| 1. |
- Ariza, A., et al.
(författare)
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Structure and Activity of a Paenibacillus polymyxa Xyloglucanase from Glycoside Hydrolase Family 44
- 2011
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 286:39, s. 33890-33900
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Tidskriftsartikel (refereegranskat)abstract
- The enzymatic degradation of plant polysaccharides is emerging as one of the key environmental goals of the early 21st century, impacting on many processes in the textile and detergent industries as well as biomass conversion to biofuels. One of the well known problems with the use of nonstarch (nonfood)-based substrates such as the plant cell wall is that the cellulose fibers are embedded in a network of diverse polysaccharides, including xyloglucan, that renders access difficult. There is therefore increasing interest in the "accessory enzymes," including xyloglucanases, that may aid biomass degradation through removal of "hemicellulose" polysaccharides. Here, we report the biochemical characterization of the endo-beta-1,4-(xylo)glucan hydrolase from Paenibacillus polymyxa with polymeric, oligomeric, and defined chromogenic aryl-oligosaccharide substrates. The enzyme displays an unusual specificity on defined xyloglucan oligosaccharides, cleaving the XXXG-XXXG repeat into XXX and GXXXG. Kinetic analysis on defined oligosaccharides and on aryl-glycosides suggests that both the -4 and +1 subsites show discrimination against xylose-appended glucosides. The three-dimensional structures of PpXG44 have been solved both in apo-form and as a series of ligand complexes that map the -3 to -1 and +1 to +5 subsites of the extended ligand binding cleft. Complex structures are consistent with partial intolerance of xylosides in the -4' subsites. The atypical specificity of PpXG44 may thus find use in industrial processes involving xyloglucan degradation, such as biomass conversion, or in the emerging exciting applications of defined xyloglucans in food, pharmaceuticals, and cellulose fiber modification.
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| 2. |
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| 3. |
- Baumann, Martin J., et al.
(författare)
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Structural evidence for the evolution of xyloglucanase activity from xyloglucan endo-transglycosylases : Biological implications for cell wall metabolism
- 2007
-
Ingår i: The Plant Cell. - : Oxford University Press (OUP). - 1040-4651 .- 1532-298X. ; 19:6, s. 1947-1963
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Tidskriftsartikel (refereegranskat)abstract
- High-resolution, three-dimensional structures of the archetypal glycoside hydrolase family 16 (GH16) endo-xyloglucanases Tm-NXG1 and Tm-NXG2 from nasturtium (Tropaeolum majus) have been solved by x-ray crystallography. Key structural features that modulate the relative rates of substrate hydrolysis to transglycosylation in the GH16 xyloglucan-active enzymes were identified by structure-function studies of the recombinantly expressed enzymes in comparison with data for the strict xyloglucan endo-transglycosylase Ptt-XET16-34 from hybrid aspen ( Populus tremula 3 Populus tremuloides). Production of the loop deletion variant Tm-NXG1-Delta YNIIG yielded an enzyme that was structurally similar to Ptt- XET16-34 and had a greatly increased transglycosylation: hydrolysis ratio. Comprehensive bioinformatic analyses of XTH gene products, together with detailed kinetic data, strongly suggest that xyloglucanase activity has evolved as a gain of function in an ancestral GH16 XET to meet specific biological requirements during seed germination, fruit ripening, and rapid wall expansion.
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| 4. |
- Binzer, Amrei, et al.
(författare)
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The susceptibility of species to extinctions in model communities
- 2011
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Ingår i: Basic and Applied Ecology. - : Elsevier. - 1439-1791 .- 1618-0089. ; 12:7, s. 590-599
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Tidskriftsartikel (refereegranskat)abstract
- Despite the fact that the loss of a species from a community has the potential to cause a dramatic decline in biodiversity, for example through cascades of secondary extinctions, little is known about the factors contributing to the extinction risk of any particular species. Here we expand earlier modeling approaches using a dynamic food-web model that accounts for bottom-up as well as top-down effects. We investigate what factors influence a species’ extinction risk and time to extinction of the non-persistent species. We identified three basic properties that affect a species’ risk of extinction. The highest extinction risk is born by species with (1) low energy input (e.g. high trophic level), (2) susceptibility to the loss of energy pathways (e.g. specialists with few prey species) and (3) dynamic instability (e.g. low Hill exponent and reliance on homogeneous energy channels when feeding on similarly sized prey). Interestingly, and different from field studies, we found that the trophic level and not the body mass of a species influences its extinction risk. On the other hand, body mass is the single most important factor determining the time to extinction of a species, resulting in small species dying first. This suggests that in the field the trophic level might have more influence on the extinction risk than presently recognized.
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| 5. |
- Curtsdotter, Alva, et al.
(författare)
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Robustness to secondary extinctions: Comparing trait-based sequential deletions in static and dynamic food webs
- 2011
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Ingår i: Basic and Applied Ecology. - : Elsevier. - 1439-1791 .- 1618-0089. ; 12:7, s. 571-580
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Tidskriftsartikel (refereegranskat)abstract
- The loss of species from ecological communities can unleash a cascade of secondary extinctions, the risk and extent of which are likely to depend on the traits of the species that are lost from the community. To identify species traits that have the greatest impact on food web robustness to species loss we here subject allometrically scaled, dynamical food web models to several deletion sequences based on species’ connectivity, generality, vulnerability or body mass. Further, to evaluate the relative importance of dynamical to topological effects we compare robustness between dynamical and purely topological models. This comparison reveals that the topological approach overestimates robustness in general and for certain sequences in particular. Top-down directed sequences have no or very low impact on robustness in topological analyses, while the dynamical analysis reveals that they may be as important as high-impact bottom-up directed sequences. Moreover, there are no deletion sequences that result, on average, in no or very few secondary extinctions in the dynamical approach. Instead, the least detrimental sequence in the dynamical approach yields an average robustness similar to the most detrimental (non-basal) deletion sequence in the topological approach. Hence, a topological analysis may lead to erroneous conclusions concerning both the relative and the absolute importance of different species traits for robustness. The dynamical sequential deletion analysis shows that food webs are least robust to the loss of species that have many trophic links or that occupy low trophic levels. In contrast to previous studies we can infer, albeit indirectly, that secondary extinctions were triggered by both bottom-up and top-down cascades.
