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| 2. |
- Rosén, Tomas, 1985-, et al.
(författare)
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Cross-Sections of Nanocellulose from Wood Analyzed by Quantized Polydispersity of Elementary Microfibrils
- 2020
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Ingår i: ACS Nano. - : American Chemical Society. - 1936-0851 .- 1936-086X. ; 14:12, s. 16743-16754
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Tidskriftsartikel (refereegranskat)abstract
- Bio-based nanocellulose has been shown to possess impressive mechanical properties and simplicity for chemical modifications. The chemical properties are largely influenced by the surface area and functionality of the nanoscale materials. However, finding the typical cross-sections of nanocellulose, such as cellulose nanofibers (CNFs), has been a long-standing puzzle, where subtle changes in extraction methods seem to yield different shapes and dimensions. Here, we extracted CNFs from wood with two different oxidation methods and variations in degree of oxidation and high-pressure homogenization. The cross-sections of CNFs were characterized by small-angle X-ray scattering and wide-angle X-ray diffraction in dispersed and freeze-dried states, respectively, where the results were analyzed by assuming that the cross-sectional distribution was quantized with an 18-chain elementary microfibril, the building block of the cell wall. We find that the results agree well with a pseudosquare unit having a size of about 2.4 nm regardless of sample, while the aggregate level strongly depends on the extraction conditions. Furthermore, we find that aggregates have a preferred cohesion of phase boundaries parallel to the (110)-plane of the cellulose fibril, leading to a ribbon shape on average.
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| 3. |
- Jönsson, K. Ingemar, et al.
(författare)
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Sexual patterns of prebreeding energy reserves in the common frog Rana temporaria along a latitudinal gradient
- 2009
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Ingår i: Ecography. - : Wiley. - 0906-7590 .- 1600-0587. ; 32:5, s. 831-839
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Tidskriftsartikel (refereegranskat)abstract
- The ability to store energy is an important life history trait for organisms facing long periods without energy income, and in particular for capital breeders such as temperate zone amphibians, which rely on stored energy during reproduction. However, large scale comparative studies of energy stores in populations with different environmental constraints on energy allocation are scarce. We investigated energy storage patterns in spring (after hibernation and before reproduction) in eight common frog Rana temporaria populations exposed to different environmental conditions along a 1600 km latitudinal gradient across Scandinavia (range of annual activity period is 3-7 months). Analyses of lean body weight (eviscerated body mass), weight of fat bodies, liver weight, and liver fat content, showed that 1) post-hibernation/pre-breeding energy stores increased with increasing latitude in both sexes, 2) males generally had larger energy reserves than females and 3) the difference in energy stores between sexes decreased towards the north. Larger energy reserves towards the north can serve as a buffer against less predictable and/or less benign weather conditions during the short activity period, and may also represent a risk-averse tactic connected with a more pronounced iteroparous life history. In females, the continuous and overlapping vitellogenic activity in the north may also demand more reserves in early spring. The general sexual difference could be a consequence of the fact that, at the time of our sampling, females had already invested their energy into reproduction in the given year (i.e. their eggs were already ovulated), while the males' main reproductive activities (e.g. calling, mate searching, sexual competition) occurred later in the season.
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| 7. |
- Jönsson, K. Ingemar, 1959-, et al.
