| 1. |
- Lee, Sang-Han, et al.
(författare)
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Distribution of plutonium and americium in the marginal seas of the nothwest pacific ocean.
- 2003
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Ingår i: Deep-sea research. Part II, Topical studies in oceanography. - 0967-0645 .- 1879-0100. ; 50, s. 2727-2750
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Tidskriftsartikel (refereegranskat)abstract
- Plutonium isotopes and 241Am were studied in seawater and sediment from the East China Sea, the Yellow Sea, the East Sea/Sea of Japan, the Sea of Okhotsk, and the northwest Pacific Ocean, collected between 1993 and 1996 with the aim to contribute to better understanding the behaviour of plutonium and americium in the marine environment. 239,240Pu concentrations in surface water varied from 2.3 to 13 µBq l-1 in the East China Sea and from 3.5 to 9.4 µBq l-1 in the East Sea. The 239,240Pu vertical profiles in water showed a broad subsurface maximum between 500 and 1000 m with a range of 30-40 µBq l-1, and gradually decreased from 1000 m depth down to the seafloor. 241Am concentrations in surface water showed values from 1.1 to 2.2 µBq l -1 in the East Sea, from 1.0 to 3.1 µBq l-1 in the Sea of Okhotsk, and from 0.68 to 12.0 µBq l-1 in the northwest Pacific Ocean. The activity ratios of 241Am/239,240Pu in seawater showed values similar to the global fallout ratio, which suggests that the source of these radionuclides in the northwest Pacific Ocean is global fallout. However, the 241Am/239,240Pu activity ratios in sediment were found to be much higher (1.0-1.9) than the global fallout ratio (0.37), confirming that 241Am is scavenged from the water column more rapidly than 239,240Pu. The 239,240Pu inventories in the water column of the East Sea were from 0.98 to 93 Bq m-2 depending on water depth and sedimentation rates. The 241Am inventory in the water column east of Kamchatka was 6.3 ± 1.0 Bq m -2 and the sediment inventory in the Sea of Okhotsk was 16 ± 2 Bq m-2. 239,240Pu concentrations in sinking particles in the southwest Japan Basin were from 3.7 to 5.2 Bq kg-1 (dry weight) with fluxes of 0.19-4.50 mBq m-2 d-1 and at the Ulleung Basin from 2.4 to 3.7 Bq kg-1 (dry weight) with fluxes of 0.77-1.10 mBq m-2 d-1. The mean residence time of 239,240Pu in the water column of the East Sea derived from sediment trap data was 140 ± 20 years, 2-3 times less than in the Atlantic and Pacific oceans.
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| 2. |
- Bacheler, N. M., et al.
(författare)
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Do walleye pollock exhibit flexibility in where or when they spawn based on variability in water temperature?
- 2012
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Ingår i: Deep-Sea Research Part Ii-Topical Studies in Oceanography. - : Elsevier BV. - 0967-0645 .- 1879-0100. ; 65-70, s. 208-216
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Tidskriftsartikel (refereegranskat)abstract
- Environmental variability is increasingly recognized as a primary determinant of year-class strength of marine fishes by directly or indirectly influencing egg and larval development, growth, and survival. Here we examined the role of annual water temperature variability in determining when and where walleye pollock (Theragra chalcogramma) spawn in the eastern Bering Sea. Walleye pollock spawning was examined using both long-term ichthyoplankton data (N=19 years), as well as with historical spatially explicit, foreign-reported, commercial catch data occurring during the primary walleye pollock spawning season (February-May) each year (N=22 years in total). We constructed variable-coefficient generalized additive models (GAMs) to relate the spatially explicit egg or adult catch-per-unit-effort (CPUE) to predictor variables including spawning stock biomass, season, position, and water temperature. The adjusted R-2 value was 63.1% for the egg CPUE model and 35.5% for the adult CPUE model. Both egg and adult GAMs suggest that spawning progresses seasonally from Bogoslof Island in February and March to Outer Domain waters between the Pribilof and Unimak Islands by May. Most importantly, walleye pollock egg and adult CPUE was predicted to generally increase throughout the study area as mean annual water temperature increased. These results suggest low interannual variability in the spatial and temporal dynamics of walleye pollock spawning regardless of changes in environmental conditions, at least at the spatial scale examined in this study and within the time frame of decades. Published by Elsevier Ltd.
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| 3. |
- Beldowski, Jacek, et al.
(författare)
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Chemical Munitions Search & Assessment-An evaluation of the dumped munitions problem in the Baltic Sea
- 2016
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Ingår i: Deep-sea research. Part II, Topical studies in oceanography. - : Elsevier BV. - 0967-0645 .- 1879-0100. ; 128, s. 85-95
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Tidskriftsartikel (refereegranskat)abstract
- Chemical Munitions Search & Assessment (CHEMSEA) project has performed studies on chemical weapon (CW) detection, sediment pollution and spreading as well as biological effects of chemical warfare agents (CWAs) dumped in the Baltic Sea. Results suggest that munitions containing CWAs are more scattered on the seafloor than suspected, and previously undocumented dumpsite was discovered in Gdansk Deep. Pollution of sediments with CWA degradation products was local and close to the detected objects; however the pollution range was larger than predicted with theoretical models. Bottom currents observed in the dumpsites were strong enough for sediment re-suspension, and contributed to the transport of polluted sediments. Diversity and density of the faunal communities were poor at the dumping sites in comparison to the reference area, although the direct effects of CWA on benthos organisms were difficult to determine due to hypoxic or even anoxic conditions near the bottom. Equally, the low oxygen might have affected the biological effects assessed in cod and caged blue mussels. Nonetheless, both species showed significantly elevated molecular and cellular level responses at contaminated sites compared to reference sites.
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| 4. |
- Bertilsson, Stefan, et al.
(författare)
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Influence of solar radiation on the availability of dissolved organic matter to bacteria in the Southern Ocean
- 2004
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Ingår i: Deep-Sea Research II: Topical Studies in Oceanography. - : Elsevier BV. ; 51, s. 2557-2568
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Tidskriftsartikel (refereegranskat)abstract
- The influence of solar radiation on the ability of dissolved organic matter (DOM) to support bacterial growth, was studied in the eastern Atlantic sector of the Southern Ocean during the SWEDARP 1997/1998 cruise with SA Agulhas December 1997–February 1998. Vertical profiles of water samples (2–3000 m) were obtained from the Spring Ice Edge (SIE, 60°S, high chlorophyll-a) and from the Winter Ice Edge (WIE, 56°S, low chlorophyll-a) areas. Filter-sterilized water from each area and depth was incubated under natural solar radiation and in the dark for comparison. Photobleaching of humic substance fluorescence occurred in all studied water samples. The bleaching was typically larger in the initially more fluorescent deep waters, compared to the low-fluorescent surface waters. Both the irradiated water and the dark controls were re-inoculated with a mixed bacterial inoculum from the initially sampled water. Bacterial growth (accumulating cells) and bacterial production (protein synthesis) were monitored during a 16–19 day incubation of these cultures at near in situ temperature (2 °C). Bacterial growth in cultures prepared from SIE water was largest at the surface (2–25 m), while the growth in corresponding cultures from the WIE did not vary much over depth. In contrast to the observed photobleaching, no clear effects of the irradiation on the ability of the DOM to support bacterial growth could be observed in either of the experiments. Hence, the degradation of fluorescent structures and other photochemical alterations of the organic matter did not have a major effect on the total pool of biodegradable organic substrates. The lack of effects of photoreactions on bacterial growth potential in the present study disagrees with the short-term bacterial growth response observed in other oceanic environments. This could be due to the different experimental approaches employed (short-vs. long-term incubations) or may indicate that the impact of photoreactions on bacterial growth in the Southern Ocean differ substantially from aquatic systems that are more influenced by terrestrial environments, as well as the warmer oligotrophic oceanic environments.
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| 5. |
- Burd, Adrian B., et al.
(författare)
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Assessing the Apparent Imbalance Between Geochemical and Biochemical Indicators of Meso- and Bathypelagic Biological Activity: What the @$#! is wrong with present calculations of carbon budgets?
- 2010
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Ingår i: Deep-sea research. Part II, Topical studies in oceanography. - : Elsevier BV. - 0967-0645 .- 1879-0100. ; 57:16, s. 1557-1571
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Tidskriftsartikel (refereegranskat)abstract
- Metabolic activity in the water column below the euphotic zone is ultimately fuelled by the vertical flux of organic material from the surface. Over time, the deep ocean is presumably at steady state, with sources and sinks balanced. But recently compiled global budgets and intensive local field studies suggest that estimates of metabolic activity in the dark ocean exceed the influx of organic substrates. This imbalance indicates either the existence of unaccounted sources of organic carbon or that metabolic activity in the dark ocean is being over-estimated. Budgets of organic carbon flux and metabolic activity in the dark ocean have uncertainties associated with environmental variability, measurement capabilities, conversion parameters, and processes that are not well sampled. We present these issues and quantify associated uncertainties where possible, using a Monte Carlo analysis of a published data set to determine the probability that the imbalance can be explained purely by uncertainties in measurements and conversion factors. A sensitivity analysis demonstrates that the bacterial growth efficiencies and assumed cell carbon contents have the greatest effects on the magnitude of the carbon imbalance. Two poorly quantified sources, lateral advection of particles and a population of slowly settling particles, are discussed as providing a means of closing regional carbon budgets. Finally, we make recommendations concerning future research directions to reduce important uncertainties and allow a better determination of the magnitude and causes of the unbalanced carbon budgets. (C) 2010 Elsevier Ltd. All rights reserved.