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| 6. |
- Eklöf, Jens, 1979-
(författare)
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A holistic approach to understanding CAZy families through reductionist methods
- 2009
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In a time when the amount of biological data present in the public domain is becoming increasingly vast, the need for good classification systems has never been greater. In the field of glycoscience the necessity of a good classification for the enzymes involved in the biosynthesis, modification and degradation of polysaccharides is even more pronounced than in other fields. This is due to the complexity of the substrates, the polysaccharides, as the theoretical number of possible hexa-oligosaccharides from only hexoses exceeds 1012 isomers! An initiative to classify enzymes acting on carbohydrates began around 1990 by the French scientist Bernard Henrissat. The resulting database, the Carbohydrate Active enzymes database (CAZy), classifies enzymes by sequence similarity into families allowing the inference of structure and catalytic mechanism. What CAZy does not provide however, are means to understand how members of a family are related, and in what way they differ from each other. The top-down approach used in this thesis, combining phylogenetic analysis of whole CAZy families, or sub-families, with structural determinations and detailed kinetic analysis allows for exactly that. Finding determinants for transglycosylation versus hydrolysis within the xth gene product family of GH16 as well as restricting the hydrolytic enzymes to a well defined clade are integral parts of paper I. In paper II a new bacterial sub-clade within CE8 was discovered. The structural determination of theEscherichia coli outer membrane lipoprotein YbhC from from the new sub-clade explained the difference in specificity. The information provided in the two papers of this thesis gives a better understanding of the development of different specificities of diverse CAZY families as well as it aids in future gene product annotations. Furthermore this work has begun to fill the white spots uncovered in the phylogenetic trees.
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| 7. |
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| 8. |
- Eklöf, Johan, et al.
(författare)
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Attitudes towards Bats in Swedish History
- 2021
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Ingår i: Journal of Ethnobiology. - : Society of Ethnobiology. - 0278-0771. ; 41:1, s. 35-52
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Tidskriftsartikel (refereegranskat)abstract
- Bats have always fascinated people by their unusual appearance, but fear towards them is also common, particularly in Western societies. Making headlines worldwide during the recent COVID-19 pandemic, bats were all too often accused of carrying and transmitting a disproportionate share of dangerous viruses. We enquired about the origin and persistence of this thinking in Sweden by searching old literature and original museum records where bats are mentioned. In the Bible, the bat is an explicitly unclean animal. At least since the Middle Ages, it has been used as a symbol of the Devil, with the dark skin wings in deliberate contrast to the white wings of angels. However, according to our folklore records, the bat was usually seen in a different and generally positive context by the people, and was treated with respect. Its magic properties, particularly contained in the blood, eyes, and wings, could bring fortune and prevent bad luck in various everyday contexts. A minority of records refer to bats being used in witchcraft, black magic, or, following the religious dogma, claiming that they are ugly or unclean and cannot be the work of God. We found no indication that bats were considered aggressive, dangerous, or to carry disease. Hence, we surmise there was little fear of bats in Swedish (Nordic) history, despite the religious message. Hence, the general attitude towards bats in the past seems to have been opposite to the view currently met in Western societies.
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| 9. |
- Eklöf, Jens M., et al.
(författare)
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Structure-function analysis of a broad specificity Populus trichocarpa endo-β-glucanase reveals an evolutionary link between bacterial licheninases and plant XTH gene products
- 2013
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 288:22, s. 15786-15799
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Tidskriftsartikel (refereegranskat)abstract
- The large xyloglucan endotransglycosylase/hydrolase (XTH) gene family continues to be the focus of much attention in studies of plant cell wall morphogenesis due to the unique catalytic functions of the enzymes it encodes. The XTH gene products compose a subfamily of glycoside hydrolase family 16 (GH16), which also comprises a broad range of microbial endoglucanases and endogalactanases, as well as yeast cell wall chitin/β-glucan transglycosylases. Previous whole-family phylogenetic analyses have suggested that the closest relatives to the XTH gene products are the bacterial licheninases (EC 3.2.1.73), which specifically hydrolyze linear mixed linkage β(1→3)/β(1→4)-glucans. In addition to their specificity for the highly branched xyloglucan polysaccharide, XTH gene products are distinguished from the licheninases and other GH16 enzyme subfamilies by significant active site loop alterations and a large C-terminal extension. Given these differences, the molecular evolution of the XTH gene products in GH16 has remained enigmatic. Here, we present the biochemical and structural analysis of a unique, mixed function endoglucanase from black cottonwood (Populus trichocarpa), which reveals a small, newly recognized subfamily of GH16 members intermediate between the bacterial licheninases and plant XTH gene products. We postulate that this clade comprises an important link in the evolution of the large plant XTH gene families from a putative microbial ancestor. As such, this analysis provides new insights into the diversification of GH16 and further unites the apparently disparate members of this important family of proteins.
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| 10. |
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| 11. |
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| 12. |
- Eklöf, Jens, 1979-
(författare)
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Plant and microbial xyloglucanases: Function, Structure and Phylogeny
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis, enzymes acting on the primary cell wall hemicellulose xyloglucan are studied. Xyloglucans are ubiquitous in land plants which make them an important polysaccharide to utilise for microbes and a potentially interesting raw material for various industries. The function of xyloglucans in plants is mainly to improve primary cell wall characteristics by coating and tethering cellulose microfibrils together. Some plants also utilise xyloglucans as storage polysaccharides in their seeds. In microbes, a variety of different enzymes for degrading xyloglucans have been found. In this thesis, the structure-function relationship of three different microbial endo-xyloglucanases from glycoside hydrolase families 5, 12 and 44 are probed and reveal details of the natural diversity found in xyloglucanases. Hopefully, a better understanding of how xyloglucanases recognise and degrade their substrate can lead to improved saccharification processes of plant matter, finding uses in for example biofuel production. In plants, xyloglucans are modified in muro by the xyloglucan transglycosylase/hydrolase (XTH) gene products. Interestingly, closely related XTH gene products catalyse either transglycosylation (XET activity) or hydrolysis (XEH activity) with dramatically different effects on xyloglucan and on cell wall characteristics. The strict transglycosylases transfer xyloglucan segments between individual xyloglucan molecules while the hydrolases degrade xyloglucan into oligosaccharides. Here, we describe and determine, a major determinant of transglycosylation versus hydrolysis in XTH gene products by solving and comparing the first 3D structure of an XEH, Tm-NXG1 and a XET, PttXET16-34. The XEH activity was hypothesised, and later confirmed to be restricted to subset of the XTH gene products. The in situ localisation of XEH activity in roots and hypocotyls of Arabidopsis was also visualised for the first time. Furthermore, an evolutionary scheme for how XTH gene products developed from bacterial beta-1,3;1,4 glucanases was also presented based on the characterisation of a novel plant endo-glucanase, PtEG16-1. The EG16s are proposed to predate XTH gene products and are with activity on both xyloglucan and beta-1,3;1,4 glucans an “intermediate” in the evolution from beta-1,3;1,4 glucanases to XTH gene products.
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| 13. |
- Eklöf, Karin, et al.
(författare)
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Brownification on hold : What traditional analyses miss in extended surface water records
- 2021
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Ingår i: Water Research. - : Elsevier Ltd. - 0043-1354 .- 1879-2448. ; 203
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Tidskriftsartikel (refereegranskat)abstract
- Widespread increases in organic matter (OM) content of surface waters, as measured by color and organic carbon (OC), are a major issue for aquatic ecosystems. Long-term monitoring programs revealed the issue of “brownification”, with climate change, land cover changes and recovery from acidification all suspected to be major drivers or contributing factors. While many studies have focused on the impact and drivers, fewer have followed up on whether brownification is continuing. As time-series of OM data lengthen, conventional data-analysis approaches miss important information on when changes occur. To better identify temporal OM patterns during three decades (1990–2020) of systematic monitoring, we used generalized additive models to analyze 164 time-series from watercourses located across Sweden. Increases in OC that were widespread during 1990–2010 ceased a decade ago, and most color increases ceased 20 years ago. These findings highlight the need to reassess the understanding of brownification's spatial and temporal extent, as well as the tools used to analyze lengthening time series.
