| 1. |
- Angeler, David, et al.
(author)
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Biological responses to liming in boreal lakes: an assessment using plankton, macroinvertebrate and fish communities
- 2010
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In: Journal of Applied Ecology. - : Wiley. - 0021-8901 .- 1365-2664. ; 47, s. 478-486
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Journal article (peer-reviewed)abstract
- P>1. Biological responses to liming of acidified surface waters are equivocal and limit the overall assessment of food web responses. In this study, we analysed community structure in limed, acidified and circumneutral lakes, based on the analyses of phytoplankton, zooplankton, macroinvertebrates (littoral, sublittoral, profundal) and fish between 2000 and 2004. We also studied associations between functional feeding groups in food webs.2. Most univariate metrics of structure and function revealed similar community attributes among lake types, suggesting that community responses to natural recovery from acidification and liming management converge with those observed in circumneutral lakes. These trends were less clear in the multivariate analyses which showed significant community differences among lake types. For phytoplankton, these patterns were partly mediated by the invasive raphidophycean flagellate Gonyostomum semen.3. The associations between functional feeding groups indicated less connectivity and food web complexity in limed lakes relative to the other lake types. We speculate that repeated lime applications comprise frequent pulse disturbances which offset the establishment of stable trophic relationships in the food webs of limed lakes.4. Synthesis and applications. The limited structural and functional food web similarity among lake types supports the argument that liming constitutes an ecosystem-level disturbance. Managers should be aware of the ecosystem impacts of altered disturbance regimes when designing their management schemes because this can influence the success of restoration programmes. Furthermore, the lack of recovery, mediated in part by species invasions, suggests that impacts derived from global change are likely to lead to novel environmental situations. This calls for adaptive management strategies where managers are challenged to tackle multiple forms of anthropogenic stress simultaneously.
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| 2. |
- Angeler, David, et al.
(author)
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Identifying resilience mechanisms to recurrent ecosystem perturbations
- 2010
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In: Oecologia. - : Springer Science and Business Media LLC. - 0029-8549 .- 1432-1939. ; 164, s. 231-241
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Journal article (peer-reviewed)abstract
- The complex nature of ecological systems limits the unambiguous determination of mechanisms that drive resilience to natural disturbance or anthropogenic stress. Using eight-year time series data from boreal lakes with and without bloom formation of an invasive alga (Gonyostomum semen, Raphidophyceae), we studied resilience of phytoplankton communities in relation to recurring bloom impacts. We first characterized phytoplankton community dynamics in both lake types using univariate metrics of community structure (evenness, species richness, biovolume and Simpson diversity). All metrics, except species richness, were substantially altered and showed an inherent stronger variability in bloom lakes relative to reference lakes. We assessed resilience mechanisms using a multivariate time series modelling technique. The models captured clear successional dynamics of the phytoplankton communities in all lakes, whereby different groups of species were substituted sequentially over the ice-free period. The models also identified that G. semen impacts in bloom lakes were only manifested within a single species group, not across species groups, highlighting the rapid renewal of the phytoplankton communities upon bloom collapse. These results provide empirical support of the cross-scale resilience model. Cross-scale resilience could provide an explanation for the paradox that similar species richnesses are seen in bloom-forming lakes and reference lakes despite the clear difference between the community features of the two different sets of lakes investigated.
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| 3. |
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| 4. |
- Bundschuh, Mirco, et al.
(author)
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Evaluation of pesticide monitoring strategies in agricultural streams based on the toxic-unit concept - Experiences from long-term measurements
- 2014
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In: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 484, s. 84-91
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Journal article (peer-reviewed)abstract
- The European Water Framework Directive requires surface water bodies to have a good chemical and ecological status. Although relatively few pesticides are included in the list of priority pollutants, they pose, due to their intrinsic biological activity, a significant risk for the integrity of aquatic ecosystems. In this context, the pesticide (up to 128 pesticides including some transformation products) exposure pattern in four agricultural streams and two rivers was determined from 2002 to 2011 under the umbrella of the Swedish national monitoring program employing time-proportional and grab sampling strategies, respectively. After transforming the measured pesticide concentrations into toxic units, the European Uniform Principles for algae (chronic), invertebrates and fish (both acute), which are partly employed as benchmark for pesticide regulation, were only occasionally (<2%) exceeded. Moreover, this evaluation showed no long-term trends over the years. However, recent publications suggested that those thresholds are not protective for ecosystem structure and function, indicating a risk of up to 20% and 35% of the samples from the agricultural streams and the rivers, respectively. Moreover, the monitoring data show a continuous but rather low toxic potential of pesticides for all three trophic levels throughout the year, which suggests pesticides as an evolutionary force in agriculturally impacted aquatic ecosystems. However, the flow-triggered sampling, which was implemented as an additional sampling strategy in one of the agricultural streams starting in 2006, displayed an up to 7-fold underestimation of the maximum concentration in terms of toxic units for daphnids and fish during run-off events. The present study thus underpins that the optimal sampling design for pesticide monitoring strongly depends on its overall purpose. If the long-term exposure pattern is of concern a time-proportional composite sampling strategy is recommended, while for an assessment of peak exposures a flow-event-triggered high-resolution sampling strategy is superior. (C) 2014 Elsevier B.V. All rights reserved.