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| 6. |
- Engqvist, A, et al.
(författare)
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Archipelago strait exchange processes - an overview
- 2004
-
Ingår i: Deep-sea research. Part II, Topical studies in oceanography. - : Elsevier BV. - 0967-0645 .- 1879-0100. ; 51:4-5, s. 371-392
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Tidskriftsartikel (refereegranskat)abstract
- Archipelagos consist of a set of islands forming a collection of basins interconnected by straits, and are typically characterized by widely varying spatial and temporal scales regarding geometry and forcing conditions. Focusing on the strait exchange parameterization, we describe an archipelago water exchange model in which the archipelago is subdivided into a network of discrete basins and interconnecting straits and where the time integration assumes a series of quasi-steady states. We propose an algorithm that should be sufficiently flexible to provide reasonable strait exchange estimates under the variety of forcing conditions encountered in the Stockholm archipelago. We start from the functional formulation of two-layer hydraulic theory, which allows numerical schemes to be designed that, given the forcing conditions at the ends of a given strait, distinguish between maximal and sub-maximal flow cases and solve the flow accordingly. We relax the assumption of two homogeneous layers when necessary, using an approximate method based on a self-similarity assumption and with the sea-level difference over the strait as an explicit part of the problem. This method allows exchange flows with two groups of layers to be solved for the same set of geometries that the pure two-layer theory can handle, including sill-contraction combinations and non-rectangular cross-sections. We further show how aspiration of dense water from below the sill crest can be quantified with hydraulic theory, and be included in the method for stratified strait exchange. Rotational control in wide straits and in parallel straits connecting the same two basins is treated with a simple but robust scheme. We evaluate the calculations with data from the Oxdjupet strait in the Stockholm archipelago. Simulations with a three-dimensional, non-hydrostatic numerical model are performed to compensate for sparsity in data.
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| 7. |
- Gong, Xun, et al.
(författare)
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Of Atlantic Meridional Overturning Circulation in the CMIP6 Project
- 2022
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Ingår i: Deep-Sea Research Part II: Topical Studies in Oceanography. - : Elsevier BV. - 0967-0645 .- 1879-0100. ; 206
-
Tidskriftsartikel (refereegranskat)abstract
- The Atlantic Meridional Overturning Circulation (AMOC) upper-cell circulation is widely linked to global oceans and climate. Here, we focus on a statistical overview about the modelled AMOCs on the basis of the historical simulations in the 5th and 6th phase of the Coupled Model Intercomparison Project (CMIP5 and CMIP6), including the modelled AMOC strength, cell structure, long-term trend and the variabilities on interannual, decadal and multi-decadal scales. Our results show that the multi-model averaged AMOC mean state of CMIP5 is insignificantly different from the CMIP6 results, meanwhile the corresponding multi-model averaged AMOC variability is reduced from CMIP5 to CMIP6 results. Moreover, the CMIP6 multi-model averaged AMOC becomes further distinct from the mean state of Rapid Climate Change (RAPID) observations. Overall, 7 out of the 18 CMIP6 models have suggested AMOC strengthening, meanwhile 6 models have indicated declining trends in the AMOC, with the rest 5 models in the variabilities with insignificant trends. Overall, the CMIP6 results have suggested pronounced modelling discrepancies in revealing AMOC trends, distinct from the more commonly weakening trend of the AMOCs in the CMIP5 simulations. Moreover, the multi-model averaged AMOC variabilities are comparable between CMIP5 and CMIP6 simulations, on inter-annual, decadal and multi-decadal time scales, with the discrepancies remaining among models.
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| 8. |
- Graneli, W., et al.
(författare)
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Bacterial abundance, production and organic carbon limitation in the Southern Ocean (39-62°S, 4-14°E) during the austral summer 1997/1998
- 2004
-
Ingår i: Deep-sea research. Part II, Topical studies in oceanography. - : Elsevier BV. - 0967-0645 .- 1879-0100. ; 51, s. 2569-2582
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Tidskriftsartikel (refereegranskat)abstract
- Bacterial abundance and production were studied in different zones in the Southern Ocean (39-62°S, 4-14°E) during a cruise in December-January 1997/1998. The role of potential growth limitation of bacteria due to limited availability of organic carbon (glucose) or inorganic N and P was studied in parallel. A positive correlation between surface water temperatures (-2 to 18°C) and bacterial abundance (
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| 9. |
- Hennige, S. J., et al.
(författare)
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Short-term metabolic and growth responses of the cold-water coral Lophelia pertusa to ocean acidification
- 2014
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Ingår i: Deep-sea research. Part II, Topical studies in oceanography. - : Elsevier BV. - 0967-0645 .- 1879-0100. ; 99, s. 27-35
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Tidskriftsartikel (refereegranskat)abstract
- Cold-water corals are associated with high local biodiversity, but despite their importance as ecosystem engineers, little is known about how these organisms will respond to projected ocean acidification. Since preindustrial times, average ocean pH has decreased from 8.2 to similar to 8.1, and predicted CO2 emissions will decrease by up to another 0.3 pH units by the end of the century. This decrease in pH may have a wide range of impacts upon marine life, and in particular upon calcifiers such as cold-water corals. Lophelia pertusa is the most widespread cold-water coral (CWC) species, frequently found in the North Atlantic. Here, we present the first short-term (21 days) data on the effects of increased CO2 (750 ppm) upon the metabolism of freshly collected L pertusa from Mingulay Reef Complex, Scotland, for comparison with net calcification. Over 21 days, corals exposed to increased CO2 conditions had significantly lower respiration rates (11.4 +/- 1.39 SE, gmol O-2 g(-1) tissue dry weight h(-1)) than corals in control conditions (28.6 +/- 7.30 SE mu mol O-2 g(-1) tissue dry weight h(-1)). There was no corresponding change in calcification rates between treatments, measured using the alkalinity anomaly technique and C-14 uptake. The decrease in respiration rate and maintenance of calcification rate indicates an energetic imbalance, likely facilitated by utilisation of lipid reserves. These data from freshly collected L pertusa from the Mingulay Reef Complex will help define the impact of ocean acidification upon the growth, physiology and structural integrity of this key reef framework forming species.
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| 10. |
- Malinverno, Elisa, et al.
(författare)
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Silicoflagellates in the eastern mediterranean and Black Seas : Seasonality, distribution and sedimentary record
- 2019
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Ingår i: Deep-sea research. Part II, Topical studies in oceanography. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0967-0645 .- 1879-0100. ; 164, s. 122-134
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Tidskriftsartikel (refereegranskat)abstract
- Silicoflagellate populations and fluxes were analyzed from water samples and sediment traps in several basins of the eastern Mediterranean and Black Sea, to show species distribution in response to ecological factors and compared with the Quaternary records of the region. In the eastern Mediterranean, Dictyocha stapedia was the most abundant species, represented by two varieties: var. stapedia, smaller and with an apex spine, that dominated in the pelagic settings, and var. aspinosa, larger and lacking an apex spine, that dominated in the north Adriatic Sea. Dictyocha aculeata was the second most abundant species, Octactis pulchra was seasonally dominant in the Adriatic Sea. Stephanocha speculum occurred sporadically in the Adriatic Sea with 6-sided normal-sized specimens, but was nearly absent from pelagic assemblages. In the Black Sea, assemblages and fluxes were characterized by larger 7-sided skeletons of D. speculum with apex spines and a lower abundance of O. pulchra.
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| 11. |
- Nagata, Toshi, et al.
