| 1. |
- Boras, Julia, et al.
(författare)
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Effect of viruses and protists on bacteria in eddies of the Canary Current region (subtropical Northeast Atlantic).
- 2010
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Ingår i: Limnology and Oceanography. - 0024-3590 .- 1939-5590. ; 55:2, s. 885-898
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Tidskriftsartikel (refereegranskat)abstract
- The effect of oceanic eddies on microbial processes, with emphasis on bacterial losses due to protists and phages, was examined in the Canary Current region (subtropical northeast Atlantic) through the water column (down to 1000 m) during August 2006. Sampling stations were located in cyclonic and anticyclonic eddies, as well as in regions situated outside the influence of the eddy field (far-field stations). In the euphotic zone, in cyclonic eddies losses of bacteria due to viruses and protists were from 25.6% to 69.8%, and from not detected to 46.8% of bacterial production (BP) d(-1), respectively. In anticyclonic eddies, these values ranged from 20.6% to 90.2% of BP d(-1) for viruses, and from 8.0% to 79.4% of BP d(-1) for protists. At far-field stations, losses of bacteria ranged from 48.7% to 66.9% for viruses, and from not detected to 44.8% for protists. In addition, covering all stations and depths (from the epipelagic to the bathypelagic layer), bacterial losses due to viruses were significantly higher than losses by protists, and did not differ significantly among depths except for the stations situated in anticyclonic eddies, where they were significantly higher in the epipelagic layer. Lysogenic infection was more frequent at anticyclonic stations, where the highest pressure of protists on bacteria was observed. Because of the importance of viral activity, we suggest that lysis products from bacteria may be a source of regenerated nutrients in the surface of the oligotrophic ocean, in addition to the input of nutrients upwelled by eddies.
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| 2. |
- Duarte, Carlos M., et al.
(författare)
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Tipping Elements in the Arctic Marine Ecosystem
- 2012
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Ingår i: Ambio: a Journal of Human Environment. - : Springer Science and Business Media LLC. - 0044-7447. ; 41:1, s. 44-55
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Tidskriftsartikel (refereegranskat)abstract
- The Arctic marine ecosystem contains multiple elements that present alternative states. The most obvious of which is an Arctic Ocean largely covered by an ice sheet in summer versus one largely devoid of such cover. Ecosystems under pressure typically shift between such alternative states in an abrupt, rather than smooth manner, with the level of forcing required for shifting this status termed threshold or tipping point. Loss of Arctic ice due to anthropogenic climate change is accelerating, with the extent of Arctic sea ice displaying increased variance at present, a leading indicator of the proximity of a possible tipping point. Reduced ice extent is expected, in turn, to trigger a number of additional tipping elements, physical, chemical, and biological, in motion, with potentially large impacts on the Arctic marine ecosystem.
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| 3. |
- Kritzberg, Emma, et al.
(författare)
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Temperature and phosphorus regulating carbon flux through bacteria in a coastal marine system
- 2010
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Ingår i: Aquatic Microbial Ecology. - : Inter-Research Science Center. - 0948-3055 .- 1616-1564. ; 58:2, s. 141-151
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to explore the variation and regulation of bacterial carbon processing at a coastal oligotrophic site of the Island of Majorca in the Mediterranean Sea. In situ bacterial production (BP), respiration (BR), growth efficiency, and carbon demand in relation to environmental parameters were studied over an annual cycle. In addition, the response of bacterial carbon processing to an experimental resource (phosphate) and temperature manipulations was tested. While concentrations of dissolved organic carbon (DOC) and phosphorus were fairly stable over the year, BP and BR varied 65-fold and 79-fold, respectively. Addition of phosphate stimulated both BP and BR during most of the year, suggesting that phosphorus limitation keeps a tight rein on bacterial DOC utilization. Both BP and BR responded positively to a 2 degrees C experimental increase, but at higher temperature increases BP and BR leveled off or decreased. In situ BP and BR were positively related to temperature, suggesting that elevated water temperature would yield increased BP and BR. BR responded more strongly to temperature than BP, suggesting that increased temperature may result in a decrease in bacterial growth efficiency.
