| 1. |
- Arroyo, Nina Larissa, et al.
(författare)
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Interactions between two closely related phytal harpacticoid copepods, asymmetric positive and negative effects
- 2007
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Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981 .- 1879-1697. ; 341:2, s. 219-227
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Tidskriftsartikel (refereegranskat)abstract
- Competition for food is generally thought to exert a strong evolutionary pressure, driving trophic niche separation, either by specialization and/or by widening the choice of potential food resources. Harpacticoid copepods are common inhabitants of phytal assemblages, where several closely related species of the so-called phytal dwelling families often co-occur. However, direct competition among phytal harpacticoids has been thought to be unlikely, due to the abundant and continuously available food supplies. We conducted a series of field and laboratory studies to assess the role of competition in the abundance distribution of two closely related harpacticoid species, Mesochra rapiens and M. aestuari. We found that the abundance of both species co-varied on several seaweed species in the northern Baltic Sea, during a 3-month period. Stable isotope ratios in the green alga Cladophora glomerata field samples indicated different resource utilization of the two species, both in fresh and deteriorated C. glomerata, and in drifting algae. We tested in the laboratory if resource utilization was different between the species in sympatry and allopatry. We used enriched stable carbon isotope ratios (C-13/C-12) of the diatom Phaeodactylum tricornutum to trace the uptake in both species. Results from these experiments showed a much higher assimilation by M. aestuari in sympatry with M. rapiens, while the latter species showed a higher assimilation in allopatry. Our results show that while there is no apparent competition for resources between these two species in the field, there seems to be an asymmetric reaction when in sympatry and provided one single resource in the laboratory. We suggest that M. rapiens may facilitate assimilation by M. acstuari and discuss the mechanisms by which this may take place.
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| 2. |
- Hanifpour, Fatemeh, et al.
(författare)
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Operando quantification of ammonia produced from computationally-derived transition metal nitride electro-catalysts
- 2022
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Ingår i: Journal of Catalysis. - : Elsevier. - 0021-9517 .- 1090-2694. ; 413, s. 956-967
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Tidskriftsartikel (refereegranskat)abstract
- Electrochemical reduction of dinitrogen to ammonia is investigated in a micro-reactor flow-cell using thin films of VN, CrN, NbN and ZrN. Chronoamperometry loops are used for ammonia production analysis. Operando ammonia quantification is accomplished in a flow injection analyzer. Results show the effect of presence/absence of N-2(g) within both the electrochemical characterization and ammonia production for ZrN. However, no ammonia is detected from studies on CrN. VN and NbN are inactivated upon reacting their N atoms of the surface top layer(s). Results obtained from ammonia measurements, electrochemical impedance spectroscopy analysis, surface stability checks, and surface characterization using X-ray reflectivity, reveal certain trends indicating catalytic behavior for ZrN. However, the concentration of produced ammonia is below the detection limit of the methods devised to analyze the samples from isotope labeling experiments. The onset of ammonia production on ZrN appears to be in close agreement with that predicted previously by computational studies.
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| 3. |
- Helgadottir, Anna, et al.
(författare)
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Genome-wide analysis yields new loci associating with aortic valve stenosis
- 2018
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 9:1
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Tidskriftsartikel (refereegranskat)abstract
- Aortic valve stenosis (AS) is the most common valvular heart disease, and valve replacement is the only definitive treatment. Here we report a large genome-wide association (GWA) study of 2,457 Icelandic AS cases and 349,342 controls with a follow-up in up to 4,850 cases and 451,731 controls of European ancestry. We identify two new AS loci, on chromosome 1p21 near PALMD (rs7543130; odds ratio (OR) = 1.20, P = 1.2 × 10-22) and on chromosome 2q22 in TEX41 (rs1830321; OR = 1.15, P = 1.8 × 10-13). Rs7543130 also associates with bicuspid aortic valve (BAV) (OR = 1.28, P = 6.6 × 10-10) and aortic root diameter (P = 1.30 × 10-8), and rs1830321 associates with BAV (OR = 1.12, P = 5.3 × 10-3) and coronary artery disease (OR = 1.05, P = 9.3 × 10-5). The results implicate both cardiac developmental abnormalities and atherosclerosis-like processes in the pathogenesis of AS. We show that several pathways are shared by CAD and AS. Causal analysis suggests that the shared risk factors of Lp(a) and non-high-density lipoprotein cholesterol contribute substantially to the frequent co-occurence of these diseases.
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| 4. |
- Malmgren, Linnea, et al.
(författare)
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The complexity of kidney disease and diagnosing it - Cystatin C, selective glomerular hypofiltration syndromes and proteome regulation.