(författare)
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Emerging concepts on microbial processes in the bathypelagic ocean – ecology, biogeochemistry and genomics
- 2010
-
Ingår i: Deep-sea research. Part II, Topical studies in oceanography. - : Elsevier BV. - 0967-0645 .- 1879-0100. ; 57:16, s. 1519-1536
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Tidskriftsartikel (refereegranskat)abstract
- This paper synthesizes recent findings regarding microbial distributions and processes in the bathypelagic ocean (depth > 1000 m). Abundance, production and respiration of prokaryotes reflect supplies of particulate and dissolved organic matter to the bathypelagic zone. Better resolution of carbon fluxes mediated by deep microbes requires further testing on the validity of conversion factors. Archaea, especially marine Crenarchaeota Group I, are abundant in deep waters where they can fix dissolved inorganic carbon. Viruses appear to be important in the microbial loop in deep waters, displaying remarkably high virus to prokaryote abundance ratios in some oceanic regions. Sequencing of 18S rRNA genes revealed a tremendous diversity of small-sized protists in bathypelagic waters. Abundances of heterotrophic nanoflagellates (HNF) and ciliates decrease with depth more steeply than prokaryotes; nonetheless, data indicated that HNF consumed half of prokaryote production in the bathypelagic zone. Aggregates are important habitats for deep-water microbes, which produce more extracellular enzymes (on a per-cell basis) than surface communities. The theory of marine gel formation provides a framework to unravel complex interactions between microbes and organic polymers. Recent data on the effects of hydrostatic pressure on microbial activities indicate that bathypelagic microbial activity is generally higher under in situ pressure conditions than at atmospheric pressures. High-throughput sequencing of 16S rRNA genes revealed a remarkable diversity of Bacteria in the bathypelagic ocean. Metagenomics and comparative genomics of piezophiles reveal not only the high diversity of deep sea microbes but also specific functional attributes of these piezophilic microbes, interpreted as an adaptation to the deep water environment. Taken together, the data compiled on bathypelagic microbes indicate that, despite high-pressure and low-temperature conditions, microbes in the bathypelagic ocean dynamically interact with complex mixtures of organic matter, responding to changes in the ocean's biogeochemical state.
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| 12. |
- Ozturk, M., et al.
(författare)
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Iron enrichment and photoreduction of iron under UV and PAR in the presence of hydroxycarboxylic acid : Implications for phytoplankton growth in the Southern Ocean
- 2004
-
Ingår i: Deep-sea research. Part II, Topical studies in oceanography. - : Elsevier BV. - 0967-0645 .- 1879-0100. ; 51:22-24, s. 2841-2856
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Tidskriftsartikel (refereegranskat)abstract
- Iron(III) photoreduction and the responses of phytoplankton under ultraviolet (UV) and photosynthetically available radiation (PAR) were investigated with the presence of hydroxycarboxylic acid (glucaric acid (GA), a model compound for organic acids excreted by phytoplankton). The incubation experiments were carried out on board using seawater samples collected in the location of the winter ice edge (WIE) and the spring ice edge (SIE) of the Southern Ocean. In this paper, we focus on the results of experiment in WIE. Throughout the experiments, dissolved Fe(II), major nutrients and in vivo fluorescence were monitored regularly. In addition, Chl-a, POC/PON, cell densities of phytoplankton and bacteria, bacterial production, organic peroxide, hydrogen peroxide and total CO2 were measured. The results from the WIE show that iron enrichment had a substantial effect on phytoplankton growth rate. Fe(III) addition in the presence of GA (FeGA) gave higher Fe(II) concentration and higher growth rate of phytoplankton than those in controls. Our results suggest that hydroxycarboxylic acid had a significant chemical and biological impact. The presence of GA influenced iron photochemistry and iron availability to phytoplankton. Phytoplankton growth responses to iron enrichments in incubations under UV and PAR were completely dissimilar. It seems that FeGA addition prominently changes the harmful effect of UV on the phytoplankton population. This study provides preliminary information on how the photoreduction of iron(III) and the phytoplankton growth are affected by iron enrichment in the presence of hydroxycarboxylic acid. © 2004 Elsevier Ltd. All rights reserved.
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| 13. |
- Poulton, Alex J., et al.
(författare)
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Phytoplankton carbon fixation, chlorophyll-biomass and diagnostic pigments in the Atlantic Ocean
- 2006
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Ingår i: Deep-sea research. Part II, Topical studies in oceanography. - : Elsevier BV. - 0967-0645 .- 1879-0100. ; 53:14-16, s. 1593-1610
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Tidskriftsartikel (refereegranskat)abstract
- We have made daily measurements of phytoplankton pigments, size-fractionated (< 2 and > 2-mu m) carbon fixation and chlorophyll-a concentration during four Atlantic Meridional Transect (AMT) cruises in 2003-04. Surface rates of carbon fixation ranged from < 0.2-mmol C m(-3) d(-1) in the subtropical gyres to 0.2-0.5-mmol C m(-3) d(-1) in the tropical equatorial Atlantic. Significant intercruise variability was restricted to the subtropical gyres, with higher chlorophyll-a concentrations and carbon fixation in the subsurface chlorophyll maximum during spring in either hemisphere. In surface waters, although picoplankton (<-mu m) represented the dominant fraction in terms of both carbon fixation (50-70%) and chlorophyll-alpha (80-90%), nanoplankton (> 2-mu m) contributions to total carbon fixation (30-50%) were higher than to total chlorophyll-alpha (10-20%). However, in the subsurface chlorophyll maximum picoplankton dominated both carbon fixation (70-90%) and chlorophyll-alpha (70-90%). Thus, in surface waters chlorophyll-normalised carbon fixation was 2-3 times higher for nanoplankton and differences in picoplankton and nanoplankton carbon to chlorophyll-alpha ratios may lead to either higher or similar growth rates. These low chlorophyll-normalised carbon fixation rates for picoplankton may also reflect losses of fixed carbon (cell leakage or respiration), decreases in photosynthetic efficiency, grazing losses during the incubations, or some combination of all these. Comparison of nitrate concentrations in the subsurface chlorophyll maximum with estimates of those required to support the observed rates of carbon fixation (assuming Redfield stoichiometry) indicate that primary production in the chlorophyll maximum may be light rather than nutrient limited.
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| 14. |
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| 15. |
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| 16. |
- Signori, Camila N., et al.
(författare)
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Spatiotemporal dynamics of marine bacterial and archaeal communities in surface waters off the northern Antarctic Peninsula
- 2018
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Ingår i: Deep-sea research. Part II, Topical studies in oceanography. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0967-0645 .- 1879-0100. ; 149, s. 150-160
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Tidskriftsartikel (refereegranskat)abstract
- Seasonal changes in taxonomic and functional diversity of microbial communities in polar regions are commonly observed, requiring strategies of microbes to adapt to the corresponding changes in environmental conditions. These natural fluctuations form the backdrop for changes induced by anthropogenic impacts. The main goal of this study was to assess the seasonal and temporal changes in bacterial and archaeal diversity and community structure off the northern Antarctic Peninsula over several seasons (spring, summer, autumn) from 2013 to 2015. Ten monitoring stations were selected across the Gerlache and Bransfield Straits and nearby Elephant Island, and archaeal and bacterial communities examined by amplicon sequencing of 16S rRNA genes. Alpha-diversity indices were higher in spring and correlated significantly with temperature. Spring was characterized by the presence of SAR11, and microbial communities remaining from winter, including representatives of Thaumarchaeota (Nimosopurnilus), Euryarchaeota, members of Oceanospirillales, SAR324. Summer and autumn were characterized by a high prevalence of Flavobacteria (NS5 marine group and Polaribacter), Alphaproizobacteria (Rhodobacterales and SAR11 Glade) and Gammaproteobacteria (Oceanospirillales/Balneatrix and Celivibrionales), generally known to be associated with organic matter degradation. Relatively higher abundance of phytoplankton groups occurred in spring, mainly characterized by the presence of the haptophyte Phaeocystis and the diatom Corethron, influencing the succession of heterotrophic bacterial communities. Microbial diversity and community structure varied significantly over time, but not over space, i.e., were similar between monitoring stations for the same time. In addition, the observed interannual variability in microbial community structure might be related to an increase in sea surface temperature. Environmental conditions related to seasonal variation, including temperature and most likely phytoplankton derived organic matter, appear to have triggered the observed shifts in microbial communities in the waters off the northern Antarctic Peninsula.
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| 17. |
- Abrahamsson, Katarina, 1957, et al.
(författare)
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Air-sea exchange of halocarbons: the influence of diurnal and regional variations and distribution of pigments
- 2004
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Ingår i: Deep-Sea Research Part Ii-Topical Studies in Oceanography. - : Elsevier BV. - 0967-0645. ; 51:22-24, s. 2789-2805
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Tidskriftsartikel (refereegranskat)abstract
- Diurnal cycles of halocarbons, except methyl bromide and methyl chloride, were observed at six 24-h stations occupied in three different regions, the Summer Ice Edge, the Winter Ice Edge, and the Antarctic Polar Front, in the Atlantic sector of the Southern Ocean during a Swedish-South African expedition in 1997/1998. The diurnal cycles contained three phases; a productive phase, a phase of losses and a phase with steady state. The duration of the different phases varied for the different stations as well as for individual compounds. The measured production and losses of organo-halogens in the Antarctic Ocean based on values from each station, were in the order of a few to hundreds of Tg yr(-1). Bromochloromethane, tribromomethane, trichloroethene and diiodomethane were the four compounds found in highest concentrations throughout the investigation, and they were found to be the major contributors of organohalogens. Only the presence of the photosynthetic pigment 19'-hexanoyloxyfucoxanthin, biomarker pigment of haptophytes, could explain some of the variations in the distribution and production of halocarbons, and then only for iodinated compounds. The flux of organo-halogens from the oceans to the atmosphere was estimated in two ways, either based on calculations according to models or based on the measured concentrations. Large discrepancies were found, which could not be explained by chemical or biological degradation or adsorption to particles. This investigation, therefore, shows the need for assessing the rates of degradation and the air-sea exchange more accurately. (C) 2004 Elsevier Ltd. All rights reserved.