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| 14. |
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| 15. |
- Eklöf, Karin, et al.
(författare)
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Spatial and temporal variation of THg concentrations in run-off water from 19 boreal catchments, 2000-2010
- 2012
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Ingår i: Environmental Pollution. - : Elsevier BV. - 0269-7491 .- 1873-6424. ; 164, s. 102-109
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Tidskriftsartikel (refereegranskat)abstract
- Total mercury concentrations are presented for 19 Swedish watercourses 2000-2010, together with an analysis of factors affecting these concentrations in space and time. Organic matter (OM) measured as absorbance at 420 nm (Abs(420)) and total organic carbon (TOC) were the variables most strongly correlated with THg concentrations in the pooled dataset from all 19 watercourses, explaining 66% and 61% of the variance respectively. The correlation between THg and OM indicates that OM is the main controlling factor independent of geographical variation in Hg deposition, geology, or any other factor evaluated in this study. Despite an increase in TOC concentrations at most sites during the study period, THg increased in only one of the watercourses, and the THg/TOC ratio decreased significantly at six sites. The Abs(420) did not increase like TOC. We suggest that OM-fractions absorbing at 420 nm are more important for Hg mobilization than other OM-fractions.
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| 16. |
- Eklöf, Mats, et al.
(författare)
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Workplace intervention for improved risk perception and preventive activity among workers : using hand-held vibrating machines: a pilot study
- 2023
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This article presents a pilot study of a 1-h workplace educational intervention implemented among ten construction workers who were highly exposed to hand–arm vibration. The intervention combined risk communication and normative expert advice intended to reinforce preventive behaviour related to vibration, noise, and biomechanical loads. Data for this study comprised intervention notes and interview data from interventionists, and pre- and post-intervention interview data from participating workers.The results suggested that the intervention was sensitive to disturbances and should be directed only to motivated workers possessing sufficient self-efficacy, and only in circumstances in which exposure may be controlled on the local workplace level and by locally implemented measures. Unless these conditions are present, the studied intervention may fail to influence preventive behaviour, and may instead cause cognitive dissonance and frustration among participants and interventionists.
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| 17. |
- Eriksson, Britas Klemens, et al.
(författare)
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Effects of Altered Offshore Food Webs on Coastal Ecosystems Emphasize the Need for Cross-Ecosystem Management
- 2011
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Ingår i: Ambio. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 40:7, s. 786-797
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Forskningsöversikt (refereegranskat)abstract
- By mainly targeting larger predatory fish, commercial fisheries have indirectly promoted rapid increases in densities of their prey; smaller predatory fish like sprat, stickleback and gobies. This process, known as mesopredator release, has effectively transformed many marine offshore basins into mesopredator-dominated ecosystems. In this article, we discuss recent indications of trophic cascades on the Atlantic and Baltic coasts of Sweden, where increased abundances of mesopredatory fish are linked to increased nearshore production and biomass of ephemeral algae. Based on synthesis of monitoring data, we suggest that offshore exploitation of larger predatory fish has contributed to the increase in mesopredator fish also along the coasts, with indirect negative effects on important benthic habitats and coastal water quality. The results emphasize the need to rebuild offshore and coastal populations of larger predatory fish to levels where they regain their control over lower trophic levels and important links between offshore and coastal systems are restored.
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| 18. |
- Eriksson, Britas Klemens, et al.
(författare)
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Habitat segregation of plate phenotypes in a rapidly expanding population of three-spined stickleback
- 2021
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Ingår i: Ecosphere. - : Wiley. - 2150-8925 .- 2150-8925. ; 12:6
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Tidskriftsartikel (refereegranskat)abstract
- Declines of large predatory fish due to overexploitation are restructuring food webs across the globe. It is now becoming evident that restoring these altered food webs requires addressing not only ecological processes, but evolutionary ones as well, because human-induced rapid evolution may in turn affect ecological dynamics. We studied the potential for niche differentiation between different plate armor phenotypes in a rapidly expanding population of a small prey fish, the three-spined stickleback (Gasterosteus aculeatus). In the central Baltic Sea, three-spined stickleback abundance has increased dramatically during the past decades. The increase in this typical mesopredator has restructured near-shore food webs, increased filamentous algal blooms, and threatens coastal biodiversity. Time-series data covering 22 years show that the increase coincides with a decline in the number of juvenile perch (Perca fluviatilis), the most abundant predator of stickleback along the coast. We investigated the distribution of different stickleback plate armor phenotypes depending on latitude, environmental conditions, predator and prey abundances, nutrients, and benthic production; and described the stomach content of the stickleback phenotypes using metabarcoding. We found two distinct lateral armor plate phenotypes of stickleback, incompletely and completely plated. The proportion of incompletely plated individuals increased with increasing benthic production and decreasing abundances of adult perch. Metabarcoding showed that the stomach content of the completely plated individuals more often contained invertebrate herbivores (amphipods) than the incompletely plated ones. Since armor plates are defense structures favored by natural selection in the presence of fish predators, the phenotype distribution suggests that a novel low-predation regime favors stickleback with less armor. Our results suggest that morphological differentiation of the three-spined stickleback has the potential to affect food web dynamics and influence the persistence and resilience of the stickleback take-over in the Baltic Sea.
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| 19. |
- Gloster, Tracey M., et al.
(författare)
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Characterization and three-dimensional structures of two distinct bacterial xyloglucanases from families GH5 and GH12
- 2007
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 282:26, s. 19177-19189
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Tidskriftsartikel (refereegranskat)abstract
- The plant cell wall is a complex material in which the cellulose microfibrils are embedded within a mesh of other polysaccharides, some of which are loosely termed hemicellulose. One such hemicellulose is xyloglucan, which displays a beta-1,4-linked D-glucose backbone substituted with xylose, galactose, and occasionally fucose moieties. Both xyloglucan and the enzymes responsible for its modification and degradation are finding increasing prominence, reflecting both the drive for enzymatic biomass conversion, their role in detergent applications, and the utility of modified xyloglucans for cellulose fiber modification. Here we present the enzymatic characterization and three-dimensional structures in ligand free and xyloglucan- oligosaccharide complexed forms of two distinct xyloglucanases from glycoside hydrolase families GH5 and GH12. The enzymes, Paenibacillus pabuli XG5 and Bacillus licheniformis XG12, both display open active center grooves grafted upon their respective (beta/alpha)(8) and beta-jelly roll folds, in which the side chain decorations of xyloglucan may be accommodated. For the beta-jelly roll enzyme topology of GH12, binding of xylosyl and pendant galactosyl moieties is tolerated, but the enzymeis similarly competent in the degradation of unbranched glucans. In the case of the (beta/alpha)(8) GH5 enzyme, kinetically productive interactions are made with both xylose and galactose substituents, as reflected in both a high specific activity on xyloglucan and the kinetics of a series of aryl glycosides. The differential strategies for the accommodation of the side chains of xyloglucan presumably facilitate the action of these microbial hydrolases in milieus where diverse and differently substituted substrates may be encountered.
