| 1. |
- Ahlgren, Gunnel, et al.
(författare)
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Fatty Acid Ratios in Freshwater Fish, Zooplankton and Zoobenthos - Are There Specific Optima?
- 2009
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Ingår i: Lipids in Aquatic Ecosystems. - New York : Springer-Verlag New York. - 9780387886077 - 9780387893662 ; , s. 147-178
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Two groups of polyunsaturated fatty acids (PUFA), termed omega-3 and omega-6 in food (or here as n-3 and n-6 PUFA, respectively), are essential for all vertebrates and probably also for nearly all invertebrates. The absolute concentrations of the different PUFA are important, as is an appropriate balance between the two. The optimal ratio of n-3/n-6 is not known for most organisms but is anticipated to be more or less species-specific (Sargent et al. 1995). The three most important PUFA in vertebrates are eicosapentaenoic acid (EPA, 20:5n-3), docosahexaenoic acid (DHA, 22:6n-3) and arachidonic acid (ARA, 20:4n-6). Both EPA and ARA are precursors for biologically active eicosanoids that are vital components of cell membranes and play many dynamic roles in mediating and controlling a wide array of cellular activities (Crawford et al. 1989; Harrison 1990; Henderson et al. 1996; see Chap. 9). Since n-3 and n-6 PUFA cannot be synthesized de novo by most metazoans, they must be included in the diet, either as EPA, DHA and ARA, or as their precursors, such as α-linolenic acid (ALA, 18:3n-3, precursor of EPA and DHA) and linoleic acid (LIN, 18:2n-6, precursor of ARA) (Bell et al. 1986; Sargent et al. 1995). Both ALA and LIN are produced in the thylacoid membranes of algae and plants with chlorophyll (Sargent at al. 1987).
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| 2. |
- Bergfur, Jenny, et al.
(författare)
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Effects of nutrient enrichment on C and N stable isotope ratios of invertebrates, fish and their food resources in boreal streams
- 2009
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Ingår i: Hydrobiologia. - : Springer. - 0018-8158 .- 1573-5117. ; 628, s. 67-79
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Tidskriftsartikel (refereegranskat)abstract
- Carbon and nitrogen stable isotopes are frequently used to study energy sources and food web structure in ecosystems, and more recently, to study the effects of anthropogenic stress on aquatic ecosystems. We investigated the effect of nutrient enrichment on d13C and d15N in fine (FPOM), coarse (CPOM) particulate organic matter, periphyton, invertebrates and fish in nine boreal streams in south-central Sweden. In addition, we analysed the diet of benthic consumers using stable isotope data. Increases in d15N of periphyton (R2 = 0.88), CPOM (0.78), invertebrates (0.92) and fish (0.89) were related to nutrient enrichment. In contrast, d13C signatures did not change along the nutrient gradient. Our results show that d15N has potential as a sensitive indicator of nutrient enrichment in boreal streams. Carbon and nitrogen isotopes failed to elucidate putative diets of selected aquatic consumers. Indeed, comparison of low- and high-impact sites showed that d13C of many consumers were found outside the ranges of basal resource d13C. Moreover, ranges of basal resource d13C and d15N overlapped at both low and high sites, making discrimination between the importance of allochthonous and autochthonous production difficult. Our findings show that a fractionation rate of 3.4% is not always be appropriate to assess trophic interactions, suggesting that more studies are needed on fractionation rates along gradients of impairment.
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| 3. |
- Fischer, Helmut, et al.