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| 18. |
- Abrahamsson, Katarina, 1957, et al.
(författare)
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Variations of biochemical parameters along a transect in the Southern Ocean, with special emphasis on volatile halogenated organic compounds
- 2004
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Ingår i: Deep-sea research. Part II, Topical studies in oceanography. - : Elsevier BV. - 0967-0645. ; 51:22-24, s. 2745-2756
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Tidskriftsartikel (refereegranskat)abstract
- A number of parameters of biogeochemical interest were monitored along a north-southerly transect (S 43-S 63degrees) in the Atlantic Sector of the Southern Ocean from the 8th to the 20th of December 1997. Changes in total dissolved inorganic carbon (C-T) and total alkalinity (A(T)) were mostly dependent on temperature and salinity until the ice edge was reached. After this point only a weak correlation was seen between these. Highest mean values of C-T and A(T) were observed in the Winter Ice Edge (WIE) (2195 and 2319 mumol kg(-1), respectively). Lowest mean AT (2277 mumol kg(-1)) was observed in the Sub-Antarctic Front (SAF), whereas lowest mean CT concentration (2068 mumol kg(-1)) was associated with the Sub-Tropical Front (STF). The pH in situ varied between 8.060 and 8.156 where the highest values were observed in the southern part of the Antarctic Polar Front (APF) and in the Summer Ice Edge (SIE) Region. These peaks were associated with areas of high chlorophyll a (chl a) and tribromomethane values. In the other areas the pH in situ was mainly dependent on hydrography. Bacterial abundance decreased more than one order of magnitude when going from north to south. The decrease appeared to be strongly related to water temperature and there were no elevated abundances at frontal zones. Microphytoplankton dominated in the SAF and APF, whereas the nano- and picoplankton dominated outside these regions. Volatile halogenated compounds were found to vary both with regions, and with daylight. For the iodinated compounds, the highest concentrations were found north of the STF. Brominated hydrocarbons had high concentrations in the STF, but elevated concentrations were also found in the APF and SIE regions. No obvious correlation could be found between the occurrence of individual halocarbons and chl a. On some occasions trichloroethene and tribromomethane related to the presence of nano- and microplankton, respectively.
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| 19. |
- Bromhead, D., et al.
(författare)
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The potential impact of ocean acidification on eggs and larvae of the Yellowfin Tuna.
- 2015
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Ingår i: Deep-sea research. Part II, Topical studies in oceanography. - : Elsevier BV. - 0967-0645. ; 113, s. 268-279
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Tidskriftsartikel (refereegranskat)abstract
- Anthropogenic carbon dioxide (CO2) emissions are resulting in increasing absorption of CO2 by the earth's oceans, which has led to a decline in ocean pH, a process known as ocean acidification (OA). Evidence suggests that OA may have the potential to affect the distribution and population dynamics of many marine organisms. Early life history processes (e.g. fertilization) and stages (eggs, larvae, juveniles) may be relatively more vulnerable to potential OA impacts, with implications for recruitment in marine populations. The potential impact of OA upon tuna populations has not been investigated, although tuna are key components of pelagic ecosystems and, in the Pacific Ocean, form the basis of one of the largest and most valuable fisheries in the world. This paper reviews current knowledge of potential OA impacts on fish and presents results from a pilot study investigating how OA may affect eggs and larvae of yellowfin tuna, Thunnus albacares. Two separate trials were conducted to test the impact of pCO2 on yellowfin egg stage duration, larval growth and survival. The pCO2 levels tested ranged from present day ($400 μatm) to levels predicted to occur in some areas of the spawning habitat within the next 100 years (o2500 μatm) to 300 years ($ o5000 μatm) to much more extreme levels ($10,000 μatm). In trial 1, there was evidence for significantly reduced larval survival (at mean pCO2 levelsZ4730 μatm) and growth (at mean pCO2 levels Z 2108 μatm), while egg hatch time was increased at extreme pCO2 levelsZ10,000 μatm (nintermediate levels were not tested). In trial 2, egg hatch times were increased at mean pCO2 levelsZ1573 μatm, but growth was only impacted at higher pCO2 (Z8800 μatm) and there was no relationship with survival. Unstable ambient conditions during trial 2 are likely to have contributed to the difference in results between trials. Despite the technical challenges with these experiments, there is a need for future empirical work which can in turn support modeling-based approaches to assess how OA will affect the ecologically and economically important tropical tuna resources.
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| 20. |
- Chen, Deliang, 1961, et al.
(författare)
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Attenuation of biologically effective UV doses under overcast skies: a case study from the eastern Atlantic sector of the Southern Ocean
- 2004
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Ingår i: Deep-Sea Research Part Ii-Topical Studies in Oceanography. - : Elsevier BV. - 0967-0645. ; 51:22-24, s. 2673-2682
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Tidskriftsartikel (refereegranskat)abstract
- This study deals attenuation of ultraviolet solar radiation measured during the SWEDARP 1997/1998 expedition in the eastern Atlantic sector of the Southern Ocean. Experimental data were measured on board a ship and theoretical computation of radiative transfer has been applied. Focus has been placed on biologically effective UV-B doses using three commonly applied biological weighting functions based on: inhibition of carbon dioxide fixation (Science 258 (1992) 646); Generalized plant effects (Stratospheric Ozone Reduction, Solar Ultraviolet Radiation and Plant Life 1986, Springer, Berlin) and DNA lesions (Proc. Nat. Acad. Sci. USA 71 (1974) 3363). The ratio of measured dose to that under clear sky condition, calculated by a model, was defined as transmittance which was studied in relation to other information. Further, the interrelationship between the biologically effective UV doses and various broadband irradiance in the UV-A, UV-B and PAR was established. It shows that the UV-B doses based on the three weighting functions are closely linked to each other and their cloud transmittances are nearly the same. The biologically effective UV-B doses can be estimated with reasonable accuracy from the broadband irradiance in the UV-A, UV-B and PAR regions, with UV-B giving the best results. Univariate analysis between the transmittance and zenith angle, total cloud cover and cloud base height was performed. It is found that attenuation is almost independent of zenith angle. Transmission is reduced by 7.7% if the cloud cover is increased by one octa. The average transmittance of the UV-B doses is 0.40, indicating that clouds have played an important role in reducing the UV radiation. (C) 2004 Elsevier Ltd. All rights reserved.
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| 21. |
- Chierici, Melissa, 1968, et al.
(författare)
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Algorithms to estimate carbon dioxide in the upper subarctic North Atlantic using observations, satellite and ocean analysis data
- 2009
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Ingår i: Deep-sea research. Part II, Topical studies in oceanography. - : Elsevier BV. - 0967-0645. ; 56, s. 630-639
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Tidskriftsartikel (refereegranskat)abstract
- Observations of the surface-water fugacity of carbon dioxide (fCO2sw) measured during 2005 in the subpolar North Atlantic Ocean (58–62°N, 10–40°W) were used together with in situ ocean data and remotely sensed data to develop algorithms to estimate fCO2sw. Based on multiple regression we found that sea-surface temperature (SST), mixed-layer depth (MLD), and chlorophyll a (chl a) contributed significantly to the fit. Two algorithms were developed for periods depending on the presence of chl a data. The correlation coefficient (r2) and the root-mean-square deviation (rms) for the best fit in the period when chl a was observed (20 March–15 October) were 0.720 and ±10.8 μatm, respectively. The best fit for the algorithm for the period when no chl a was present (16 October–19 March) resulted in a r2 of 0.774 and a rms of ±5.6 μatm. Based on these algorithms we estimated seasonal fields of fCO2sw and the air–sea CO2 flux. The estimated net annual CO2 sink was 0.0058 Gt C yr−1 or 0.6 mol C m−2 yr−1.
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| 22. |
- Chierici, Melissa, 1968, et al.