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| 20. |
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| 21. |
- Kaewthai, Nomchit, et al.
(författare)
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Group III-A XTH Genes of Arabidopsis Encode Predominant Xyloglucan Endohydrolases That Are Dispensable for Normal Growth
- 2013
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Ingår i: Plant Physiology. - : Oxford University Press (OUP). - 0032-0889 .- 1532-2548. ; 161:1, s. 440-454
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Tidskriftsartikel (refereegranskat)abstract
- The molecular basis of primary wall extension endures as one of the central enigmas in plant cell morphogenesis. Classical cell wall models suggest that xyloglucan endo-transglycosylase activity is the primary catalyst (together with expansins) of controlled cell wall loosening through the transient cleavage and religation of xyloglucan-cellulose cross links. The genome of Arabidopsis (Arabidopsis thaliana) contains 33 phylogenetically diverse XYLOGLUCAN ENDO-TRANSGLYCOSYLASE/HYDROLASE (XTH) gene products, two of which were predicted to be predominant xyloglucan endohydrolases due to clustering into group III-A. Enzyme kinetic analysis of recombinant AtXTH31 confirmed this prediction and indicated that this enzyme had similar catalytic properties to the nasturtium (Tropaeolum majus) xyloglucanase1 responsible for storage xyloglucan hydrolysis during germination. Global analysis of Genevestigator data indicated that AtXTH31 and the paralogous AtXTH32 were abundantly expressed in expanding tissues. Microscopy analysis, utilizing the resorufin beta-glycoside of the xyloglucan oligosaccharide XXXG as an in situ probe, indicated significant xyloglucan endohydrolase activity in specific regions of both roots and hypocotyls, in good correlation with transcriptomic data. Moreover, this hydrolytic activity was essentially completely eliminated in AtXTH31/AtXTH32 double knockout lines. However, single and double knockout lines, as well as individual overexpressing lines, of AtXTH31 and AtXTH32 did not demonstrate significant growth or developmental phenotypes. These results suggest that although xyloglucan polysaccharide hydrolysis occurs in parallel with primary wall expansion, morphological effects are subtle or may be compensated by other mechanisms. We hypothesize that there is likely to be an interplay between these xyloglucan endohydrolases and recently discovered apoplastic exo-glycosidases in the hydrolytic modification of matrix xyloglucans.
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| 22. |
- Maris, An, et al.
(författare)
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Differences in enzymic properties of five recombinant xyloglucan endotransglucosylase/hydrolase (XTH) proteins of Arabidopsis thaliana
- 2011
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Ingår i: Journal of Experimental Botany. - : Oxford University Press (OUP). - 0022-0957 .- 1460-2431. ; 62:1, s. 261-271
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Tidskriftsartikel (refereegranskat)abstract
- Xyloglucan endotransglucosylase/hydrolases (XTHs) are cell wall enzymes that are able to graft xyloglucan chains to oligosaccharides or to other available xyloglucan chains and/or to hydrolyse xyloglucan chains. As they are involved in the modification of the load-bearing cell-wall components, they are believed to be very important in the regulation of growth and development. Given the large number (33) of XTH genes in Arabidopsis and the overlapping expression patterns, specific enzymic properties may be expected. Five predominantly root-expressed Arabidopsis thaliana XTHs belonging to subgroup I/II were analysed here. These represent two sets of closely related genes: AtXTH12 and 13 on the one hand (trichoblast-enriched) and AtXTH17, 18, and 19 on the other (expressed in nearly all cell types in the root). They were all recombinantly produced in the yeast Pichia pastoris and partially purified by ammonium sulphate precipitation before they were subsequently all subjected to a series of identical in vitro tests. The kinetic properties of purified AtXTH13 were investigated in greater detail to rule out interference with the assays by contaminating yeast proteins. All five proteins were found to exhibit only the endotransglucosylase (XET; EC 2.4.1.207) activity towards xyloglucan and non-detectable endohydrolytic (XEH; EC 3.2.1.151) activity. Their endotransglucosylase activity was preferentially directed towards xyloglucan and, in some cases, water-soluble cellulose acetate, rather than to mixed-linkage beta-glucan. Isoforms differed in optimum pH (5.0-7.5), in temperature dependence and in acceptor substrate preferences.
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| 23. |
- Mark, Pekka, et al.
(författare)
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Analysis of nasturtium TmNXG1 complexes by crystallography and molecular dynamics provides detailed insight into substrate recognition by family GH16 xyloglucan endo-transglycosylases and endo-hydrolases
- 2009
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Ingår i: Proteins. - : Wiley. - 0887-3585 .- 1097-0134. ; 75:4, s. 820-836
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Tidskriftsartikel (refereegranskat)abstract
- Reorganization and degradation of the wall crosslinking and seed storage polysaccharide xyloglucan by glycoside hydrolase family 16 (GH16) endo-transglycosylases and hydrolases are crucial to the growth of the majority of land plants, affecting processes as diverse as germination, morphogenesis, and fruit ripening. A high-resolution, three-dimensional structure of a nasturtium (Tropaeolum majus) endo-xyloglucanase loop mutant, TmNXG1-Delta YNIIG, with an ohgosaccharide product bound in the negative active-site subsites, has been solved by X-ray crystallography. Comparison of this novel complex to that of the strict xyloglucan endotransglycosylase PttXET16-34 from hybrid aspen (Populus tremula x tremuloides), previously solved with a xylogluco-oligosaccharide bound in the positive subsites, highlighted key protein structures that affect the disparate catalytic activities displayed by these closely related enzymes. Combination of these "partial" active-site complexes through molecular dynamics simulations in water allowed modeling of wild-type TmNXG1, TmNXG1-Delta YNIIG, and wild-type PttXET16-34 in complex with a xyloglucan octadecasaccharide spanning the entire catalytic cleft. A comprehensive analysis of these full-length complexes underscored the importance of various loops lining the active site. Subtle differences leading to a tighter hydrogen bonding pattern on the negative (glycosyl donor) binding subsites, together with loop flexibility on the positive (glycosyl acceptor) binding subsites appear to favor hydrolysis over transglycosylation in GH16 xyloglucan-active enzymes.
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| 24. |
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| 25. |
- Nordgren, Niklas, 1975-, et al.