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| 5. |
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| 6. |
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| 7. |
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| 8. |
- Goedkoop, Willem
(author)
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Distinguishing the effects of habitat degradation and pesticide stress on benthic invertebrates using stressor-specific metrics
- 2013
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In: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 444, s. 480-490
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Journal article (peer-reviewed)abstract
- Hydromorphological degradation is a well known stressor for running waters, while the effects of elevated levels of pesticides are widely ignored. Hence, distinguishing between the effects of these two stressors is an urgent task for water managers that aim at appropriate remediation measures. We used a large monitoring data set on benthic invertebrates, habitat descriptors, and physico-chemical variables to develop the SPEAR[%](habitat) metric that indicates the effects of in-stream habitat degradation. SPEAR[%](habitat) correlated significantly with the habitat degradation score (HDS; based on substratum and vegetation coverage), while it did not respond to any physico-chemical variables (r(2)=0.20). This relationship improved for streams with low modeled pesticide inputs (r(2)=033), and improved even further for a subset of streams dominated by soft-bottom substrata, i.e. for similar stream-types (r(2)=0.65). These relationships were confirmed for an independent dataset that was not used in the derivation of the HDS (r(2)=0.57 and r(2)=0.65, respectively). These findings show that the SPEAR[%](habitat) had a high degree of specificity for the effects of habitat degradation. Conversely, neither the commonly used EPT and ASPT metrics, nor the German Fauna Index or SPEAR[%](pesticides) showed significant relationships with HDS. These metrics instead correlated significantly with the run-off potential (RP), a proxy of pesticide contamination of streams. Similarly, RP was also the most important explanatory variable for SPEAR[%](pesticides), followed by alkalinity and the number of forested upstream stretches (r(2)=0.61). The latter are expected to alleviate pesticide effects, as indicated by higher SPEAR[%](pesticides) values. These findings show that an integrated analysis of the two stressor-specific SPEAR-metrics in combination with the metrics of general ecological degradation can help water managers to distinguish between the effects of habitat degradation and pesticide stress, two co-occurring stressors in agricultural landscapes. (C) 2012 Elsevier B.V. All rights reserved.
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| 9. |
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| 10. |
- Goedkoop, Willem, et al.
(author)
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Retention of N and P by zebra mussels (Dreissena polymorpha Pallas) and its quantitative role in the nutrient budget of eutrophic Lake Ekoln, Sweden
- 2011
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In: Biological Invasions. - : Springer Science and Business Media LLC. - 1387-3547 .- 1573-1464. ; 13, s. 1077-1086
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Journal article (peer-reviewed)abstract
- We quantified cover, population densities, size distribution and biomass of zebra mussels along 7 transects in eutrophic Lake Ekoln (Sweden). We also analyzed the elemental (C, N, P) composition of zebra mussel soft tissue and computed their retention rates of N and P their quantitative role in the lake's nutrient budget. We hypothesized that zebra mussels play an important role in the nutrient budget of the lake and speculate that the successive harvesting of cultured mussels could contribute to the lake's rate of recovery from cultural eutrophication. At depths exceeding 5 m, mussels covered consistently less than 5% or were absent. Similarly, mean densities were 3,158 +/- A 2,143 ind m(-2) between 2 and 4 m, but rapidly declined at larger depths. Calculated clearance rates averaged 19.4 +/- A 2.3 km(3) y(-1), implying the entire lake is filtered every 8-10 days. Concentrations of N and P in mussel soft tissue averaged 100.9 +/- A 1.5 mg N g(-1) DW and 9.3 +/- A 0.2 mg P g(-1) DW. The lake population was estimated to 22.2 +/- A 2.6 x 10(10) mussels, corresponding to a standing stock biomass of 362 +/- A 42 ton DW, or conservative estimates of 36.6 +/- A 4.3 ton N and 3.4 +/- A 0.4 ton P. Assuming a life span of 2-3 years gives a retention estimate of 1.2-1.8 ton P y(-1) by mussels, corresponding to 50-77% of the annual P influx from Uppsala sewage treatment plant to the lake. Similarly, annual N-retention by zebra mussels makes up 13-20 ton N y(-1), largely equaling the annual N-deposition from atmospheric sources on the lake's surface. These retention rates correspond to only a few percent of the annual P-load from agricultural sources, but we argue that the quantitative role of zebra mussels in nutrient budgets is much larger if these budgets are adjusted for the bias introduced by coarse estimates of N and P pools that include a large share of refractory P.