(författare)
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Sexual patterns of prebreeding energy reserves in the common frog Rana temporaria along a latitudinal gradient
- 2009
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Ingår i: Ecography. - : Wiley-Blackwell. - 0906-7590 .- 1600-0587. ; 32:5, s. 831-839
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Tidskriftsartikel (refereegranskat)abstract
- The ability to store energy is an important life history trait for organisms facing long periods without energy income, and in particular for capital breeders such as temperate zone amphibians, which rely on stored energy during reproduction. However, large scale comparative studies of energy stores in populations with different environmental constraints on energy allocation are scarce. We investigated energy storage patterns in spring (after hibernation and before reproduction) in eight common frog (Rana temporaria) populations exposed to different environmental conditions along a 1600 km latitudinal gradient across Scandinavia (range of annual activity period 3-7 months). Analyses of lean body weight (eviscerated body mass), weight of fat bodies, liver weight, and liver fat content, showed that (i) post-hibernation/pre-breeding energy stores increased with increasing latitude in both sexes, (ii) males generally had larger energy reserves than females and (iii) the difference in energy stores between sexes decreased towards the north. Larger energy reserves towards the north can serve as a buffer against less predictable and/or less benign weather conditions during the short activity period, and may also represent a risk-averse tactic connected with a more pronounced iteroparous life history. In females, the continuous and overlapping vitellogenic activity in the north may also demand more reserves in early spring. The general sexual difference could be a consequence of the fact that, at the time of our sampling, females had already invested their energy into reproduction in the given year (i.e. their eggs were already ovulated), while the males' main reproductive activities (e.g. calling, mate searching, sexual competition) occurred later in the season.
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| 8. |
- Lundstedt-Enkel, Katrin, 1959-
(författare)
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QSBMR Quantitative Structure Biomagnification Relationships : Studies Regarding Persistent Environmental Pollutants in the Baltic Sea Biota
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- I have studied persistent environmental pollutants in herring (Clupea harengus), in adult guillemot (Uria aalge) and in guillemot eggs from the Baltic Sea. The studied contaminants were organochlorines (OCs); dichlorodiphenyltrichloroethanes (DDTs), polychlorinated biphenyls (PCBs), hexachlorobenzene (HCB), hexachlorocyclohexanes (HCHs), and brominated flame retardants (BFRs); polybrominated diphenylethers (PBDEs) and hexabromocyclododecane (HBCD). The highest concentration in both species was shown by p,p′DDE with a concentration in guillemot egg (geometric mean (GM) with 95% confidence interval) of 18200 (17000 – 19600) ng/g lipid weight. The BFR with the highest concentration in guillemot egg was HBCD with a GM concentration of 140 (120 – 160) ng/g lw. To extract additional and essential information from the data, not possible to obtain using only univariate or bivariate statistics, I used multivariate data analysis techniques; principal components analysis (PCA), partial least squares regression (PLS), soft independent modelling of class analogy (SIMCA), and PLS discriminant analysis (PLS-DA). I found e.g.; that there are significant negative correlations between egg weight and the concentrations of HCB and p,p'DDE; that concentrations of OCs and BFRs in the organisms co-varied so that concentrations of OCs can be used to calculate concentrations of BFRs; and, that several contaminants (e.g. HBCD) had higher concentration in guillemot egg than in guillemot muscle, that several (e.g. BDE47) showed no concentration difference between muscle and egg and that one contaminant (BDE154) showed higher concentration in the guillemot muscles than in egg. In this thesis I developed a new method, “randomly sampled ratios” (RSR), to calculate biomagnification factors (BMFs) i.e. the ratio between the concentration of a contaminant in an organism and the concentration of the same contaminant in its food. With this new method BMFs are denoted with an estimate of variation. Contaminants that biomagnify are e.g., p,p′DDE, CB118, HCB, βHCH and all of the BFRs. Those that do not biomagnify are e.g., p,p′DDT, αHCH and CB101. Lastly, to investigate which of the contaminants descriptors (physical-chemical/other properties and characteristics) that correlates to the biomagnification of the contaminants, I modeled the contaminants’ respective BMFRSR versus ~100 descriptors and showed that ~20 descriptors in combination were important, either favoring or counteracting biomagnification between herring and guillemot.