(författare)
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Top-Down Grafting of Xyloglucan to Gold Monitored by QCM-D and AFM: Enzymatic Activity and Interactions with Cellulose
- 2008
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Ingår i: Biomacromolecules. - USA : American Chemical Society. - 1525-7797 .- 1526-4602. ; 9:3, s. 942-948
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Tidskriftsartikel (refereegranskat)abstract
- This study focuses on the manufacture and characterisation of model surfaces consisting of end grafted xyloglucan (XG), a naturally occurring polysaccharide, onto a gold substrate. The now well-established XET-technology was utilised for enzymatic incorporation of a thiol moiety at one end of the xyloglucan backbone. This functionalised macromolecule was subsequently top-down grafted to gold, forming a thiol-bonded xyloglucan brush-like layer. The grafting was monitored in-situ with QCM-D and a significant difference in the adsorbed/grafted amount between unmodified xyloglucan and the thiol-functionalised polymer was observed. The grafted surface was demonstrated to be accessible to enzyme digestion using the plant endo-xyloglucanase TmNXG1. The nanotribological properties towards cellulose of the untreated crystal, brush modified surface and enzyme exposed surfaces were compared with a view to understanding the role of xyloglucan in friction reduction. Friction coefficients obtained by the AFM colloidal probe technique using a cellulose functionalised probe on the xyloglucan brush showed an increase of a factor of two after the enzyme digestion and this result is interpreted in terms of surface roughness. Finally, the brush is shown to exhibit binding to cellulose despite its highly oriented nature.
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| 26. |
- Olin, Agnes B., et al.
(författare)
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Increases of opportunistic species in response to ecosystem change : the case of the Baltic Sea three-spined stickleback
- 2022
-
Ingår i: ICES Journal of Marine Science. - : Oxford University Press (OUP). - 1054-3139 .- 1095-9289. ; 79:5, s. 1419-1434
-
Forskningsöversikt (refereegranskat)abstract
- Under rapid environmental change, opportunistic species may exhibit dramatic increases in response to the altered conditions, and can in turn have large impacts on the ecosystem. One such species is the three-spined stickleback (Gasterosteus aculeatus), which has shown substantial increases in several aquatic systems in recent decades. Here, we review the population development of the stickleback in the Baltic Sea, a large brackish water ecosystem subject to rapid environmental change. Current evidence points to predatory release being the central driver of the population increases observed in some areas, while both eutrophication and climate change have likely contributed to creating more favourable conditions for the stickleback. The increasing stickleback densities have had profound effects on coastal ecosystem function by impairing the recruitment of piscivorous fish and enhancing the effects of eutrophication through promoting the production of filamentous algae. The increase poses a challenge for both environmental management and fisheries, where a substantial interest from the pelagic fisheries fleet in exploiting the species calls for urgent attention. While significant knowledge gaps remain, we suggest that the case of the Baltic Sea stickleback increase provides generalisable lessons of value for understanding and managing other coastal ecosystems under rapid change.
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| 27. |
- Riede, Jens O, et al.
(författare)
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Size-based food web characteristics govern the response to species extinctions
- 2011
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Ingår i: Basic and Applied Ecology. - : Elsevier. - 1439-1791 .- 1618-0089. ; 12:7, s. 581-589
-
Tidskriftsartikel (refereegranskat)abstract
- How ecological communities react to species extinctions is a long-standing yet current question in ecology. The species constituting the basic units of ecosystems interact with each other forming complex networks of trophic relationships and the characteristics of these networks are highly important for the consequences of species extinction. Here we take a more general approach and analyze a broad range of network characteristics and their role in determining food web susceptibility to secondary extinctions. We extend previous studies, that have focused on the consequences of topological and dynamical foodweb parameters for food web robustness, by also defining network-wide characteristics depending on the relationships between the distribution of species body masses and other species characteristics. We use a bioenergetic dynamical model to simulate realistically structured model food webs that differ in their structural and dynamical properties as well as their size structure. In order to measure food web robustness we calculated the proportion of species going secondarily extinct. A multiple regression analysis was then used to fit a general model relating the proportion of species going secondarily extinct to the measured foodweb properties. Our results show that there are multiple factors from all three groups of food web characteristics that affect foodweb robustness. However, we find the most striking effect was related to the body mass–abundance relationship which points to the importance of body mass relationships for food web stability.
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| 28. |
- Rudjito, Reskandi C., et al.
(författare)
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Comparison of xylanases from different glycosyl hydrolase familiesfor the production of arabinoxylan-oligosaccharides with prebioticpotential
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- In this study, we compared the activity of four different xylanases (GH 5_34, 8, 10 and 11) for the production of arabinoxylan-oligosaccharide or (A)XOS from cereal arabinoxylans as potential prebiotics. In terms of efficiency, the AcXyn10A and TlXyn11 produced larger quantities of small (A)XOS of mainly X1-X3 in a shorter period of time. The BXyn8 was most restricted by high arabinose substitution but could still accommodate them at the +2 subsite. The GpXyn5_34 preferred high arabinose substitution, requiring an arabinose at the -1 subsite for cleavage. Both the BXyn8 and GpXyn5_34 produced longer (A)XOS that were mostly linear and substituted, respectively. During fermentation of (A)XOS on selected gut bacteria, the long-substituted products of GpXyn5_34 stunted the growth of B. ovatus and B. adolescentis, while the mid-length, linear products of BXyn8 favoured the growth of both bacteria.
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| 29. |
- Rudjito, Reskandi C., et al.
(författare)
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Enzyme-assisted recovery of recalcitrant feruloylated arabinoxylans in combination with subcritical water extraction
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Wheat bran (Wb) is an abundant and low valued feedstock that can be valorised for its high arabinoxylan (AX) content by means of sustainable bioprocessing. However, its recalcitrant nature in terms of molecular structure and supramolecular interactions hinders its efficient fractionation. In this study we have developed an integrated bioprocess combining consecutive rounds of subcritical water extraction (SWE) and enzymatic treatments (ET) for maximised recovery of feruloylated AXs and oligosaccharides from Wb. After the first round of SWE (SWE I), enrichment of AX was observed with increased extraction time, along with an increased complexity of the AX structure in terms of A/X ratio and ferulic acid (FA) content. The residual wheat bran (Wb-R) after SWE I was subjected to ET using two different enzymatic cocktails that were sequentially screened on Wb-R. The enzymatic cocktails contained each a feruloyl esterase (F) and a xylanase (X) from either the glycosyl hydrolase family GH10 (X10A) or GH5_21 (X5_21) respectively, with distinct activity and substrate selectivity onto complex AX. The combination of the GH10 xylanase and feruloyl esterase resulted in higher hydrolysate yields composed of mainly xylobiose (X2) and monomeric FA, while the hydrolysate from the GH5_21 xylanase and feruloyl esterase was composed of longer substituted oligo- and polysaccharides. The residues after enzymatic treatments were then subjected to a second round of SWE (SWE II). Comparatively, the SWE II extract after GH10 xylanase and feruloyl esterase treatment resulted in higher yields than the GH5_21 xylanase treatment, and the isolated AX was highly substituted (A/X: 0.7) and exhibited a high molar mass distribution (104 Da). The incorporation of selective xylanolytic enzymes in the integrated SWE bioprocess resulted in increased AX yields and produced AX with tailored molecular structure in terms of degree of substitution, molar mass, and ferulic acid content, which can potentially be used as matrices for advanced biomedical and nutritional applications.
