements in the Western Alboran Sea and west of the Gulf. The properties of MW entering the Gulf are deduced from CFM-salinity correlations east and west of the Straits as well as from property-depth profiles in the Western Alboran Sea. At the time of the survey, the outflow originated from depths above the salinity maximum of the Intermediate Water in the Alboran Sea. It turned out that the F11/F12 ratio of the outflow is equal to the ratios found in the Atlantic water in the Gulf of Cadiz; thus the ratio carries no time information in the region. A model is developed to describe mixing of the MW undercurrent with overlying North Atlantic Central Water (NACW) from different depths. The contribution of each layer to the mixing is parameterized by a weighting factor, which has to satisfy the balances of potential temperature (θ), CFMs, oxygen and nutrients in the MW undercurrent. It is shown that entrainment of water from shallower depths into the undercurrent is important near the Iberian Continental Shelf. Farther west and south, the undercurrent mainly mixes with water from near the salinity minimum of the NACW. For regions where the undercurrent has left the bottom, additional mixing with North Atlantic Deep Water (NADW) has to be taken into account. The percentage of MW in the undercurrent decreases from 76% hear the Straits to about 34% at 7°30′W for the lower core (MI) and about 22–24% for the upper core (Mu). Assuming an outflow of undiluted MW through the Straits of 1.0 Sv, the transport of the undercurrent can be calculated by determining an average dilution factor for each section. The undercurrent transports 2.0 Sv just west of the Straits and 3.6 Sv leave the Gulf of Cadiz. At 36°N, 9°54′W, a meddy with unusually high temperatures and salinities below 500 m was found, covering the density range for both cores, Mu and Ml. From the θ−S characteristics and the evaluated mixing scheme of the meddy it appears to have formed near 7°W in the Gulf, a region up to now not proposed in the literature, and moved westward without much further mixing.
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  • 94
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    Elsevier
    In:  International Journal for Parasitology, 23 (6). pp. 749-755.
    Publication Date: 2018-03-23
    Description: In April 1990, 488 marine fish belonging to 30 species from central Phillipine waters were examined for flesh parasitic infections that may affect their consumability. One species of hemirhamphids and 3 species of belonids harboured plerocercoids of Otobothrium penetrans Linton, 1907 (Proceedings of the U.S. National Museum33, 85–126). This is the first record of this parasite from Pacific fish species. The highest intensity of infection found was 8 in Tylosurus crocodilus. Most of the larvae were located between the dorsal spines of the vertebral column, only 32% were found in the fillets. Based on the present material we give a description of the plerocercoid stage of the species using scanning electron microscopy of the armature and morphometrical measurements. Comparison to results from earlier findings of O. penetrons by Linton (1907; 1924, Proceedings of the U.S. National Museum64, 1–114) and to O. kurisi by Shields (1985, International Journal for Parasitology15: 635–643) lead to the conclusion that the latter species is a synonym for O. penetrans.
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  • 95
    Publication Date: 2018-03-21
    Description: Nine large box cores collected in the western Greenland-Iceland-Norwegian (GIN) Sea were analyzed for calcium carbonate content and coarse fraction components. Stratigraphic control is based on oxygen isotope records performed on four of the cores. All cores were correlated using oxygen and carbon isotope data, fluctuations in calcium carbonate content, coarse terrigenous particle content and volcanic ash beds. Glacial and interglacial cycles are documented by a number of terrigenous particle events and differentiated calcium carbonate production which can be correlated to major paleoceanographic and paleoclimatic shifts. In the older core sections, extensive deposition of ice-rafted detritus (IRD) persisted until about oxygen isotope stage 9 and document a relatively stable environment in this area, strongly influenced by cold surface water masses. The following interval was characterized by variations in the general surface water circulation pattern, although high amounts of IRD are still present in Iceland Sea sediments. Pronounced shifts in terrigenous input and pelagic carbonate records were identified close to the oxygen isotope stage Full-size image (〈1 K) and Full-size image (〈1 K) boundaries, indicating massive melting of icebergs in the western GIN Sea. These enormous inputs of debris were followed by an increase in calcium carbonate production caused by maximum intrusion of warm Atlantic surface waters. Relatively high calcium carbonate contents also show that only little dilution by fine-grained material and a minimum of ice melting occurred during these warm phases. During oxygen isotope stage 5, conditions were more uniform indicating a less pronounced westward penetration of Atlantic waters as compared to the Holocene. The last glacial (stages 4-2) is characterized by the occurrence of “Heinrich”-like events, although high IRD contents were present throughout this interval. A distinct contrast between the northernmost cores and the cores in the south is indicative of a rather strong westward penetration of Atlantic water in the north and of an area dominated by cold water east of the Kolbeinsey Ridge during the Holocene. However, conditions west of Jan Mayen seem to have remained constantly dominated by cold surface waters throughout the whole time investigated.
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  • 96
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    Elsevier
    In:  Deep Sea Research Part II: Topical Studies in Oceanography, 40 (3). pp. 783-800.
