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. |
- 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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3. |
- 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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4. |
- 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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5. |
- 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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6. |
- 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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7. |
- 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 ($10,000 μatm). In trial 1, there was evidence for significantly reduced larval survival (at mean pCO2 levelsZ4730 μatm) and growth (at mean pCO2 levels Z 2108 μatm), while egg hatch time was increased at extreme pCO2 levelsZ10,000 μatm (nintermediate levels were not tested). In trial 2, egg hatch times were increased at mean pCO2 levelsZ1573 μatm, but growth was only impacted at higher pCO2 (Z8800 μatm) and there was no relationship with survival. Unstable ambient conditions during trial 2 are likely to have contributed to the difference in results between trials. Despite the technical challenges with these experiments, there is a need for future empirical work which can in turn support modeling-based approaches to assess how OA will affect the ecologically and economically important tropical tuna resources.
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8. |
- Burd, Adrian B., et al.
(författare)
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Assessing the Apparent Imbalance Between Geochemical and Biochemical Indicators of Meso- and Bathypelagic Biological Activity: What the @$#! 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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9. |
- 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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10. |
- 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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11. |
- 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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12. |
- 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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13. |
- 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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14. |
- Engqvist, A, et al.
(författare)
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Archipelago strait exchange processes - an overview
- 2004
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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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15. |
- 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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16. |
- 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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17. |
- 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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18. |
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19. |
- 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
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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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20. |
- 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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21. |
- 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
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Ingår i: Deep-sea research. Part II, Topical studies in oceanography. - : Elsevier BV. - 0967-0645 .- 1879-0100. ; 51, s. 2569-2582
-
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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22. |
- 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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23. |
- 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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24. |
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25. |
- 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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