| 1. |
- Bodvik, Rasmus, et al.
(författare)
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Aggregation and network formation of aqueous methylcellulose and hydroxypropylmethylcellulose solutions.
- 2010
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Ingår i: Colloids and Surfaces A. - : Elsevier. - 0927-7757 .- 1873-4359. ; 354:1-3, s. 162-171
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Tidskriftsartikel (refereegranskat)abstract
- Solution properties of methylcellulose (MC) and hydroxypropylmethylcellulose (HPMC) have been investigated as a function of temperature and concentration using a broad range of experimental techniques. Novelties include the extensive comparison between MC and HPMC solutions as well as the combination of techniques, and the use of Cryo transmission electron microscopy (Cryo-TEM). The correlation between rheology and light scattering results clearly demonstrates the relation between viscosity change and aggregation. Cryo-TEM images show the network structures formed. Viscosity measurements show that for both MC and HPMC solutions sudden changes in viscosity occur as the temperature is increased. The onset temperature for these changes depends on polymer concentration and heating rate. For both MC and HPMC solutions the viscosity on cooling is very different compared to on heating, demonstrating the slow equilibration time. The viscosity changes in MC and HPMC solutions are dramatically different; for MC solutions the viscosity increases by several orders of magnitude when a critical temperature is reached, whereas for HPMC solutions the viscosity decreases abruptly at a given temperature, followed by an increase upon further heating. Light and (SAXS) small-angle X-ray scattering shows that the increase in viscosity, for MC as well as for HPMC solutions, is due to extensive aggregation of the polymers. Light scattering also provides information on aggregation kinetics. The SAXS measurements allow us to correlate aggregation hysteresis to the viscosity hysteresis, as well as to extract some structural information. Cryo-TEM images give novel information that a fibrillar network is formed in MC solutions, and the strong viscosity increase occurs when this network spans the whole solution volume. For HPMC solutions the behaviour is more complex. The decrease in viscosity can be related to the formation of compact objects, and the subsequent increase to formation of fibrillar structures, which are more linear and less entangled than for MC.
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| 2. |
- Ljunggren, Lars, et al.
(författare)
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Recruitment failure of coastal predatory fish in the Baltic Sea coincident with an offshore ecosystem regime shift
- 2010
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Ingår i: ICES Journal of Marine Science. - : Oxford University Press (OUP). - 1054-3139 .- 1095-9289. ; 67:8, s. 1587-1595
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Tidskriftsartikel (refereegranskat)abstract
- The dominant coastal predatory fish in the southwestern Baltic Sea, perch and pike, have decreased markedly in abundance during the past decade. An investigation into their recruitment at 135 coastal sites showed that both species suffered from recruitment failures, mainly in open coastal areas. A detailed study of 15 sites showed that areas with recruitment problems were also notable for mortality of early-stage larvae at the onset of exogenous food-intake. At those sites, zooplankton abundance predicted 83 and 34% of the variation in young of the year perch and pike, respectively, suggesting that the declines were caused by recruitment failure attributable to zooplankton food limitation. Incidences of recruitment failure match in time an offshore trophic cascade that generated massive increases in planktivorous sprat and decreases in zooplankton biomass in the early 1990s. Therefore, sprat biomass explained 53% of the variation in perch recruitment from 1994 to 2007 at an open coastal site, where three-spined stickleback also increased exponentially after 2002. The results indicate that the dramatic change in the offshore ecosystem may have propagated to the coast causing declines of the dominating coastal predators perch and pike followed by an increase in the abundance of small-bodied fish.
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| 3. |
- Snickars, Martin, et al.
(författare)
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Habitat selectivity of substrate-spawning fish: modelling requirements for the Eurasian perch Perca fluviatilis
- 2010
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Ingår i: Marine Ecology Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 398, s. 235-243
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Tidskriftsartikel (refereegranskat)abstract
- Substrate spawning fish are believed to be selective in their choice of spawning habitat,yet few studies have shown the relative importance of different characteristics in terms of habitatquality. We used an extensive and detailed dataset to identify the factors that govern both large-scale(1 000 to 100 000 m) and local-scale (10 to 100 m) selection by a substrate-spawning fish, the Eurasian perchPerca fluviatilis L. Distribution of spawning habitat was strongly dependent on habitat characteristicsdefined by substrate, wave exposure, temperature and depth. The most important predictor was thetype of spawning substrate, which generally consisted of different types of vegetation. Substratesproviding rigidity and structural complexity were preferred, despite abundant presence of other substratetypes. Shallow depth and sheltered areas were also selected habitat characteristics. Theresponse to temperature was scale-dependent, with a stronger selection expressed at the local scale.The specific selectivity suggests that spawning patterns can be successfully modelled with sufficientdetail using only a few fundamental environmental variables. Wave exposure and depth are readilyavailable for large-scale spatial predictions, while temperature and substrate require further developmentin most coastal areas. The high specificity of the characteristics determining habitat qualitysuggests that it should be possible to apply this modelling approach for identification and conservationof spawning habitats of Eurasian perch and other substrate-spawning fishes in coastal waters.
