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- Duffy, J. E., et al.
(författare)
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Biodiversity mediates top-down control in eelgrass ecosystems: a global comparative-experimental approach
- 2015
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 18:7, s. 696-705
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Tidskriftsartikel (refereegranskat)abstract
- Nutrient pollution and reduced grazing each can stimulate algal blooms as shown by numerous experiments. But because experiments rarely incorporate natural variation in environmental factors and biodiversity, conditions determining the relative strength of bottom-up and top-down forcing remain unresolved. We factorially added nutrients and reduced grazing at 15 sites across the range of the marine foundation species eelgrass (Zostera marina) to quantify how top-down and bottom-up control interact with natural gradients in biodiversity and environmental forcing. Experiments confirmed modest top-down control of algae, whereas fertilisation had no general effect. Unexpectedly, grazer and algal biomass were better predicted by cross-site variation in grazer and eelgrass diversity than by global environmental gradients. Moreover, these large-scale patterns corresponded strikingly with prior small-scale experiments. Our results link global and local evidence that biodiversity and top-down control strongly influence functioning of threatened seagrass ecosystems, and suggest that biodiversity is comparably important to global change stressors.
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| 2. |
- Brandhorst, H., et al.
(författare)
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Quality of Isolated Pig Islets Is Improved Using Perfluorohexyloctane for Pancreas Storage in a Split Lobe Model
- 2013
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Ingår i: Cell Transplantation. - 0963-6897 .- 1555-3892. ; 22:8, s. 1477-1483
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Tidskriftsartikel (refereegranskat)abstract
- Pancreas transportation between donor center and islet production facility is frequently associated with prolonged ischemia impairing islet isolation and transplantation outcomes. It is foreseeable that shipment of pig pancreases from distant centralized biosecure breeding facilities to institutes that have a long-term experience in porcine islet isolation is essentially required in future clinical islet xenotransplantation. Previously, we demonstrated that perfluorohexyloctan (F6H8) is significantly more efficient to protect rat and human pancreata from ischemically induced damage compared to perfluorodecalin (PFD). To evaluate the effect of F6H8 on long-term stored pig pancreases in a prospective study, we utilized the split lobe model to minimize donor variability. Retrieved pancreases were dissected into the connecting and splenic lobe, intraductally flushed with UW solution and immersed alternately in either preoxygenated F6H8 or PFD for 8-10 h. Prior to pancreas digestion, the intrapancreatic pO(2) and the ratio of ATP-to-inorganic phosphate was compared utilizing P-31-NMR spectroscopy. Isolated islets were cultured for 2-3 days at 37 degrees C and subjected to quality assessment. Pancreatic lobes stored in preoxygenated F6H8 had a significantly higher intrapancreatic pO(2) compared to pancreata in oxygen-precharged PFD (10.11 +/- 3.87 vs. 1.64 +/- 1.13 mmHg, p < 0.05). This correlated with a higher ATP-to-inorganic phosphate ratio (0.30 +/- 0.04 vs. 0.14 +/- 0.01). No effect was observed concerning yield and purity of freshly isolated islets. Nevertheless, a significantly improved glucose-stimulated insulin response, increased viability and postculture survival (57.2 +/- 5.7 vs. 39.3 +/- 6.4%, p < 0.01) was measured in islets isolated from F6H8-preserved pancreata. The present data suggest that F6H8 does not increase islet yield but improves quality of pig islets isolated after prolonged cold ischemia.
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| 3. |
- Ruesink, JL., et al.
(författare)
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Form–function relationships in a marine foundation species depend on scale: a shoot to global perspective from a distributed ecological experiment
- 2018
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Ingår i: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 127:3, s. 364-374
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Tidskriftsartikel (refereegranskat)abstract
- Form–function relationships in plants underlie their ecosystem roles in supporting higher trophic levels through primary production, detrital pathways, and habitat provision. For widespread, phenotypically-variable plants, productivity may differ not only across abiotic conditions, but also from distinct morphological or demographic traits. A single foundation species, eelgrass Zostera marina, typically dominates north temperate seagrass meadows, which we studied across 14 sites spanning 32–61°N latitude and two ocean basins. Body size varied by nearly two orders of magnitude through this range, and was largest at mid-latitudes and in the Pacific Ocean. At the global scale, neither latitude, site-level environmental conditions, nor body size helped predict productivity (relative growth rate 1–2% day-1 at most sites), suggesting a remarkable capacity of Z. marina to achieve similar productivity in summer. Furthermore, among a suite of stressors applied within sites, only ambient leaf damage reduced productivity; grazer reduction and nutrient addition had no effect on eelgrass size or growth. Scale-dependence was evident in different allometric relationships within and across sites for productivity and for modules (leaf count) relative to size. Zostera marina provides a range of ecosystem functions related to both body size (habitat provision, water flow) and growth rates (food, carbon dynamics). Our observed decoupling of body size and maximum production suggests that geographic variation in these ecosystem functions may be independent, with a future need to resolve how local adaptation or plasticity of body size might actually enable more consistent peak productivity across disparate environmental conditions.
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