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| 30. |
- Rudjito, Reskandi C., et al.
(författare)
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Integration of subcritical water extraction and treatment with xylanases and feruloyl esterases maximises release of feruloylated arabinoxylans from wheat bran
- 2024
-
Ingår i: Bioresource Technology. - : Elsevier BV. - 0960-8524 .- 1873-2976. ; 395
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Tidskriftsartikel (refereegranskat)abstract
- Wheat bran is an abundant and low valued agricultural feedstock rich in valuable biomolecules as arabinoxylans (AX) and ferulic acid with important functional and biological properties. An integrated bioprocess combining subcritical water extraction (SWE) and enzymatic treatments has been developed for maximised recovery of feruloylated arabinoxylans and oligosaccharides from wheat bran. A minimal enzymatic cocktail was developed combining one xylanase from different glycosyl hydrolase families and a feruloyl esterase. The incorporation of xylanolytic enzymes in the integrated SWE bioprocess increased the AX yields up to 75%, higher than traditional alkaline extraction, and SWE or enzymatic treatment alone. The process isolated AX with tailored molecular structures in terms of substitution, molar mass, and ferulic acid, which can be used for structural biomedical applications, food ingredients and prebiotics. This study demonstrates the use of hydrothermal and enzyme technologies for upcycling agricultural side streams into functional bioproducts, contributing to a circular food system.
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| 31. |
- Rudjito, Reskandi C., et al.
(författare)
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Regioselectivity and patterns of arabinose substitution and feruloylation determine the activity of xylanases from GH5
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Endo-1,4-β-xylanases from glycosyl hydrolase family 5 (GH5) prefer highly substituted arabinoxylans (AX) due to the need of arabinose decorations as a specificity determinant for cleavage. In this study, we compared the activity of GH5 xylanases from subfamilies GH5_21, GH5_34 and GH5_35, in terms of how arabinose substitutions and feruloylation are tolerated by the enzymes. We specifically prepared three AX substrates from wheat and barley bran with distinct arabinose substitution patterns and ferulic acid content. The GH5_34 xylanase was the most active in all substrates, followed by the GH5_21 and GH5_35. The regioselectivity and patterns of arabinose substitution were more important than the overall degree of arabinose substitution of the AX substrates. All the GH5 xylanases targeted C(O)-3 linked arabinose substitutions, producing oligosaccharides with a C(O)-3 linked arabinose at the reducing end. Ferulic acid (FA) slightly hindered enzymatic activity, as it obstructed the C(O)-3 linked arabinose in becoming a specificity determinant for cleavage. This study highlights the exquisitely specific nature of GH5 β-xylanases, opening new avenues for their application in tackling highly substituted recalcitrant AX substrates and for molecular tailoring of polysaccharides.
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| 32. |
- Rydell, Jens, et al.
(författare)
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Age of enlightenment : Long-term effects of outdoor aesthetic lights on bats in churches
- 2017
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Ingår i: Royal Society Open Science. - : The Royal Society. - 2054-5703. ; 4:8
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Tidskriftsartikel (refereegranskat)abstract
- We surveyed 110 country churches in south-western Sweden for presence of brown long-eared bats Plecotus auritus in summer 2016 by visual inspection and/or evening emergence counts. Each church was also classified according to the presence and amount of aesthetic directional lights (flood-lights) aimed on its walls and tower from the outside. Sixty-one of the churches had previously been surveyed by one of us (J.R.) between 1980 and 1990, before lights were installed on Swedish churches, using the same methods. Churches with bat colonies had decreased significantly in frequency from 61% in 1980s to 38% by 2016. All abandoned churches had been fitted with flood-lights in the period between the two surveys. The loss of bat colonies from lit churches was highly significant and most obvious when lights were applied from all directions, leaving no dark corridor for the bats to leave and return to the roost. In contrast, in churches that were not lit, all of 13 bat colonies remained after 25+ years between the surveys. Lighting of churches and other historical buildings is a serious threat to the long-term survival and reproduction of light-averse bats such as Plecotus spp. and other slow-flying species. Bat roosts are strictly protected according to the EU Habitats Directive and the EUROBATS agreement. Lighting of buildings for aesthetic purposes is becoming a serious environmental issue, because important bat roosts are destroyed in large numbers, and the problem should be handled accordingly. As a start, installation of flood-lights on historical buildings should at least require an environmental impact assessment (EIA).
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| 33. |
- Rydell, Jens, et al.
(författare)
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Dramatic decline of northern bat Eptesicus nilssonii in Sweden over 30 years
- 2020
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Ingår i: Royal Society Open Science. - : The Royal Society. - 2054-5703. ; 7:2
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Tidskriftsartikel (refereegranskat)abstract
- We monitored northern bat Eptesicus nilssonii (Keyserling & Blasius, 1839) acoustically along a 27 km road transect at weekly intervals in 1988, 1989 and 1990, and again in 2016 and 2017. The methodology of data collection and the transect were the same throughout, except that the insect-attracting mercury-vapour street-lights along parts of the road were replaced by sodium lights between the two survey periods. Counts along sections of the transect with and without streetlights were analysed separately. The frequency of bat encounters in unlit sections showed an average decline of 3.0% per year, corresponding to a reduction of 59% between 1988 and 2017. Sections with street-lights showed an 85% decline over the same period (6.3% per year). The decline represents a real reduction in the abundance of bats rather than an artefact of changed distribution of bats away from roads. Our study conforms with another long-term survey of the same species on the Baltic island of Gotland. Our results agree with predictions based on climate change models. They also indicate that the decline was caused directly by the disuse of the insect-attracting mercury-vapour street-lights, which may have resulted in lower availability of preferred prey (moths). In the 1980s, E. nilssonii was considered the most common bat in Sweden, but the subsequent decline would rather qualify it for vulnerable or endangered status in the national Red List of Threatened Species.
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| 34. |
- Rydell, Jens, et al.
(författare)
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How to leave the church : light avoidance by brown long-eared bats
- 2021
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Ingår i: Mammalian Biology. - : Springer Science and Business Media LLC. - 1616-5047 .- 1618-1476. ; 101:6, s. 979-986
-
Tidskriftsartikel (refereegranskat)abstract
- Light pollution, light in the wrong place at the wrong time, is an emerging environmental issue with wide-ranging consequences. It interferes with the fundamental 24 h light–dark cycle, and has biological effects at all levels, from molecules to ecosystems, including human health and welfare. Here, exemplified by flood-lit churches, artificial lights compromise the survival of resident bats, as darkness provides protection from predation. We predicted that brown long-eared bats Plecotus auritus emerging from churches should (1) avoid illuminated church walls, and (2) avoid extended flights in the open. To test these predictions, bats were observed emerging from 33 country churches in Sweden. A model for light intensity at increasing distances from light sources was made. This model, in combination with known distance between church walls and surrounding lamps, was used to predict lux levels (lx) at each church wall. Higher light intensities were strictly avoided and the majority of bats emerged when light intensities at church walls were below 1.25 lx. Further, most brown long-eared bats flew into the canopy of trees less than 15 m distant from the churches. Bats and their roosts are strictly protected in Europe, but this is poorly enforced with respect to churches and other historical buildings. Nevertheless, lighting of buildings is a key issue in bat conservation and of worldwide significance. We strongly advise that installation of lights near historical buildings is regulated and subject to environmental impact assessments.