- 2023
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Ingår i: Journal of Internal Medicine. - : John Wiley & Sons. - 0954-6820 .- 1365-2796. ; 293:3, s. 293-308
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Tidskriftsartikel (refereegranskat)abstract
- Estimation of kidney function is often part of daily clinical practice, mostly done by using the endogenous GFR-markers creatinine or cystatin C. A recommendation to use both markers in parallel in 2010 has resulted in new knowledge concerning the pathophysiology of kidney disorders by identification of a new set of kidney disorders, selective glomerular hypofiltration syndromes. These syndromes, connected to strong increases in mortality and morbidity, are characterised by a selective reduction in the glomerular filtration of 5-30 kDa molecules, such as cystatin C, compared to the filtration of small molecules < 1kDa dominating the glomerular filtrate e.g., water, urea, creatinine. At least two types of such disorders, shrunken or elongated pore syndrome, are possible according to the pore model for glomerular filtration. Selective glomerular hypofiltration syndromes are prevalent in investigated populations, and patients with these syndromes often display normal measured GFR or creatinine-based GFR-estimates. The syndromes are characterised by proteomic changes promoting the development of atherosclerosis, indicating antibodies and specific receptor-blocking substances as possible new treatment modalities. Presently, the KDIGO guidelines for diagnosing kidney disorders do not recommend cystatin C as a general marker of kidney function and will therefore not allow the identification of a considerable number of patients with selective glomerular hypofiltration syndromes. Furthermore, as cystatin C is uninfluenced by muscle mass, diet or variations in tubular secretion and cystatin C-based GFR-estimation equations do not require controversial race or sex terms, it is obvious that cystatin C should be a part of future KDIGO guidelines.
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| 5. |
- Messias, M. J, et al.
(författare)
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The Greenland Sea tracer experiment 1996–2002: Horizontal mixing and transport of Greenland Sea Intermediate Water
- 2008
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Ingår i: Progress In Oceanography. - : Elsevier BV. - 0079-6611. ; 78:1, s. 85-105
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Tidskriftsartikel (refereegranskat)abstract
- In summer 1996, a tracer release experiment using sulphur hexafluoride (SF6) was launched in the intermediate-depth waters of the central Greenland Sea (GS), to study the mixing and ventilation processes in the region and its role in the northern limb of the Atlantic overturning circulation. Here we describe the hydrographic context of the experiment, the methods adopted and the results from the monitoring of the horizontal tracer spread for the 1996–2002 period documented by 10 shipboard surveys. The tracer marked “Greenland Sea Arctic Intermediate Water” (GSAIW). This was redistributed in the gyre by variable winter convection penetrating only to mid-depths, reaching at most 1800 m depth during the strongest event observed in 2002. For the first 18 months, the tracer remained mainly in the Greenland Sea. Vigorous horizontal mixing within the Greenland Sea gyre and a tight circulation of the gyre interacting slowly with the other basins under strong topographic influences were identified. We use the tracer distributions to derive the horizontal shear at the scale of the Greenland Sea gyre, and rates of horizontal mixing at 10 and 300 km scales. Mixing rates at small scale are high, several times those observed at comparable depths at lower latitudes. Horizontal stirring at the sub-gyre scale is mediated by numerous and vigorous eddies. Evidence obtained during the tracer release suggests that these play an important role in mixing water masses to form the intermediate waters of the central Greenland Sea. By year two, the tracer had entered the surrounding current systems at intermediate depths and small concentrations were in proximity to the overflows into the North Atlantic. After 3 years, the tracer had spread over the Nordic Seas basins. Finally by year six, an intensive large survey provided an overall synoptic documentation of the spreading of the tagged GSAIW in the Nordic Seas. A circulation scheme of the tagged water originating from the centre of the GS is deduced from the horizontal spread of the tracer. We present this circulation and evaluate the transport budgets of the tracer between the GS and the surroundings basins. The overall residence time for the tagged GSAIW in the Greenland Sea was about 2.5 years. We infer an export of intermediate water of GSAIW from the GS of 1 to 1.85 Sv (1 Sv = 106 m3 s−1) for the period from September 1998 to June 2002 based on the evolution of the amount of tracer leaving the GS gyre. There is strong exchange between the Greenland Sea and Arctic Ocean via Fram Strait, but the contribution of the Greenland Sea to the Denmark Strait and Iceland Scotland overflows is modest, probably not exceeding 6% during the period under study.
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| 6. |
- Ndaro, Simon G. M., et al.
(författare)
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Small-Scale Variation in Major Meiofaunal Taxa and Sediment Chemistry in Tropical Sediments
- 1995
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Ingår i: Ambio. - 0044-7447 .- 1654-7209. ; 24:7/8, s. 470-474
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Tidskriftsartikel (refereegranskat)abstract
- Variations in sediment biochemistry and abundance of meiofauna were investigated in three tropical habitats: mangrove forest, intertidal lagoon, and subtidal reef area in eastern Africa. Both the biochemical components of the pore water and the meiofauna varied substantially over small distances in all three habitats. In the mangrove area, the color of the pore water was found to be positively correlated with the major meiofaunal taxa, especially the nematodes. In the coastal lagoon, polychaetes showed negative correlation with particulate organic matter while other groups showed no correlation with any of the chemical components analyzed. In the subtidal reef area no chemical components were found to correlate with the meiofauna. When data from the three habitats are taken together two clear associations emerge. First, grain size shows a highly significant relationship with both total fauna and nematode numbers. Second, there is clear association between the amount of particulate organic carbon and particulate organic nitrogen in the pore water.