(författare)
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Microbial leaf degraders in boreal streams : bringing together stochastic and deterministic regulators of community composition
- 2009
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Ingår i: Freshwater Biology. - : Wiley. - 0046-5070 .- 1365-2427. ; 54:11, s. 2276-2289
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Tidskriftsartikel (refereegranskat)abstract
- Leaves that fall into the water represent a new habitat for microorganisms to colonise in streams, providing an opportunity to study colonisation and the subsequent regulation of community structure. We explored community composition of bacteria and fungi on decomposing alder leaves in nine streams in central Sweden, and describe their relationship with environmental variables. Succession of the microbial community was studied in one of the streams for 118 days. Microbial community composition was examined by denaturing gradient gel electrophoresis on replicate samples of leaves from each stream. 2. During succession in one stream, maximum taxon richness was reached after 34 days for bacteria and 20 days for fungi respectively. Replicate samples within this stream differed between each other earlier in colonisation, while subsequently such variation among replicate communities was low and remained stable for several weeks. Replicate samples taken from all the nine streams after 34 days of succession showed striking similarities in microbial communities within-streams, although communities differed more strongly between streams. 3. Canonical analysis of microbial communities and environmental variables revealed that water chemistry had a significant influence on community composition. This influence was superimposed on a statistical relationship between the properties of stream catchments and microbial community composition. 4. The catchment regulates microbial communities in two different ways. It harbours the species pool from which the in-stream microbial community is drawn and it governs stream chemistry and the composition of organic substrates that further shape the communities. We suggest that there is a random element to colonisation early in succession, whereas other factors such as species interactions, stream chemistry and organic substrate properties, result in a more deterministic regulation of communities during later stages.
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| 4. |
- Fölster, Jens, et al.
(författare)
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A Novel Environmental Quality Criterion for Acidification in Swedish Lakes - An Application of Studies on the Relationship Between Biota and Water Chemistry
- 2007
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Ingår i: Acid Rain - Deposition to Recovery. - Netherlands : Springer. - 9781402058844 ; , s. 331-338
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The recovery from acidification has led to the demand for more precise criteria for classification of acidification. The Swedish Environmental Protection Agency has revised Sweden's Ecological Quality Criteria for acidification to improve the correlation between the chemical acidification criteria and biological effects. This paper summarises the most relevant findings from several of the studies commissioned for this revision. The studies included data on water chemistry in 74 reference lakes in southern Sweden with data on fish in 61 of the lakes, as well as data on littoral fauna in 48 lakes. We found that the acidity variable most strongly correlated to the biota was the median pH from the current year. Our results probably do not reflect the mechanisms behind the negative effects of acidity on the biota, but are fully relevant for evaluation of monitoring data. The biogeochemical models used for predicting acidification reference conditions generate a pre-industrial buffering capacity. In order to get an ecologically more relevant criteria for acidification based on pH, we transferred the estimated change in buffering capacity into a corresponding change in pH. A change of 0.4 units was defined as the threshold for acidification. With this criterion a considerably lower number of Swedish lakes were classified as acidified when compared with the present Ecological Quality Criteria.
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| 5. |
- Fölster, Jens, et al.
(författare)
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A Novel Environmental Quality Criterion for Acidification in Swedish Lakes – An Application of Studies on the Relationship Between Biota and Water Chemistry
- 2007
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Ingår i: Water, Air, & Soil Pollution: Focus. - : Springer Science and Business Media LLC. - 1567-7230 .- 1573-2940. ; 7:1-3, s. 331-338
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Tidskriftsartikel (refereegranskat)abstract
- The recovery from acidification has led to the demand for more precise criteria for classification of acidification. The Swedish Environmental Protection Agency has revised Sweden’s Ecological Quality Criteria for acidification to improve the correlation between the chemical acidification criteria and biological effects. This paper summarises the most relevant findings from several of the studies commissioned for this revision. The studies included data on water chemistry in 74 reference lakes in southern Sweden with data on fish in 61 of the lakes, as well as data on littoral fauna in 48 lakes. We found that the acidity variable most strongly correlated to the biota was the median pH from the current year. Our results probably do not reflect the mechanisms behind the negative effects of acidity on the biota, but are fully relevant for evaluation of monitoring data. The biogeochemical models used for predicting acidification reference conditions generate a pre-industrial buffering capacity. In order to get an ecologically more relevant criteria for acidification based on pH, we transferred the estimated change in buffering capacity into a corresponding change in pH. A change of 0.4 units was defined as the threshold for acidification. With this criterion a considerably lower number of Swedish lakes were classified as acidified when compared with the present Ecological Quality Criteria.