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| 35. |
- Rydell, Jens, et al.
(författare)
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Long-Term Increase in Hibernating Bats in Swedish Mines - Effect of Global Warming?
- 2018
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Ingår i: Acta Chiropterologica. - 1508-1109. ; 20:2, s. 421-426
-
Tidskriftsartikel (refereegranskat)abstract
- We present the result of bat winter censuses in three old mines in southern Sweden from 1980 until present (2017). The Taberg and Kleva mines, each with about 1.5 km of accessible passages, have winter populations of 517 and 132 bats, respectively (maximum counts) belonging to six species, the highest numbers known in underground sites in Sweden. Ädelfors is less extensive and has fewer individuals (maximum 22). The two former sites were protected and gated in the 1980′s while the third site still has no formal protection and is subject to disturbance. Generally Daubenton's bat Myotis daubentonii and the brown long-eared bat Plecotus auritus are common species and the numbers are stable. The whiskered and Brandt's bats M. mystacinus/brandtii and Natterer's bat M. nattereri have increased significantly, while the northern bat Eptesicus nilssonii, which is relatively rare in mines generally, has shown a slight but significant decline. At the species level the population trends conform well to those of the respective species in continental Europe and the British Isles. This suggests that there is a common factor behind the population changes across Europe. Although our data are very limited, the results question some previous explanations for the observed trends, but are in line with theoretical predictions based on global warming scenarios.
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| 36. |
- Rydell, Jens, et al.
(författare)
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Testing the performances of automated identification of bat echolocation calls : A request for prudence
- 2017
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Ingår i: Ecological Indicators. - : Elsevier BV. - 1470-160X. ; 78, s. 416-420
-
Tidskriftsartikel (refereegranskat)abstract
- Echolocating bats are surveyed and studied acoustically with bat detectors routinely and worldwide, yet identification of species from calls often remains ambiguous or impossible due to intraspecific call variation and/or interspecific overlap in call design. To overcome such difficulties and to reduce workload, automated classifiers of echolocation calls have become popular, but their performance has not been tested sufficiently in the field. We examined the absolute performance of two commercially available programs (SonoChiro and Kaleidoscope) and one freeware package (BatClassify). We recorded noise from rain and calls of seven common bat species with Pettersson real-time full spectrum detectors in Sweden. The programs could always (100%) distinguish rain from bat calls, usually (68–100%) identify bats to group (Nyctalus/Vespertilio/Eptesicus, Pipistrellus, Myotis, Plecotus, Barbastella) and usually (83–99%) recognize typical calls of some species whose echolocation pulses are structurally distinct (Pipistrellus pygmaeus, Barbastella barbastellus). Species with less characteristic echolocation calls were not identified reliably, including Vespertilio murinus (16–26%), Myotis spp. (4–93%) and Plecotus auritus (0–89%). All programs showed major although different shortcomings and the often poor performance raising serious concerns about the use of automated classifiers for identification to species level in research and surveys. We highlight the importance of validating output from automated classifiers, and restricting their use to specific situations where identification can be made with high confidence. For comparison we also present the result of a manual identification test on a random subset of the files used to test the programs. It showed a higher classification success but performances were still low for more problematic taxa.
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| 37. |
- Stepper, Judith, et al.
(författare)
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Structure and activity of the Streptococcus pyogenes family GH1 6-phospho-beta-glucosidase SPy1599
- 2013
-
Ingår i: Acta Crystallographica Section D. - 0907-4449 .- 1399-0047. ; 69, s. 16-23
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Tidskriftsartikel (refereegranskat)abstract
- The group A streptococcus Streptococcus pyogenes is the causative agent of a wide spectrum of invasive infections, including necrotizing fasciitis, scarlet fever and toxic shock syndrome. In the context of its carbohydrate chemistry, it is interesting that S. pyogenes (in this work strain M1 GAS SF370) displays a spectrum of oligosaccharide-processing enzymes that are located in close proximity on the genome but that the in vivo function of these proteins remains unknown. These proteins include different sugar transporters (SPy1593 and SPy1595), both GH125 alpha-1,6- and GH38 alpha-1,3-mannosidases (SPy1603 and SPy1604), a GH84 beta-hexosaminidase (SPy1600) and a putative GH2 beta-galactosidase (SPy1586), as well as SPy1599, a family GH1 'putative beta-glucosidase'. Here, the solution of the three-dimensional structure of SPy1599 in a number of crystal forms complicated by unusual crystallographic twinning is reported. The structure is a classical (beta/alpha)(g)-barrel, consistent with CAZy family GH1 and other members of the GH-A clan. SPy1599 has been annotated in sequence depositions as a beta-glucosidase (EC 3.2.1.21), but no such activity could be found; instead, three-dimensional structural overlaps with other enzymes of known function suggested that SPy1599 contains a phosphate-binding pocket in the active site and has possible 6-phospho-beta-glycosidase activity. Subsequent kinetic analysis indeed showed that SPy1599 has 6-phospho-beta-glucosidase (EC 3.2.1.86) activity. These data suggest that SPy1599 is involved in the intracellular degradation of 6-phosphoglycosides, which are likely to originate from import through one of the organism's many phosphoenolpyruvate phosphotransfer systems (PEP-PTSs).
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| 38. |
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| 39. |
- Svensson, Filip, et al.
(författare)
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In situ warming strengthens trophic cascades in a coastal food web
- 2017
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Ingår i: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 126:8, s. 1150-1161
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Tidskriftsartikel (refereegranskat)abstract
- Global warming may affect most organisms and their interactions. Theory and simple mesocosm experiments suggest that consumer top-down control over primary producer biomass should strengthen with warming, since consumer respiration increases faster with warming than plant photosynthesis. However, these predictions have so far not been tested on natural communities that have experienced warming over many generations. Natural systems display a higher diversity, heterogeneity and complexity than mesocosms, which could alter predicted effects of warming. Here we used an artificially heated part of the northern Baltic Sea (the Forsmark Biotest basin) to test how warming influences trophic interactions in a shallow coastal food web with four trophic levels: omnivorous fish, invertivorous fish, herbivorous invertebrates, and filamentous macroalgae. Monitoring of fish assemblages over six years showed that small invertivorous fish (gobiids, sticklebacks and minnows) were much less abundant in the heated basin than in unheated references areas. Stomach content analyses of the dominating omnivorous fish - Eurasian perch Perca fluviatilis - revealed a strikingly different diet within and outside the Biotest basin; gammarid crustaceans were the dominating prey at heated sites, whereas invertivorous fish (e.g. gobiids) dominated at unheated sites. A 45-day cage experiment showed that fish exclusion did not affect the biomass of algal herbivores (gastropods and gammarids), but reduced algal biomass in heated sites (but not unheated). This suggests that warming induced a trophic cascade from fish to algae, and that this effect was mediated by predator-induced changes in herbivore behavior, rather than number. Overall, our study suggests that warming has effectively compressed the food chain from four to three trophic levels (algae, gammarids and perch), which have benefitted the primary producers by reducing grazing pressure. Consequently, warming appears to have restructured this coastal food web through a combination of direct (physiological) and indirect (species interactions) effects.