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| 7. |
- Olafsson, Emil, et al.
(författare)
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Fauna of the green alga Cladophora glomerata in the Baltic Sea : density, diversity, and algal decomposition stage
- 2013
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Ingår i: Marine Biology. - : Springer Science and Business Media LLC. - 0025-3162 .- 1432-1793. ; 160:9, s. 2353-2362
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Tidskriftsartikel (refereegranskat)abstract
- The green alga Cladophora glomerata (L.) is a common macrophyte in the northern Baltic Sea, where it forms drifting mats during summer. We studied the effect of its stage of decomposition on the density, diversity, and resource usage of associated meio- and macrofauna. We hypothesised that mobile species would show small variation in food preferences among decomposition stages, while high variation was expected in stationary species, as reflected in their stable isotope signatures. The assemblage structure of the fauna differed between the 3 studied algal degradation stages, Green (attached, healthy), Degraded (attached, but starting to decay), and Drift (detached, decaying). C/N ratios were highest in green algae and decreased in decaying algal stages. Variation in stable isotope ratios of stationary and mobile species supported our resource use hypothesis. The decomposition stage of C. glomerata significantly affected the carbon and nitrogen stable isotope ratios of both the alga and its main grazer species. Higher invertebrate diversity in the more decaying stages was probably facilitated by decomposer microbes adding resource types and by the proximity of the detached algal mats to the sediment.
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| 8. |
- Olsen, Are, 1972, et al.
(författare)
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Overview of the Nordic Seas CARINA data and salinity measurements
- 2009
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Ingår i: Earth System Science Data Discussions. - 1866-3591. ; 2, s. 1-25
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Tidskriftsartikel (refereegranskat)abstract
- Water column data of carbon and carbon relevant hydrographic and hydrochemical parameters from 188 previously non-publicly available cruises in the Arctic, Atlantic, and Southern Ocean have been retrieved and merged into a new database: CARINA (CARbon IN the Atlantic). The data have been subject to rigorous quality control (QC) in order to ensure highest possible quality and consistency. The data for most of the parameters included were examined in order to quantify systematic biases in the reported values, i.e. secondary quality control. Significant biases have been corrected for in the data products, i.e. the three merged files with measured, calculated and interpolated values for each of the three CARINA regions; the Arctic Mediterranean Seas (AMS), the Atlantic (ATL) and the Southern Ocean (SO). With the adjustments the CARINA database is consistent both internally as well as with GLODAP (Key et al., 2004) and is suitable for accurate assessments of, for example, oceanic carbon inventories and uptake rates and for model validation. The Arctic Mediterranean Seas includes the Arctic Ocean and the Nordic Seas, and the quality control was carried out separately in these two areas. This contribution provides an overview of the CARINA data from the Nordic Seas and summarises the findings of the QC of the salinity data. One cruise had salinity data that were of questionable quality, and these have been removed from the data product. An evaluation of the consistency of the quality controlled salinity data suggests that they are consistent to at least 0.05.
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| 9. |
- Ullberg, Jörgen, 1960-
(författare)
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Dispersal in free-living, marine, benthic nematodes : passive or active processes?
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Meiofauna, and especially marine nematodes are common in sediments around the world. Despite very wide ranging distributions in many nematode species, little is presently known about their dispersal mechanisms shaping these patterns. Rafting, and perhaps ballast water transport has been suggested as viable means for nematode long-range transport. On a much smaller scale other processes have been suggested for their dispersal. They generally include some form of passive suspension into the water column and later on a passive, haphazard settling back towards the bottom.Small-scale phenomena in nematode dispersal were studied by conducting a series of studies at Askö field station, Trosa Archipelago, Baltic proper. Studied aspects were one case of macrofaunal influence on nematode dispersal rate, using an amphipod, Monoporeia affinis as disturbing agent, and three different studies on mechanisms related to settling. The experiments were conducted both in laboratory and field settings.The amphipod Monoporeia affinis did not exert any influence on the dispersal rate in the nematodes. The nematode dispersal was only an effect of time, in the aspect that the more time that past, the more nematodes dispersed from their place of origin. The settling experiments revealed that nematodes do have an active component in their settling behaviour, as they were able to exert influence on the spot where they were to settle. They were able to choose settling spot in response to the food quality of the sediment. It also became evident that contrary to common belief, nematodes are able to extend their presence in the water column far beyond the times that would be predicted considering settling velocities and hydrodynamic conditions alone.
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