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| 6. |
- Goedkoop, Willem, et al.
(författare)
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Biologisk karaktärisering av bäckar i typområden jordbruksmark
- 2009
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Projektet (kontraktnr. 222 0742) omfattar standardiserad provtagning av fastsittande kiselalger, bottenfauna och fisk (elfiske), taxonomiska analys och bedömning med nya bedömningsgrunderna för dessa kvalitetsfaktorer för vattendragen i typområden jordbruksmark (8 intensivområden). Även en bedömning av vattenkemi ingår i uppdraget. Syftet med uppdraget är att genom analys av påväxtalger, bottenfauna och fisksamhället och en bedömning med nya bedömningsgrunder för miljökvalitet göra en karaktärisering och analys av ekologisk status för vattendragen i typområden jordbruksmark (8 intensivområden).
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| 7. |
- Naddafi, Rahmat, 1975-
(författare)
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The Invasion of the Zebra Mussel - Effects on Phytoplankton Community Structure and Ecosystem Function
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Biological invasion has become a major threat to economy, ecology, global biodiversity and ecosystem function of aquatic ecosystems. The main aim of the thesis was to study the effects of the zebra mussel (Dreissena polymorpha), a versatile invasive species, on phytoplankton dynamics and ecosystem function of lakes.In a first attempt, I compared the density of Dreissena and the physicochemical data of ecosystems that it invaded among North American and European lakes to identify important factors in its invasion success. Secondly, I investigated the impact of zebra mussels on phytoplankton community composition in a natural lake. Thirdly, I evaluated whether zebra mussel feeding behavior were affected by the presence of predatory waterborne cues. Finally, I examined the effect of Dreissena on seston stoichiometry.A Generalized Additive Model revealed that a joint effect of surface area, mean depth, total phosphorus and calcium concentrations can explain the variability in Dreissena density. Selective grazing by zebra mussels varied in relation to seasonal phytoplankton dynamics. Risk cues released by predators affected both feeding rate and prey selection of the mussels and had cascading indirect effects on phytoplankton biomass and community structure. I found that the flux in nutrients caused by differences in zebra mussel consumption lead to a variation in phytoplankton nutrient limitation.The flexibility of zebra mussel feeding behavior and variation in susceptibility among phytoplankton groups to mussel ingestion indicate that invading zebra mussels could alter phytoplankton community composition of lakes and have important ecosystem consequences. The results of this thesis contribute to the growing evidence that predators indirectly affect resource dynamics and food web structure through their non-lethal effects on consumers. The results suggested that zebra mussel can indirectly both reduce and increase the energy transfer efficiency from primary producers to upper trophic levels in the pelagic and benthic food webs, respectively.
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| 8. |
- Widenfalk, Anneli, et al.
(författare)
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Effects of pesticides on community composition and activity of sediment microbes : responses at various levels of microbial community organization
- 2008
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Ingår i: Environmental Pollution. - : Elsevier BV. - 0269-7491 .- 1873-6424. ; 152:3, s. 576-584
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Tidskriftsartikel (refereegranskat)abstract
- A freshwater sediment was exposed to the pesticides captan, glyphosate, isoproturon, and pirimicarb at environmentally relevant and high concentrations. Effects on sediment microorganisms were studied by measuring bacterial activity, fungal and total microbial biomass as community-level endpoints. At the sub-community level, microbial community structure was analysed (PLFA composition and bacterial 16S rRNA genotyping, T-RFLP). Community-level endpoints were not affected by pesticide exposure. At lower levels of microbial community organization, however, molecular methods revealed treatment-induced changes in community composition. Captan and glyphosate exposure caused significant shifts in bacterial community composition (as T-RFLP) at environmentally relevant concentrations. Furthermore, differences in microbial community composition among pesticide treatments were found, indicating that test compounds and exposure concentrations induced multidirectional shifts. Our study showed that community-level end points failed to detect these changes, underpinning the need for application of molecular techniques in aquatic ecotoxicology.
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