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| 4. |
- Calleja, Maria Ll., et al.
(författare)
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Prevalence of strong vertical CO2 and O-2 variability in the top meters of the ocean
- 2013
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Ingår i: Global Biogeochemical Cycles. - : American Geophysical Union (AGU). - 0886-6236. ; 27:3, s. 941-949
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Tidskriftsartikel (refereegranskat)abstract
- The gradient in the partial pressure of carbon dioxide (pCO(2)) across the air-sea boundary layer is the main driving force for the air-sea CO2 flux. Global data bases for surface seawater pCO(2) are actually based on pCO(2) measurements from several meters below the sea surface, assuming a homogeneous distribution between the diffusive boundary layer and the upper top meters of the ocean. Compiling vertical profiles of pCO(2), temperature, and dissolved oxygen in the upper 5-8 m of the ocean from different biogeographical areas, we detected a mean difference between the boundary layer and 5 m pCO(2) of 131 mu atm. Temperature gradients accounted for only 11% of this pCO(2) gradient in the top meters of the ocean; thus, pointing to a heterogeneous biological activity underneath the air-sea boundary layer as the main factor controlling the top meters pCO(2) variability. Observations of pCO(2) just beneath the air-sea boundary layer should be further investigated in order to estimate possible biases in calculating global air-sea CO2 fluxes.
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| 5. |
- Duell, Eric J, et al.
(författare)
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Vitamin C transporter gene (SLC23A1 and SLC23A2) polymorphisms, plasma vitamin C levels, and gastric cancer risk in the EPIC cohort
- 2013
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Ingår i: Genes & Nutrition. - : Springer Berlin/Heidelberg. - 1555-8932 .- 1865-3499. ; 8:6, s. 549-560
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Tidskriftsartikel (refereegranskat)abstract
- Vitamin C is known to protect mucosal tissues from oxidative stress and inhibit nitrosamine formation in the stomach. High consumption of fruits, particularly citrus, and higher circulating vitamin C concentrations may be inversely associated with gastric cancer (GC) risk. We investigated 20 polymorphisms in vitamin C transporter genes SCL23A1 and SCL23A2 and GC risk in 365 cases and 1,284 controls nested within the European Prospective Investigation into Cancer and Nutrition cohort. We also evaluated the association between these polymorphisms and baseline plasma vitamin C levels in a subset of participants. Four SNPs were predictors of plasma vitamin C levels (SLC23A1 rs11950646 and rs33972313; SLC23A2 rs6053005 and rs6133175) in multivariable linear regression models. One SNP (SLC23A2 rs6116569) was associated with GC risk, in particular non-cardia GC (OR = 1.63, 95 % CI = 1.11-2.39, based on 178 non-cardia cases), but this association was attenuated when plasma vitamin C was included in the logistic regression model. Haplotype analysis of SLC23A1 yielded no associations with GC. In SLC23A2, one haplotype was associated with both overall and non-cardia GC, another haplotype was associated with GC overall, and a third was associated with intestinal-type GC. Common variants in SLC23A1 and SLC23A2 may influence plasma vitamin C concentration independent of dietary intake, and variation in SLC23A2 may influence GC risk. Additional prospective studies in large populations and consortia are recommended. Investigation of variation in vitamin C transporter genes may shed light on the preventative properties of vitamin C in gastric carcinogenesis.
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| 6. |
- Espinosa-Parrilla, Yolanda, et al.