(författare)
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Biogeochemical evolution of the carbon dioxide system in the waters of long-lived mesoscale eddies in the Northeast Pacific Ocean
- 2005
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Ingår i: Deep-Sea Research Part Ii-Topical Studies in Oceanography. - : Elsevier BV. - 0967-0645. ; 52:7-8, s. 955-974
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Tidskriftsartikel (refereegranskat)abstract
- An anticyclonic eddy, named Haida-2000, formed off the Southern Queen Charlotte Islands early in the year 2000. The eddy subsequently tracked northwest, transporting fresh, warm, and nutrient-rich water into the Northeast Pacific Ocean. Based on total dissolved inorganic carbon (CA total alkalinity (AT), and nutrients from six seasonal cruises between February 2000 and September 2001, we found that the oceanic carbonate system of the Surface waters in the eddy changed significantly. The greatest loss of C-T from the surface waters of Haida-2000 occurred during the first year, between February and June 2000. Based oil a concomitant loss in nitrate (NO3), the large CT loss we observed was likely due to biological production of organic carbon and probably resulted in a large drawdown of atmospheric CO,, as supported by the observed fugacity of carbon dioxide (fCO(2)) in the surface waters. During fall, C-T, fCO(2), and NO3 values increased, probably due to oxidation of organic matter and vertical entrainment Of CT and nutrient-rich water from below with fall mixing. As a result, the surface waters of the eddy were highly oversaturated in CO2 relative to the atmosphere. Another Haida eddy (Haida-2001) had a significantly smaller nitrate drawdown than Haida-2000 during its first spring, but the CT losses were similar in the two eddies. In early summer (mid-June) of the second year, the surface and sub-surface waters in Haida-2000 gained C-T, A(T), and NO3, partly caused by a merging with another 2001 Haida eddy, showing that exchange with surrounding waters took place and was significant at times. The high nitrate/ low chlorophyll (HNLC) surface waters at Ocean Station Papa (OSP), showed less fCO(2) Undersaturation during summer and less total nitrate and CT loss than Haida-2000, indicating that both eddies were larger sinks for carbon lthan HNLC waters. The waters surrounding the eddies generally had concentrations of C-T, A(T), and NO3 that were similar to or slightly higher than the waters of both Haida eddies throughout the study. Also, the sub-surface waters in these eddies showed no significant change in total carbon content, suggesting that at these depths eddies are recycling, not exporting systems. (c) 2005 Elsevier Ltd. All rights reserved.
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| 23. |
- Chierici, Melissa, 1968, et al.
(författare)
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Variability in pH, fCO(2), oxygen and flux of CO2 in the surface water along a transect in the Atlantic sector of the Southern Ocean
- 2004
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Ingår i: Deep-Sea Research Part Ii-Topical Studies in Oceanography. - : Elsevier BV. - 0967-0645. ; 51:22-24, s. 2773-2787
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Tidskriftsartikel (refereegranskat)abstract
- Underway sampling and measurements of pH, fCO(2), oxygen and Chlorophyll a (Chl a) were performed in the surface waters from Cape Town (South Africa) to Queen Maud Land (Antarctica) in the Atlantic sector of the Southern Ocean during the austral summer 1997/1998. From direct measurements of these parameters and from calculated fCO(2) the oceanic carbon dioxide system was studied and related to hydrological and biological parameters. fCO(2) was in general undersaturated relative to the atmosphere and showed a large variability with values ranging from 313 to 377 muatm with a mean value of 346 +/- 13 muatm. The undersaturation was more pronounced in areas associated with fronts where high Chl a and high pH in situ values were observed. Using shipboard wind speed data, estimates of the CO2 flux were made along the transect and during three mesoscale surveys on the northward return transect in the area of the Spring Ice Edge (SIE), the Winter Ice Edge (WIE) and in the Antarctic Polar Front (APF). The undersaturation observed during the transect caused the ocean to act as a sink for CO2 with a mean sea-air flux for the entire transect of -3+/-5 mmol m(-2) d(-1) with a large variability between -20 mmol m(-2) d(-1) (oceanic uptake) to 1.3 mmol m(-2) d(-1) (oceanic source). The lowest fCO(2) values (largest oceanic uptake Of COD were found at the southern boundary of the APF at 53degreesS, which coincided with a supersaturation in oxygen and high pH values. Oxygen concentrations were measured from 50degreesS to 63degreesS and varied between 324 and 359 mumol kg(-1) with a mean value of 347 +/- 9 mumol kg(-1). In general only small deviations from equilibrium oxygen saturation were observed (mean value = 99+/-2%). However, in the SIE oxygen was clearly undersaturated, probably an effect of upwelling of oxygen poor deep water which had not yet been compensated for by biological production. Three weeks later, the ice edge had retreated in the SIE region and the Chl a concentration had increased three-fold, suggesting the start of a phytoplankton bloom. This was also seen in the oxygen concentration which had increased and showed supersaturation. This coincided with an increased oceanic uptake of CO2 in the SIE during the mesoscale survey. (C) 2004 Elsevier Ltd. All rights reserved.
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| 24. |
- Croot, P. L., et al.
(författare)
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The distribution and specification of iron along 6 degrees E in the Southern Ocean
- 2004
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Ingår i: Deep-Sea Research Part Ii-Topical Studies in Oceanography. - : Elsevier BV. - 0967-0645. ; 51:22-24, s. 2857-2879
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Tidskriftsartikel (refereegranskat)abstract
- The distribution and speciation of iron was determined along a transect in the eastern Atlantic sector (6degreesE) of the Southern Ocean during a collaborative Scandinavian/South African Antarctic cruise conducted in late austral summer (December 1997/January 1998). Elevated concentrations of dissolved iron (>0.4 nM) were found at 60degreesS in the vicinity of the Spring Ice Edge (SIE) in tandem with a phytoplankton bloom, chiefly dominated by Phaeocystis sp. This bloom had developed rapidly after the loss of the seasonal sea ice cover. The iron that fuelled this bloom was mostly likely derived from sea ice melt. In the Winter Ice Edge (WIE), around 55degreesS, dissolved iron concentrations were low (<0.2 nM) and corresponded to lower biological productivity, biomass. In the Antarctic Polar Front, at approximately 50degreesS, a vertical profile of dissolved iron showed low concentrations (<0.2 nM); however, a surface survey showed higher concentrations (1-3 nM), and considerable patchiness in this dynamic frontal region. The chemical speciation of iron was dominated by organic complexation throughout the study region. Organic iron-complexing ligands ([L]) ranged from 0.9 to 3.0 nM Fe equivalents, with complex stability log K'(FeL) = 21.4-23.5. Estimated concentrations of inorganic iron (Fe') ranged from 0.03 to 0.79 pM, with the highest values found in the Phaeocystis bloom in the SIE. A vertical profile of iron-complexing ligands in the WIE showed a maximum consistent with a biological source for ligand production and near surface minimum possibly consistent with loss via photodecomposition. This work further confirms the role iron that has in the Southern Ocean in limiting primary productivity. (C) 2004 Elsevier Ltd. All rights reserved.
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| 25. |
- Figueroa, Rosa, et al.
(författare)
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From homothally to heterothally; mating preferences and genetic variation within clones of the dinoflagellate Gymnodinium catenatum
- 2010
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Ingår i: Deep-Sea Research. Part Ii, Topical Studies in Oceanography. - : Elsevier BV. - 0967-0645. ; 57:3-4, s. 190-198
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Tidskriftsartikel (refereegranskat)abstract
- The chain-forming dinoflagellate Gymnodinium catenatum Graham is responsible for outbreaks of paralytic shellfish poisoning (PSP), a human health threat in coastal waters. Sexuality in this species is of great importance in its bloom dynamics, and has been shown to be very complex but lacks an explanation. For this reason, we tested if unreported homothallic behavior and rapid genetic changes may clarify the sexual system of this alga. To achieve this objective, 12 clonal strains collected from the Spanish coast were analyzed for the presence of sexual reproduction. Mating affinity results, self-compatibility studies, and genetic fingerprinting (amplified fragment length polymorphism, AFLP) analysis on clonal strains, showed three facts not previously described for this species: (i) That there is a continuous mating system within G. catenatum, with either self-compatible strains (homothallic), or strains that needed to be outcrossed (heterothallic), and with a range of differences in cyst production among the crosses. (ii) There was intraclonal genetic variation, i.e. genetic variation within an asexual lineage. Moreover, the variability among homothallic clones was smaller than among the heterothallic ones. (iii) Sibling strains (the two strains established by the germination of one cyst) increased their intra- and inter-sexual compatibility with time. To summarize, we have found that G. catenatum's sexual system is much more complex than previously described, including complex homothallic/heterothallic behaviors. Additionally, high rates of genetic variability may arise in clonal strains, although explanations for the mechanisms responsible are still lacking. (C) 2009 Elsevier Ltd. All rights reserved.
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| 26. |
- Fransson, Agneta, 1964, et al.