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| 9. |
- Wallberg, Petra, 1965-
(författare)
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Distribution and fate of polychlorinated biphenyls within the pelagic microbial food web
- 1998
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The composition and production of the plankton community in aquatic environments will in turn influence the food-web structure of larger predators, nutrient cycling, the sinking flux and, hence, the fate of hydrophobic organic contaminants. The aim of the research presented here was to study the distribution and fate of PCBs within the microbial food web, including bacteria, flagellates, ciliates, and phytoplankton. For this purpose mechanistic studies was conducted with three 14C-labelled PCBs as model substances; 4-chlorobiphenyl (UPAC # 3), 2,2',5,5'-tetrachlorobiphenyl (UPAC # 52), and 2,2',4,4',5,5'-hexachlorobiphenyl (UPAC # 153). In order to be able to interpret the behaviour and attempt to predict the fate of the PCBs the experiments were done in conjunction with estimates of biological and chemical parameters. Further, to study possible connections between the food web structure and the fate of PCBs experiments were performed with natural seawater collected at two different sites; the northern Baltic Sea (Sweden), and the Indian Ocean (outside Zanzibar Island, Tanzania). In addition to PCB experiments, seasonal and diel studies of the abundance and production of plankton organisms were conducted on Zanzibar Island with the aim of establishing carbon budgets for a rainy and a dry season.To follow the distribution of PCBs between different microorganism groups over time, the organism size fractions were separated by filtration and defined as bacteria (0.2-2 (m), flagellates (2-10 (m), and ciliates and phytoplankton (>10 (m). The largest fraction of the PCBs were sorbed to the bacteria, but the proportion of the PCB that partitioned into the larger organism groups generally showed a tendency to increase with hydrophobicity. The efficiency of the transport of PCBs from bacteria to higher trophic levels increased with chlorination, but was also found to be dependent on factors like production rates and the composition of the plankton community.In seasonal and diel studies of plankton communities in a tropical coastal ecosystem, the abundance of heterotrophic microorganisms did not significantly differ between the seasons, but the production rates for heterotrophic bacteria and flagellates were significantly higher during the rainy season. A high correlation between the abundance of heterotrophic nanoflagellates and picocyanobacteria suggests that picocyanobacteria was an important food resource for nanoflagellates. In both the seasonal and the diel study the carbon flow through the heterotrophic food chain increased with a factor of approximately 3 during the rainy season compared with the dry season. Similarly, the concentration of the hexachlorobiphenyl in the microplankton fraction was almost three times higher in experiments conducted during the rainy season than during the dry season. Results from the carbon budgets suggests that the microbial food web may be of particular significance as a food resource for higher trophic levels during the dry season.
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| 10. |
- Berggren, Hanna
(författare)
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Consequences of Environmental Variation for Fish and Their Skin Associated Microbial Communities
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Environmental conditions that vary in space and time influence the distribution, abundance, diversity and evolution of individuals, populations, species and communities. This thesis explores how environmental variation affects diversity at different levels of biological organization, and across a wide range of spatiotemporal scales, by studying fish and their associated microbiomes. The specific aims were to investigate i) effects of coarse- and fine-scale environmental variation for the performance of fish populations and individuals, and ii) ecological drivers impacting the structure and dynamics of microbial communities associated with fish hosts.For the first aim, I studied effects of environmental variation both within and between local habitats, by comparing populations of spawning migrating pike and monitor sun-basking behaviour of carp individuals. Results revealed that natal spawning site fidelity can promote evolution of local adaptations and population differentiation on relatively fine spatial scales in relation to the species dispersal capacity. I also demonstrated that fish can actively thermo-regulate and attain body temperatures in excess of the surrounding water by sun-basking, and that this translates into faster growth. Homing and sun-basking behaviour thus are important drivers of phenotypic diversity among and within populations and can also - as it turned out - influence the microbial communities associated with fish skin.For the second aim, I used a mixture of observational and experimental approaches to characterize and identify sources of variation in microbial communities associated with fish skin of perch, roach and carp. An important finding was that fish skin microbiomes are highly dynamic biodiversity hotspots. Results further suggested that variation in the assembly, composition, spatial structure, and temporal shifts of these microbiomes are influenced by stochastic events in combination with ecological filtering imposed by environment and host phenotype, most notably behaviour. A key conclusion that emerges from this thesis is that diversity at one level of biological organisation seems to support and increase diversity at a higher hierarchical level of organisation. My thesis thus adds to the knowledge, and contribute new understanding and insight into, how environmental heterogeneity and the complex interplay between different species and hierarchical levels generate and maintain biodiversity.
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