(författare)
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Genetic association of gastric cancer with miRNA clusters including the cancer-related genes MIR29, MIR25, MIR93 and MIR106: Results from the EPIC-EURGAST study
- 2014
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Ingår i: International Journal of Cancer. - : Wiley. - 0020-7136 .- 1097-0215. ; 135:9, s. 2065-2076
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Tidskriftsartikel (refereegranskat)abstract
- MicroRNAs (miRNAs) are post-transcriptional gene regulators involved in a wide range of biological processes including tumorigenesis. Deregulation of miRNA pathways has been associated with cancer but the contribution of their genetic variability to this disorder is poorly known. We analyzed the genetic association of gastric cancer (GC) and its anatomical and histological subtypes, with 133 single-nucleotide polymorphisms (SNPs) tagging 15 isolated miRNAs and 24 miRNA clusters potentially involved in cancer, in 365 GC cases and 1,284 matched controls within the European Prospective Investigation into Cancer and Nutrition cohort. Various SNPs were associated with GC under the log-additive model. Furthermore, several of these miRNAs passed the gene-based permutation test when analyzed according to GC subtypes: three tagSNPs of the miR-29a/miR-29b-1 cluster were associated with diffuse subtype (minimum p-value=1.7 x 10(-4); odds ratio, OR=1.72; 95% confidence interval, CI=1.30-2.28), two tagSNPs of the miR-25/miR-93/miR-106b cluster were associated with cardia GC (minimum p-value=5.38 x 10(-3); OR=0.56, 95% CI=0.37-0.86) and one tagSNP of the miR-363/miR-92a-2/miR-19b-2/miR-20b/miR-18b/miR-106a cluster was associated with noncardia GC (minimum p-value=5.40 x 10(-3); OR=1.41, 95% CI=1.12-1.78). Some functionally validated target genes of these miRNAs are implicated in cancer-related processes such as methylation (DNMT3A, DNMT3B), cell cycle (E2F1, CDKN1A, CDKN1C), apoptosis (BCL2L11, MCL1), angiogenesis (VEGFA) and progression (PIK3R1, MYCN). Furthermore, we identified genetic interactions between variants tagging these miRNAs and variants in their validated target genes. Deregulation of the expression of these miRNAs in GC also supports our findings, altogether suggesting for the fist time that genetic variation in MIR29, MIR25, MIR93 and MIR106b may have a critical role in genetic susceptibility to GC and could contribute to the molecular mechanisms of gastric carcinogenesis.
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| 7. |
- Kritzberg, Emma, et al.
(författare)
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Changes in Arctic marine bacterial carbon metabolism in response to increasing temperature
- 2010
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Ingår i: Polar Biology. - : Springer Science and Business Media LLC. - 1432-2056 .- 0722-4060. ; 33:12, s. 1673-1682
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Tidskriftsartikel (refereegranskat)abstract
- Arctic areas of deep-water convection have a large potential for export of organic carbon from surface waters into the deep sea and, therefore, are an important part of the global carbon cycle. As the Arctic is reportedly heating up faster than any other part of the planet, temperature-driven changes in the biogeochemical cycling in these areas can be very significant. Here, we study the regulation of bacterial carbon metabolism, which process vast amounts of organic carbon, by temperature and the availability of resources. The response of bacterial production and respiration of natural bacterial assemblages from the Fram Strait was studied by experimental manipulations of temperature and resources in combination. Both bacterial production and respiration were enhanced by temperature so that the total bacterial carbon demand increased sixfold following a temperature increase of 6A degrees C. Respiration responded more strongly than production so that bacterial growth efficiency decreased with increasing temperature. Although neither production nor respiration was limited by resource availability under in situ conditions, the response to temperature was higher in resource-amended treatments, indicative of a substrate-temperature interaction regulating both components of bacterial metabolism. In conclusion, the results show that warming can result in a substantial increase of the carbon flow through bacteria and that most of the carbon consumed would be released as CO2. Moreover, the results suggest that both temperature and availability of resources need to be considered to accurately be able to predict changes in bacterial carbon metabolism in response to climate change.
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| 8. |
- Mcleod, Elizabeth, et al.