(författare)
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Diurnal variability in the oceanic carbon dioxide system and oxygen in the Southern Ocean surface water
- 2004
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Ingår i: Deep-Sea Research Part Ii-Topical Studies in Oceanography. - : Elsevier BV. - 0967-0645. ; 51:22-24, s. 2827-2839
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Tidskriftsartikel (refereegranskat)abstract
- During the SWEDARP cruise to the Atlantic sector of the Southern Ocean 1997/1998 six 24-hour stations were occupied in the areas of the Spring Ice Edge (SIE1, SIE2 and SIE3), the Winter Ice Edge (WIE), and the Antarctic Polar Front (APF1 and APF2). Samples were taken at the surface (2 m) every second hour and analyzed for total dissolved inorganic carbon, total alkalinity, pH and dissolved oxygen. By the use of wind speed measurements, calculated fugacity of carbon dioxide, fCO(2), and oxygen concentrations in the surface water, sea-air fluxes of carbon dioxide (CO2) and oxygen were calculated. These fluxes and the diurnal change in the chemical properties are discussed in relation to changes in biological activity. The fluctuations in wind speed showed a larger impact on the variability of the calculated fluxes than the fluctuations in surface water fCO(2) or oxygen saturation. The calculated fluxes and the variability also showed large differences depending on how the wind speed was used, instantaneously or averaged over 24 hours. The calculated sea-air CO2 fluxes using instantaneous wind speed varied between -0.012 and -0.11 mmol m(-2) h(-1) in the SIE1, -0.0073 and -0.30 mmol m(-2) h(-1) in the WIE and -0.043 and -1.65 mmol m(-2) h(-1) in the APF2. The mean values of sea-air CO2 fluxes were calculated to -0.046+/-0.044, -0.10+/-0.094 and -0.52+/-0.64 mmol m(-2) h(-1) for the SIE1, WIE and the APF2, respectively. The mean values of sea-air oxygen fluxes were calculated to 0.072+/-0.073, -0.12+/-0.54 and 1.4+/-1.3 mmol m(-2) h(-1) for the corresponding regions. (C) 2004 Elsevier Ltd. All rights reserved.
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| 27. |
- Fransson, Agneta, 1964, et al.
(författare)
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Transformation of carbon and oxygen in the surface layer of the eastern Atlantic sector of the Southern Ocean
- 2004
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Ingår i: Deep-Sea Research Part Ii-Topical Studies in Oceanography. - : Elsevier BV. - 0967-0645. ; 51:22-24, s. 2757-2772
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Tidskriftsartikel (refereegranskat)abstract
- The biogeochemical transformation of carbon, and the exchange of carbon dioxide and oxygen over the sea-air interface were evaluated from measurements of dissolved inorganic carbon, total alkalinity, dissolved oxygen and nitrate in the Atlantic sector of the Southern Ocean. The investigation was carried out. along longitude 6degreesE from December 1997 to January 1998 and was focused on three areas; the Spring Ice Edge (SIE), the Winter Ice Edge (WIE) and the Antarctic Polar Front (APF). The method is based on the assumption that differences between preformed and measured concentration of any property, are attributable to biological processes and sea-air exchange. By correcting the deficit of carbon and excess of oxygen observed in the surface mixed layer for the biological activity, the sea-air exchange of carbon dioxide and oxygen is estimated. In the SIE and the APF, a net release of carbon dioxide to the atmosphere of 0.1 and 0.5 mol m(-2), respectively, was calculated over a time scale of several months (from austral winter to January). In the WIE a net oceanic uptake of carbon dioxide was calculated, with a sea-air exchange of -0.1 mol m(-2). The calculated sea-air exchange of oxygen in the APF indicated an oceanic net release of oxygen to the atmosphere of 1.2 mol m(-2). In the SIE and the WIE the sea-air exchange of oxygen was -0.3 and -1.4 mol m(-2), respectively, from austral winter to January. Averaging the integrated sea-air exchanges indicated that the entire region acted as a weak oceanic source of carbon dioxide, from austral winter to January. The corresponding oxygen sea-air exchange showed a sink. (C) 2004 Elsevier Ltd. All rights reserved.
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| 28. |
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| 29. |
- Granéli, Wilhelm, et al.
(författare)
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Bacterial abundance, production and organic carbon limitation in the Southern Ocean (39-62 degrees S, 4-14 degrees E) during the austral summer 1997/1998
- 2004
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Ingår i: Deep-Sea Research. Part Ii, Topical Studies in Oceanography. - : Elsevier BV. - 0967-0645. ; 51:22-24, s. 2569-2582
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Tidskriftsartikel (refereegranskat)abstract
- Bacterial abundance and production were studied in different zones in the Southern Ocean (39-62degreesS, 4-14degreesE) during a cruise in December-January 1997/1998. The role of potential growth limitation of bacteria due to limited availability of organic carbon (glucose) or inorganic N and P was studied in parallel. A positive correlation between surface water temperatures (-2 to 18 degreesC) and bacterial abundance (< 0. 1 X 10(6)-1.5 x 10(6) cells ml(-1)) was observed. Bacteria were studied in vertical profiles, concentrated to three areas close to 6degreesE: the former Spring Ice Edge (SIE, 60degreesS, high chlorophyll a), the former Winter Ice Edge (WIE, 56degreesS, low chlorophyll a) and the Antarctic Polar Front at 51degreesS (APF, moderate chlorophyll a levels). Bacterial abundance was uniformly low south of the APF, and for the upper 50 m generally below 0.3 x 10(6) bacterial ml(-1). In deeper water, bacterial abundance decreased dramatically for WIE and APF stations, but less markedly for SIE stations. The average volumetric bacterial production in the mixed layer was highest for APF stations (0.04 mug Cl-1 h(-1)), but only half of this value for SIE stations (0.02 mug Cl-1 h(-1)), with WIE in between (approximately 0.03 mug Cl-1 h(-1)). Below 100 m, bacterial production decreased to values close to the detection limit. None of the three areas demonstrated any systematic diurnal variations in bacterial production in surface water (2 m) or at the chlorophyll maximum (situated between 30 and 66 m). We observed a positive correlation between bacterial production and in vivo chlorophyll a fluorescence, but there was no correlation between this parameter and bacterial abundance, possibly indicating different control mechanisms for these two parameters. Unfiltered water samples from 20 m depth were incubated at in situ temperatures and amended with ammonium, phosphate or glucose. In all the three experiments, from warm waters (relatively poor in inorganic nitrogen and phosphorus) south of Cape Town (38degreesS, + 18.6 degreesC), in the colder and inorganic nutrient-rich waters north of the APF (45degreesS, + 7.0 degreesC) as well as in the cold, nutrient-rich waters at the SIE (61 degreesS, -0.13 degreesC), organic carbon additions resulted in a significant increase in bacterial production. Bacterial growth rates were very different between the three regions, and the growth response in the bacterial communities to the carbon additions was very slow at low temperatures. (C) 2004 Elsevier Ltd. All rights reserved.
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| 30. |
- Kalén, Ola, 1971, et al.
(författare)
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Is the oceanic heat flux on the central Amundsen Sea shelf caused by barotropic or baroclinic currents?
- 2016
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Ingår i: Deep-sea research. Part II, Topical studies in oceanography. - : Elsevier BV. - 0967-0645. ; 123, s. 7-15
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Tidskriftsartikel (refereegranskat)abstract
- The glaciers that drain the West Antarctic Ice Sheet into the Amundsen Sea are accelerating and experiencing increased basal melt of the floating ice shelves. Warm and salty deep water has been observed to flow southward in deep troughs leading from the shelf break to the inner shelf area where the glaciers terminate. It has been suggested that the melting induced by this warm water is responsible for the acceleration of the glaciers. Here we investigate the structure of the currents and associated heat flow on the shelf using in-situ observations from 2008 to 2014 from Dotson Trough, the main channel in the western part of the Amundsen Sea shelf, and output from a numerical model. The model is generally able to reproduce the observed velocities and temperatures in the trough, albeit with a thicker warm bottom layer. In the absence of measurements of sea surface height we define the barotropic component of the flow as the vertical average of the velocity. It is shown that the flow is dominated by warm barotropic inflows on the eastern side and colder and fresher barotropic outflows on the western side. The transport of heat appears to be primarily induced by this clockwise barotropic circulation in the trough, contrary to earlier studies emphasizing a bottom-intensified baroclinic inflow as the main contributor.
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| 31. |
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| 32. |
- Miles, T., et al.
(författare)
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Glider observations of the Dotson Ice Shelf outflow
- 2016
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Ingår i: Deep-Sea Research Part Ii-Topical Studies in Oceanography. - : Elsevier BV. - 0967-0645. ; 123, s. 16-29
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Tidskriftsartikel (refereegranskat)abstract
- The Amundsen Sea is one of the most productive polynyas in the Antarctic per unit area and is undergoing rapid changes including a reduction in sea ice duration, thinning ice sheets, retreat of glaciers and the potential collapse of the Thwaites Glacier in Pine Island Bay. A growing body of research has indicated that these changes are altering the water mass properties and associated biogeochemistry within the polynya. Unfortunately difficulties in accessing the remote location have greatly limited the amount of in situ data that has been collected. In this study data from a Teledyne-Webb Slocum glider was used to supplement ship-based sampling along the Dotson Ice Shelf (DIS). This autonomous underwater vehicle revealed a detailed view of a meltwater laden outflow from below the western flank of the DIS. Circumpolar Deep Water intruding onto the shelf drives glacial melt and the supply of macronutrients that, along with ample light, supports the large phytoplankton blooms in the Amundsen Sea Polynya. Less well understood is the source of micronutrients, such as iron, necessary to support this bloom to the central polynya where chlorophyll concentrations are highest. This outflow region showed decreasing optical backscatter with proximity to the bed indicating that particulate matter was sourced from the overlying glacier rather than resuspended sediment. This result suggests that particulate iron, and potentially phytoplankton primary productivity, is intrinsically linked to the magnitude and duration of sub-glacial melt from Circumpolar Deep Water intrusions onto the shelf.