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| 40. |
- Von Brömssen, Claudia, et al.
(författare)
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A toolbox for visualizing trends in large-scale environmental data
- 2021
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Ingår i: Environmental Modelling and Software. - : Elsevier BV. - 1364-8152 .- 1873-6726. ; 136
-
Tidskriftsartikel (refereegranskat)abstract
- Generalized additive models are increasingly used to identify and describe environmental trends. A major advantage of these models, as compared to simpler statistical tools such as linear regression or Mann-Kendall tests, is that they provide estimates of prevailing levels and trend magnitudes at any given point in time instead of an overall measure. For multiple time series, this versatility has to be followed by flexible visualization methods that can summarize and visualize trend analysis results for many series simultaneously. Here, we propose several types of visualizations and illustrate the methods by showing trends in variables related to the recovery from acidification in Swedish riverine data over the period 1988-2017. By this, we show that generalized additive models, together with a small number of selected plots, can comprehensively illustrate prevailing trends and summarize complex information from multiple series.
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| 41. |
- Von Brömssen, Claudia, et al.
(författare)
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Temporal trend evaluation in monitoring programs with high spatial resolution and low temporal resolution using geographically weighted regression models
- 2023
-
Ingår i: Environmental Monitoring and Assessment. - 0167-6369 .- 1573-2959. ; 195
-
Tidskriftsartikel (refereegranskat)abstract
- Data from monitoring programs with high spatial resolution but low temporal resolution are often overlooked when assessing temporal trends, as the data structure does not permit the use of established trend analysis methods. However, the data include uniquely detailed information about geographically differentiated temporal trends driven by large-scale influences, such as climate or airborne deposition. In this study, we used geographically weighted regression models, extended with a temporal component, to evaluate linear and nonlinear trends in environmental monitoring data. To improve the results, we tested approaches for station-wise pre-processing of data and for validation of the resulting models. To illustrate the method, we used data on changes in total organic carbon (TOC) obtained in a monitoring program of around 4800 Swedish lakes observed once every 6 years between 2008 and 2021. On applying the methods developed here, we identified nonlinear changes in TOC from consistent negative trends over most of Sweden around 2010 to positive trends during later years in parts of the country.
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| 42. |
- Östman, Örjan, et al.
(författare)
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Meta-analysis reveals top-down processes are as strong as bottom-up effects in North Atlantic coastal food webs
- 2016
-
Ingår i: Journal of Applied Ecology. - : Wiley. - 0021-8901 .- 1365-2664. ; 53:4, s. 1138-1147
-
Tidskriftsartikel (refereegranskat)abstract
- Seagrass and seaweed habitats constitute hotspots for diversity and ecosystem services in coastal ecosystems. These habitats are subject to anthropogenic pressures, of which eutrophication is one major stressor. Eutrophication favours fast-growing ephemeral algae over perennial macroalgae and seagrasses, causing habitat degradation. However, changes in top-down control, caused by, for example, overfishing, may also have negative impacts on such habitats by decreasing grazer control of ephemeral algae. Meanwhile, systematic analyses estimating top-down effects of predator manipulations across a wide range of studies are missing, limiting the potential use of top-down control measures in coastal management. Here, we review the literature on experiments that test top-down and bottom-up controls in seagrass Zostera marina and seaweed Fucus spp. food webs in the North Atlantic. Using meta-analysis and meta-regression, we compare effect sizes of consumer and nutrient manipulations on primary producers, grazers and mesopredators. Presence of mesopredators on average doubled the biomass of ephemeral algae through trophic cascades, mainly mediated via negative effects on amphipods and isopods. Of the grazers, gastropods had twice as strong a negative effect on ephemeral algae as amphipods/isopods, but responded weakly to both predators and fertilization. In accordance with theory, top-down effects became stronger with eutrophication. Across studies, top-down effects on ephemeral algae at all trophic levels are on par with eutrophication effects. However, the few studies manipulating piscivorous fish make estimates of their top-down effects uncertain. Synthesis and applications. Consistently strong top-down effects in coastal ecosystems call for an integrated ecosystem perspective. Management should consider measures to improve stocks of predatory fish and reduce mesopredators for restoration and conservation of essential seagrass and seaweed habitats, thereby increasing the long-term viability of ecosystem services from coastal habitats.
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| 43. |
- Östman, Örjan, et al.
(författare)
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Top-down control as important as nutrient enrichment for eutrophication effects in North Atlantic coastal ecosystems
- 2016
-
Ingår i: Journal of Applied Ecology. - : Wiley. - 0021-8901 .- 1365-2664. ; 53:4, s. 1138-1147
-
Forskningsöversikt (refereegranskat)abstract
- Seagrass and seaweed habitats constitute hotspots for diversity and ecosystem services in coastal ecosystems. These habitats are subject to anthropogenic pressures, of which eutrophication is one major stressor. Eutrophication favours fast-growing ephemeral algae over perennial macroalgae and seagrasses, causing habitat degradation. However, changes in top-down control, caused by, for example, overfishing, may also have negative impacts on such habitats by decreasing grazer control of ephemeral algae. Meanwhile, systematic analyses estimating top-down effects of predator manipulations across a wide range of studies are missing, limiting the potential use of top-down control measures in coastal management. Here, we review the literature on experiments that test top-down and bottom-up controls in seagrass Zostera marina and seaweed Fucus spp. food webs in the North Atlantic. Using meta-analysis and meta-regression, we compare effect sizes of consumer and nutrient manipulations on primary producers, grazers and mesopredators. Presence of mesopredators on average doubled the biomass of ephemeral algae through trophic cascades, mainly mediated via negative effects on amphipods and isopods. Of the grazers, gastropods had twice as strong a negative effect on ephemeral algae as amphipods/isopods, but responded weakly to both predators and fertilization. In accordance with theory, top-down effects became stronger with eutrophication. Across studies, top-down effects on ephemeral algae at all trophic levels are on par with eutrophication effects. However, the few studies manipulating piscivorous fish make estimates of their top-down effects uncertain.Synthesis and applications. Consistently strong top-down effects in coastal ecosystems call for an integrated ecosystem perspective. Management should consider measures to improve stocks of predatory fish and reduce mesopredators for restoration and conservation of essential seagrass and seaweed habitats, thereby increasing the long-term viability of ecosystem services from coastal habitats.
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