(författare)
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A blueprint for blue carbon : toward an improved understanding of the role of vegetated coastal habitats in sequestering CO(2)
- 2011
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Ingår i: Frontiers in Ecology and the Environment. - : Wiley. - 1540-9295 .- 1540-9309. ; 9:10, s. 552-560
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Forskningsöversikt (refereegranskat)abstract
- Recent research has highlighted the valuable role that coastal and marine ecosystems play in sequestering carbon dioxide (CO(2)). The carbon (C) sequestered in vegetated coastal ecosystems, specifically mangrove forests, seagrass beds, and salt marshes, has been termed blue carbon. Although their global area is one to two orders of magnitude smaller than that of terrestrial forests, the contribution of vegetated coastal habitats per unit area to long-term C sequestration is much greater, in part because of their efficiency in trapping suspended matter and associated organic C during tidal inundation. Despite the value of mangrove forests, seagrass beds, and salt marshes in sequestering C, and the other goods and services they provide, these systems are being lost at critical rates and action is urgently needed to prevent further degradation and loss. Recognition of the C sequestration value of vegetated coastal ecosystems provides a strong argument for their protection and restoration; however, it is necessary to improve scientific understanding of the underlying mechanisms that control C sequestration in these ecosystems. Here, we identify key areas of uncertainty and specific actions needed to address them.
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| 9. |
- Vaquer-Sunyer, Raquel, et al.
(författare)
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Experimental Evaluation of the Response of Coastal Mediterranean Planktonic and Benthic Metabolism to Warming
- 2013
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Ingår i: Estuaries and Coasts. - : Springer Science and Business Media LLC. - 1559-2731 .- 1559-2723. ; 36:4, s. 697-707
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Tidskriftsartikel (refereegranskat)abstract
- The Mediterranean Sea has been identified as one of the hotspots for climate change. Intense warming in the Mediterranean Sea may have strong implications for biological activity and ecosystem functioning. To elucidate the effects of warming on planktonic and benthic metabolism, we performed experiments under different increasing temperature regimes, ranging from three to six different temperatures. The lowest range of temperatures assessed was of 2.6 A degrees C and the maximum was 7.5 A degrees C. Our results suggest that a 6 A degrees C warming of the Mediterranean waters may yield a mean increment in planktonic respiration rates of coastal communities of 24 %, higher than the mean increase expected for planktonic gross primary production (9 %). These results confirm earlier theories, and agree with previous experiments, of a higher increase in respiration rates than in primary production with warming, with the subsequent consequences for the carbon cycle, resulting in a negative feedback to climate warming, as ocean communities will capture less CO2.
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| 10. |
- Vaquer-Sunyer, Raquel, et al.
(författare)
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Temperature Dependence of Oxygen Dynamics and Community Metabolism in a Shallow Mediterranean Macroalgal Meadow (Caulerpa prolifera)
- 2012
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Ingår i: Estuaries and Coasts. - : Springer Science and Business Media LLC. - 1559-2731 .- 1559-2723. ; 35:5, s. 1182-1192
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Tidskriftsartikel (refereegranskat)abstract
- Hypoxia is emerging as a major threat to marine coastal biota. Predicting its occurrence and elucidating the driving factors are essential to set successful management targets to avoid its occurrence. This study aims to elucidate the effects of warming on the likelihood of hypoxia. High-frequency dissolved oxygen measurements have been used to estimate gross primary production (GPP), net ecosystem production (NEP) and community respiration (CR) in a shallow macroalgae (Caulerpa prolifera) ecosystem in a highly human-influenced closed Mediterranean bay. Daily averaged GPP and CR ranged from 0 to 1,240.9 and 51.4 to 1,297.3 mmol O-2 m(-2) day(-1), respectively. The higher GPP and CR were calculated for the same day, when daily averaged water temperature was 28.3 A degrees C, and resulted in a negative NEP of -56.4 mmol O-2 m(-2) day(-1). The ecosystem was net heterotrophic during the studied period, probably subsidized by allochthonous organic inputs from ground waters and from the surrounding town and boating activity. Oxygen dynamics and metabolic rates strongly depend on water temperature, with lower oxygen content at higher temperatures. The probability of hypoxic conditions increased at a rate of 0.39 % A degrees C-1 (+/- 0.14 % A degrees C-1). Global warming will increase the likelihood of hypoxia in the bay studied, as well as in other semi-enclosed bays.
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