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| 33. |
- Pierrot, D., et al.
(författare)
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Recommendations for autonomous underway pCO2 measuring systems and data-reduction routines
- 2009
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Ingår i: Deep-Sea Research II. - : Elsevier BV. - 0967-0645. ; 56:8-10, s. 512-522
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Tidskriftsartikel (refereegranskat)abstract
- In order to facilitate the collection of high quality and uniform surface water pCO2 data, an underway pCO2 instrument has been designed based on community input and is now commercially available. Along with instrumentation, agreements were reached on data reduction and quality control that can be easily applied to data from these systems by using custom-made freeware. This new automated underway pCO2 measuring system is designed to be accurate to within 0.1 μatm for atmospheric pCO2 measurements and to within 2 μatm for seawater pCO2, targeted by the scientific community to constrain the regional air–sea CO2 fluxes to 0.2 Pg C year−1. The procedure to properly reduce the underway pCO2 data and perform the steps necessary for calculation of the fugacity of CO2 from the measurements is described. This system is now widely used by the scientific community on many different types of ships. Combined with the recommended data-reduction procedures, it will facilitate producing data sets that will significantly decrease the uncertainty currently present in estimates of air–sea CO2 fluxes.
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| 34. |
- Rasmus, K. E., et al.
(författare)
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Optical studies in the Southern Ocean
- 2004
-
Ingår i: Deep-Sea Research Part Ii-Topical Studies in Oceanography. - : Elsevier BV. - 0967-0645. ; 51:22-24, s. 2583-2597
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Tidskriftsartikel (refereegranskat)abstract
- During the Austral summer of 1997-1998, measurements of absorption, attenuation, downwelling and upwelling irradiance were made in the Southern Ocean along a S-N transect at 6degreesE. Measurements were made to quantify the penetration of ultraviolet B radiation (UVBR) in the water column and daily doses of UVBR at different water depths, to study the attenuation of photosynthetically active radiation (PAR), and to judge if in the investigated areas of the Southern Ocean phytoplankton are light limited. The results show that the UVBR affects a substantial portion of the upper mixed layer. The diffuse attenuation coefficients (K-PAR) for PAR were found to vary between 0.03 and 0.09 m(-1). Using the values for KPAR and the definition of the Sverdrup critical depth, the studied Southern Ocean plankton systems were found not to be light limited. (C) 2004 Elsevier Ltd. All rights reserved.
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| 35. |
- Singh, Arvind, et al.
(författare)
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Revisiting N-2 fixation in the North Atlantic Ocean: Significance of deviations from the Redfield Ratio, atmospheric deposition and climate variability
- 2013
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Ingår i: Deep-Sea Research Part Ii-Topical Studies in Oceanography. - : Elsevier BV. - 0967-0645. ; 93, s. 148-158
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Tidskriftsartikel (refereegranskat)abstract
- The average oceanic nitrate-to-phosphate molar ratio (NO3-:PO43-approximate to 16:1, referred to as the Redfield Ratio) in subsurface waters, which is similar to the average ratio of particulate nitrogen (N)-to-phosphorus (P) in phytoplankton, is the cornerstone in calculating geochemical estimates of N-2 fixation and denitrification rates. Any deviations from this canonical Redfield Ratio in intermediate ocean waters, expressed as N* (a measure of NO3- in excess or deficit of 16 x PO43-), provides an integrated estimate of net N fluxes into and out of the ocean. In well-oxygenated ocean basins such as the North Atlantic Ocean, N* estimates are usually positive and can be used to infer that rates of N-2 fixation exceed rates of denitrification. We use this approach to estimate N-2 fixation over the last two decades (1988-2009) based on data collected at the Bermuda Atlantic Time-series Study (BATS) site in the North Atlantic Ocean near Bermuda. Our results indicate that interpretation of the N* tracer as an estimate of N-2 fixation should be undertaken with caution, as N-2 fixation is not the only process that results in a positive N* estimate. The impacts of a locally variable nitrogen-to-phosphorus ratio, relative to the fixed Redfield Ratio, in the suspended particulate matter as well as in the subsurface water nutrients and atmospheric N deposition on N* variability were examined. Furthermore, we explored the role of climate modes (i.e., North Atlantic Oscillation and Arctic Oscillation) on N* variability. We found that N* in the subsurface waters was significantly affected by these factors and hence previous estimates of N-2 fixation using this technique might have been substantially overestimated. Our revised estimate of N-2 fixation in the North Atlantic Ocean (0 degrees N-50 degrees N, 20 degrees W-80 degrees W) is 12.2 +/- 0.9 x 10(11) mol N yr(-1), and based on long-term BATS data provides better constraints than both earlier indirect and direct estimates N-2 fixation. (C) 2013 Elsevier Ltd. All rights reserved.
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| 36. |
- Turner, David R., 1951, et al.
(författare)
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The SWEDARP 1997/98 marine expedition: overview
- 2004
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Ingår i: Deep-Sea Research Part Ii-Topical Studies in Oceanography. - : Elsevier BV. ; 51, s. 2745-2756.
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Tidskriftsartikel (refereegranskat)abstract
- The SWEDARP 1997/98 expedition aboard the S.A. Agulhas focused on three study areas along the 6degreesE meridian: 60degreesS, the location of the spring ice edge; 56degreesS, the location of the winter ice edge; and 50.5degreesS, the Antarctic Polar Front. This intensive study was preceded by a north-south transect through the area measuring surface water properties while under way. An extensive measurement programme included hydrography, tracers, nutrients, organic carbon, trace metals, bacteria, and primary and secondary producers (including production and grazing rates). Analysis of the results from the three study areas does not identify a single factor limiting primary production: water column stability and the optical regime, and probably iron supply contributed to the control of primary production. The study area acted as a sink for atmospheric CO2 at the time of measurement, while analysis of water column carbon inventories indicated a net CO2 source integrated over the spring season. (C) 2004 Elsevier Ltd. All rights reserved.
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| 37. |
- Wulff, Angela, 1963, et al.
(författare)
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Spatial and vertical distribution of phytoplankton pigments in the eastern Atlantic sector of the Southern Ocean
- 2004
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Ingår i: Deep-Sea Research Part Ii-Topical Studies in Oceanography. - : Elsevier BV. - 0967-0645. ; 51:22-24, s. 2701-2713
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Tidskriftsartikel (refereegranskat)abstract
- The spatial and vertical distribution of phytoplankton pigments was analysed during the Scandinavian/South African Southern Ocean JGOFS expedition of the S.A. Agulhas from 31 December 1997 to 26 January 1998. In total, seawater from 12 different stations along a transect at 6degreesE from 60.38 to 49.82degreesS were sampled at water depths of approximately 2, 10, 20, 30, 50, 75 and 100 m. Pigment concentrations were analysed using high-performance liquid chromatography. The highest chlorophyll a (chl a) concentrations were found within the Spring Ice Edge (SIE) at water depths of 2-30 m (1.5-2.0 mug l(-1)). The lowest phytoplankton biomass (chl a) was found within the Winter Ice Edge (WIE) with typical values around 0.3 mug l(-1). While the chl a concentrations decreased with depth within the SIE, no apparent difference between depths was found within WIE. The same trend with similar chl a concentrations (0.8-1.2 mug l(-1)) at all depths was found for the northernmost part of the Antarctic Polar Front (APF) except for samples from 100 m. Principal component analysis (PCA) and the matrix factorisation program, CHEMTAX, were used to interpret the pigment data. The PCA indicated small differences between the samples in WIE and APF, while the SIE samples were separated into three groups. At the southernmost stations a clear separation was found between surface samples and deeper samples; this was not seen at the two northernmost stations within SIE. Along the whole transect, CHEMTAX suggested a dominance of diatoms and haptophytes. In general, the haptophytes contributed more to total chl a further south and the diatom contribution increased from south to north. Within WIE, CHEMTAX indicated that cyanobacteria were contributing approximately 3% to the total autotrophic biomass. In APF, a more diverse phytoplankton community was found compared with WIE and SIE. The pigment patterns interpreted by CHEMTAX showed that different phytoplankton assemblages were associated with distinct water masses along the transect. (C) 2004 Elsevier Ltd. All rights reserved.
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| 38. |
- Wängberg, Sten-Åke, 1955, et al.