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| 4. |
- Sundblad, Göran, et al.
(författare)
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Ecological coherence of Marine Protected Area networks : A spatial assessment using species distribution models
- 2011
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Ingår i: Journal of Applied Ecology. - : Wiley. - 0021-8901 .- 1365-2664. ; 48:1, s. 112-120
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Tidskriftsartikel (refereegranskat)abstract
- The juvenile stages of fish are often dependent on specific habitat types for their survival. Protecting these habitats may be crucial for maintaining strong adult stocks. The Natura 2000 network of the European Union offers protection of marine habitats that are essential for the recruitment of many fish species. By protecting these critical habitats the network may be important for maintaining the stocks of these fish species. 2.We present a spatially explicit, GIS-based, assessment of two important components of the ecological coherence of Marine Protected Area (MPA) networks: representativity and connectivity. Representativity can be measured as the proportion of each conservation feature that is protected, whereas connectivity assesses the spatial configuration of the network. We apply these analyses to study the ecological coherence of the Natura 2000 network in a 30 000-km2 archipelago in the Baltic Sea, with respect to a coastal fish assemblage and associated habitats. The analyses are based on fish distribution maps that have been constructed by statistically relating life stage specific occurrence to environmental variables, and thereafter making spatial predictions based on maps of the environmental variables. 3.The map-based analyses show that both the representativity and the connectivity of the network are poor with respect to the studied fish species. In total, 3.5% (11 km2) of the assemblage recruitment habitat was protected and 48% of the potentially connected habitats were included in the MPA network. 4.The assessment explicitly identified geographical areas, visually communicated using maps, where the network should be improved to ensure ecological coherence. 5.Synthesis and applications.Many MPA networks around the world, such as the Natura 2000 network in Europe, have recently come into effect. Establishment of the networks has often been governed by opportunity rather than by strict ecological analyses, primarily because distribution maps of species and habitats have been unavailable. Map-based assessments of the strengths and weaknesses of evolving MPA networks, such as the one presented here, are needed in adaptive management. They can provide an efficient tool for visualising and communicating the results to stakeholders and policy makers in the process of working towards ecological coherence.
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| 5. |
- Sundblad, Göran
(författare)
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Spatial Modelling of Coastal Fish – Methods and Applications
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Environmental factors influence species and habitats on multiple scales creating a mosaic of distribution patterns. Studying factors shaping these patterns are central to our understanding of population dynamics and ultimately ecosystem functioning. Information on the distribution of resources and conservation values are also highly needed in marine management as coastal areas are increasingly influenced by human activities. In this thesis, large-scale field data is used to explore how strong environmental gradients found on multiple scales in the coastal areas of the Baltic Sea influence fish habitats. The underlying concepts are based in the field of species distribution modelling, whereby habitat maps can be produced using environmental layers in a geographic information system. Distribution modelling is further used to address both ecological and applied questions by examining effects of habitat limitation on fish population sizes and to evaluate management actions aimed at habitat conservation. I show that specific habitat requirements for fish species of both freshwater and marine origin can be described using environmental variables and that species-environment relationships can be used to predict the distribution of early life-stages of fish in the Baltic Sea archipelagos. Further, predicted habitat availability of a specific life-stage was directly related to adult population size of Eurasian perch Perca fluviatilis, signifying that the abundance of large predatory fish can be limited by specific recruitment habitats. Lastly, by predicting the distribution of an assemblage of coastal fish species and their associated habitats, an assessment of a network of marine protected areas was performed. Results revealed large gaps in the current network and identified areas suitable for future protection. By demonstrating how current habitat protection can be improved by including critical habitats for coastal fish population sizes this thesis points to the benefits of integrating nature conservation and fisheries management. Based on these findings I conclude that species distribution modelling provides a suitable analytical framework for assessing the habitat requirements of organisms. An increased understanding of habitat-population relationships and an ability to accurately map ecologically important features will be of great value for an ecosystem-based marine management.
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