    Publication Date: 2018-03-05
    Description: Horizontal distribution of myctophid fishes were studied from two transects in the Arabian Sea in 1987. Species numbers exhibited a south-north decline in diversity, with only half of the fish taxa occupying the northeastern region. Diaphus arabicus was the dominant species both in the south and north. All recorded myctophid fish species migrate in a diel pattern, residing during daytime at depths of extremely low oxygen levels (〈0.1 ml O2 1−1) and foraging in the oxygen-rich surface layer at night. Feeding patterns were determined for the six most abundant myctophid species. All species appeared to be opportunistic predators that prey on a comparatively narrow food spectrum consisting principally of small to medium sized copepods. Numerically, non-calanoid copepods (with Oncaea conifera and O. venusta dominating) made up to 70% of the diet of D. arabicus and Bolinichthys longipes. Of the 26 calanoid copepod species identified from the six myctophid taxa, the genera Euchaeta, Pleuromamma and Candacia generally dominated in the stomachs, with P. indica constituting between 21 and 95% (by numbers) of the calanoid copepod prey.
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  • 97
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    Elsevier
    In:  Deep Sea Research Part I: Oceanographic Research Papers, 40 (6). pp. 1155-1168.
    Publication Date: 2018-03-05
    Description: Particulate fluxes of aluminium, cadmium, cobalt, copper, iron, manganese, nickel, phosphorus, lead, vanadium and zinc in the northeast subtropical Atlantic Ocean have been determined from sediment trap samples collected between 1 December 1986 and 30 April 1987 at 1020 and 4120 m below the ocean surface. The fluxes of most elements (except Cd and P) show small variations between the different layers, and are closely associated with the vertical transport of aluminium. Elemental composition and flux rates suggest that aerosol loadings from northeast trade winds are the major contributor of these elements to depositing material. Extremely low fluxes of copper, lead and zinc also indicate that anthropogenic perturbations are of insignificant importance in this region.
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  • 98
    Publication Date: 2018-03-05
    Description: Within the framework of the JGOFS Pilot Study in 1989 mesozooplankton (0.2–20 mm) was sampled by means of a Hydro-Bios multinet in five depth strata (0–25, 25–50, 50–100, 100–200, 200–500 m) during four Lagrangian drift experiments of 8–14 days' duration at 18, 33, 46 and 58°N, to follow the seasonal progress of the phytoplankton spring bloom development in the northeast Atlantic. Mesozooplankton standing stock, measured as dry weight and ash-free dry weight, increased by a factor of about 6 from 18 to 58°N. Day/night differences amounted to 10–20% of the average and were—with one exception at 18°N—not statistically significant. Using the data on weight-specific respiration rates measured by colleagues on the same cruise, the ingestion rates and potential community grazing of mesozooplankton on phytoplankton within the upper 100 m of the water column were calculated. During all four drift experiments, quasi-steady-state conditions were observed in phyto- and zooplankton standing stock, primary production and daily sedimentation at 100 m depth. The maximum potential grazing rate by mesozooplankton accounted for about half of the daily primary production. Since sedimentation of fresh phytoplankton was negligible, it is concluded that the grazing pressure exercised by mesozooplankton together with micro- and nanozooplankton was responsible for keeping the phytoplankton standing stock at a more or less constant level during the investigated spring bloom in the four areas. Particle flux was thus dominated by zooplankton faecal material.
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  • 99
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    Elsevier
    In:  Journal of Chromatography A, 642 (1-2). pp. 425-434.
    Publication Date: 2019-02-27
    Description: Accurate congener-specific determination of chlorobiphenyl congeners (all 209 congeners) is finally possible with the use of multidimensional gas chromatography-electron-capture detection techniques. The effectiveness of this technique for environmental analyses is enhanced by ultraclean laboratory practices, non-destructive extraction and clean-up steps and the use of low-volume, high-efficiency HPLC separation for various classes of organic contaminants. In the light of these new developments conventional procedures for chlorobiphenyl analysis are evaluated.
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  • 100
    facet.materialart.
    Unknown
    Elsevier
    In:  Deep Sea Research Part II: Topical Studies in Oceanography, 40 (3). pp. 711-735.
    Publication Date: 2018-03-05
    Description: The productivity regime and size structure of phytoplankton are described for three different epipelagic systems in the Arabian Sea during the inter-monsoon period in spring 1987: (1) the coast of Oman; (2) the central Arabian Sea; and (3) the shelf off Pakistan. These results are related to the functioning of the specific ecosystem. Off the coast of Oman, the transition from a surface maximum of autotrophic biomass and production to a more oligotrophic system, with a chlorophyll subsurface maximum, was observed. Concomitantly, the size spectrum changed towards a higher significance of picoplankton. In the central Arabian Sea, a typical oligotrophic system with a pronounced subsurface maximum of autotrophic biomass and primary production was encountered. Here, the epipelagic system could be divided into two distinct sub-systems: the surface layer “regenerated” production, the predominance of picophytoplankton and minor losses due to sedimentation, thus a “closed” system; and the subsurface maximum layer at the nutricline characterized by higher sedimentation losses and more diatoms. Both sub-systems showed about the same productivity, the turnover in the surface layer having been much greater than in the subsurface maximum. The system on the shelf off Pakistan is seen as a decay stage of the open ocean system when water from offshore is transported onto the shelf during the onset of monsoon winds.
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