(författare)
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Impact of ultraviolet-B radiation on the development of phytoplankton communities in the eastern Atlantic sector of the Southern Ocean - results from on-deck model ecosystem experiments
- 2004
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Ingår i: Deep-Sea Research Part Ii-Topical Studies in Oceanography. - : Elsevier BV. - 0967-0645. ; 51:22-24, s. 2731-2744
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Tidskriftsartikel (refereegranskat)abstract
- Two model ecosystem experiments to assess the effects of UVB radiation (UVBR, 280-320 nm) on phytoplankton communities were performed on-deck during the SWEDARP 97/98 expedition to the eastern Atlantic sector of the Southern Ocean in January 1998. The first experiment was run in the Spring Ice Edge, around 60degreesS, and the second at the Antarctic Polar Front, around 50degreesS. The duration of the experiments were 12 and 10 days, respectively. Ambient UVBR was modified to three levels (i.e. treatments): NoUVB-shielded from UVBR (mylar foil); AMB-ambient UVBR; UVB+--enhanced UVBR. The development of the phytoplankton communities was followed by measuring primary production and composition of pigments and diatom species. At the start of the first experiment UVB+ had lower primary production per volume, but not when normalised to chlorophyll a. At the end there were no differences between treatments in primary production per volume but there were differences when normalised to chlorophyll a. In addition, a significant increase in the stimulation of primary production for UVB+ when excluding UVBR and in chlorophyll a concentration was found. These changes, together with changes in species composition, are assumed to be the result of an adaptation to the enhanced UVBR. During the second experiment, the effects from changes in UVBR were generally smaller but resembled to some extent the first experiment. The chlorophyll a concentration increased significantly in the UVB+ treatment at the end of the experiment and there was a strong tendency towards a reduction in primary production per chlorophyll a, but not per volume. The results are important when estimating the effects of increased UVBR as they show variability in short-term sensitivity, and also the capacity of phytoplankton communities to adapt to UVBR and retain primary production even in enhanced UVBR. (C) 2004 Elsevier Ltd. All rights reserved.
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| 39. |
- Harash, Fayez, et al.
(författare)
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3-D density structure of the upper-mantle in the eastern Mediterranean Sea and surrounding region using gravity inversion constrained by seismic velocity model
- 2023
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Ingår i: Tectonophysics. - : Elsevier. - 0040-1951 .- 1879-3266. ; 860
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Tidskriftsartikel (refereegranskat)abstract
- A 3D density structure of the lithosphere and upper mantle beneath the eastern Mediterranean Sea (EMS) and its adjacent region was constructed based on gravity anomaly inversion constrained by a seismic tomography model. Gravity effects of terrain and crust were removed from the observed gravity field (EIGEN-6C4) to obtain the residual mantle gravity anomaly (RMGA). The density distribution of the lithosphere and upper mantle was investigated. The 3D inversion process was constrained by an initial density model projected from the shear-wave velocity model (SL2013sv). The results show some characteristics of the density distribution in the lithosphere and in the upper mantle that could be related to the tectonic importance of the Mediterranean Sea and the surrounding region. A low-density zone dominates the lithosphere beneath the Sea except for the area around the Arabia Shield and North Anatolian Fault belt. A thinner, high-density layer beneath the southwest of the Sea may be related to the older oceanic lithospheric fragments. The high-density anomalies appear at depths below 280 km beneath the Sea and the Turkish Aegean Sea Plate. However, the low-density anomalies appear on the upper mantle under the trenches of the southwestern part of the Mediterranean Sea, the eastern part of the Aegean Sea, the Red Sea, the Black Sea, and the middle of the Arabia shield. The deep structure under the Eratosthenes seamount in the Mediterranean Sea is the source of the intensity and genesis of tectonic activity. Furthermore, the convergence region of two low-density anomaly zones (Africa-Anatolia) may be interpreted as a significant tectonic unit (Eratosthenes seamount) caused by the arrival of the relatively thick and buoyant Eratosthenes block to its present location south of Cyprus in Holocene time based on the density model interpretation beneath the Mediterranean Sea during the Late Cretaceous and early Tertiary period.
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| 40. |
- Kazemi, Mohsen, et al.
(författare)
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Development of antimicrobial gelatin-ulvan-beeswax composite films: Optimization of formulation using mixture design methodology
- 2023
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Ingår i: International Journal of Biological Macromolecules. - : Elsevier BV. - 0141-8130 .- 1879-0003. ; 231
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Tidskriftsartikel (refereegranskat)abstract
- A new generation of antimicrobial film was developed by incorporation of ulvan extracted from Ulva intestinalis into gelatin from common carp scale and its water sensitivity was reduced with addition of beeswax. Optimum composition of gelatin (0–100%w/w), ulvan (0–100%w/w) and beeswax (0–10%w/w) for achieving composite films with minimum water solubility (S) and water vapor permeability (WVP) and maximum tensile strength (TS), elongation at break point (EAB) and antibacterial effect on E. coli (EC) were investigated using mixture design methodology. Both pure gelatin and ulvan films and their composites had relatively good mechanical and optical properties. Addition of ulvan to gelatin produced composite films with good antibacterial properties but water resistance of all the films was weak. Addition of beeswax up to ∼5 % improved the water resistance and mechanical properties of the films without jeopardizing their antibacterial properties. The final optimum formulation with a desirability of 0.709 was achieved as 52.18 % of gelatin, 40.83 % of ulvan and 6.97 % of beeswax resulting in a minimum possible S (40 %) and WVP (1.86 10−10 g/ms Pa) and maximum possible TS (6.23 MPa) and EAB (89 %) with good EC (7.66 mm). Finally, good mechanical, thermal and microstructural properties of the optimum composite film was confirmed. Altogether, a combination of ulvan and beeswax can be a promising solution for development of gelatin films with both antimicrobial properties and lower water sensitivity.
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| 41. |
- Waldreus, Nana, et al.
(författare)
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Thirst in heart failure: a systematic literature review
- 2013
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Ingår i: European Journal of Heart Failure. - : Oxford University Press (OUP): Policy B. - 1388-9842 .- 1879-0844. ; 15:2, s. 141-149
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Forskningsöversikt (refereegranskat)abstract
- Although patients with heart failure (HF) may suffer from severe thirst, this has received little attention in scientific studies. A systematic literature review was conducted to identify and analyse data on thirst in HF. less thanbrgreater than less thanbrgreater thanPubmed, Cochrane, Cinahl, and Medline databases were searched for original studies on patients with HF with thirst as an outcome measure. Of 174 screened citations, nine articles were included, in which a total of 4375 HF patients had been studied. Four studies comprising 181 patients provided visual analogue scale (VAS) scores. Median thirst intensity ranged from 23 to 75 mm (VAS 0100 mm). One study showed 2 prevalence of thirst in a placebo group and another study showed that 46 of HF patients (n 25) experienced thirst distress. Thirst was described as annoying and as a cause of suffering. In most studies, the main results reflect a poor description of several dimensions of thirst. Factors that affected thirst were related to treatment, HF condition, demographics, and emotions. The consequences of thirst in HF were related to compliance, preoccupation with thirst, and a negative impact on quality of life. less thanbrgreater than less thanbrgreater thanThirst may be increased and experienced as distressing in patients with HF, but there is limited knowledge about the causative factors. More research is needed to study the effects of thirst and effective interventions in order to relieve troublesome thirst in HF patients.
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| 42. |
- Lesen, Eva, et al.
(författare)
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Impact of short periods with worsened or improved INR control on life expectancy and QALYs in patients with atrial fibrillation
- 2014
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Ingår i: THROMBOSIS RESEARCH. - : Elsevier BV. - 0049-3848 .- 1879-2472. ; 133:6, s. 1061-1067
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: Warfarin-treated patients with poor international normalized ratio (INR) control, measured with time in therapeutic range (TTR) or the standard deviation of transformed INR (SDTINR), have an increased risk for clinical events. To what extent only a short period with an altered INR control may influence outcomes remains unknown. This study assessed the impact of transient periods of worsened or improved INR control on life expectancy and quality-adjusted life years (QALYs) among warfarin-treated patients with atrial fibrillation (AF) using both metrics. Materials and methods: Warfarin-treated patients with AF, registered in the patient record system Journalia during years 1985-2000, were included. Information on all-cause mortality was collected from the Cause of Death Register. Hypothetical scenarios where patients were assumed to have a transiently altered INR control during 30 days were modeled statistically using hazard functions, and the impact on remaining life expectancy and QALYs was assessed. Results: When using SDTINR, a 70-year old man within the 20th best INR control percentile was estimated to lose 7.4 days of life or 0.0100 QALYs from a 30-day long worsened INR control to that of an average 70-year old male patient. Correspondingly, 4.0 days of life or 0.0059 QALYs would be gained if a 70-year old man within the 20th worst INR control percentile would have an average INR control during 30 days. The magnitudes were smaller when TTR was used to determine INR control. Conclusions: Even short periods of an altered INR control is expected to have impact on life expectancy and QALYs among patients with AF.
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