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| 11. |
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| 12. |
- Goedkoop, Willem, et al.
(author)
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Sublethal and sex-specific cypermethrin effects in toxicity tests with the midge Chironomus riparius Meigen
- 2010
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In: Ecotoxicology. - : Springer Science and Business Media LLC. - 0963-9292 .- 1573-3017. ; 19, s. 1201-1208
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Journal article (peer-reviewed)abstract
- We quantified sublethal and sex-specific cypermethrin effects in experiments (29 days) with the midge Chironomus riparius at different levels of sediment organic matter content (0, 5, and 20%). We found highly significant effects of cypermethrin concentrations and sediment type on emergence, mean development rate, and adult size. For example, emergence/survival rates were 70-100% below 0.8 mu g/l and unaffected by organic matter content. At 3.2 mu g/l, however, no larvae survived in sediment without organic matter, but survival successively increased to 26 +/- 11% in sediment with 20% organic matter. Mean development rates were always higher for males than for females, and significant differences between sexes occurred consistently in controls and in treatments with our lowest concentration of 0.05 mu g/l. Sex-specific differences in mean development rate decreased across the cypermethrin gradient, suggesting that male development was affected more than that of females at similar concentrations. We also found an increase in adult size across the concentration gradient in sediments lacking organic matter and suggest an increased feeding activity due to sublethal toxic stress as a probable causal mechanism. We speculate that the observed sex-specific effects on development rates and adult size can have strong repercussions on emergence timing and fecundity, respectively.
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| 13. |
- Goedkoop, Willem
(author)
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Traits-based approaches in bioassessment and ecological risk assessment: Strengths weaknesses, opportunities and threats
- 2011
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In: Integrated Environmental Assessment and Management. - : Wiley. - 1551-3777 .- 1551-3793. ; 7, s. 198-208
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Journal article (peer-reviewed)abstract
- We discuss the application of traits-based bioassessment approaches in retrospective bioassessment as well as in prospective ecological risk assessments in regulatory frameworks. Both approaches address the interaction between species and stressors and their consequences at different levels of biological organization, but the fact that a specific species may be less abundant in a potentially impacted site compared with a reference site is, regrettably, insufficient to provide diagnostic information. Species traits may, however, overcome the problems associated with taxonomy-based bioassessment. Trait-based approaches could provide signals regarding what environmental factors may be responsible for the impairment and, thereby, provide causal insight into the interaction between species and stressors. For development of traits-based (TBA), traits should correspond to specific types of stressors or suites of stressors. In this paper, a strengths, weaknesses, opportunities, and threats (SWOT) analysis of TBA in both applications was used to identify challenges and potentials. This paper is part of a series describing the output of the TERA (Traits-based ecological risk assessment: Realising the potential of ecoinformatics approaches in ecotoxicology) Workshop held between 7 and 11 September, 2009, in Burlington, Ontario, Canada. The recognized strengths were that traits are transferrable across geographies, add mechanistic and diagnostic knowledge, require no new sampling methodology, have an old tradition, and can supplement taxonomic analysis. Weaknesses include autocorrelation, redundancy, and inability to protect biodiversity directly. Automated image analysis, combined with genetic and biotechnology tools and improved data analysis to solve autocorrelation problems were identified as opportunities, whereas low availability of trait data, their transferability, their quantitative interpretation, the risk of developing nonrelevant traits, low quality of historic databases, and their standardization were listed as threats
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| 14. |
- Hallstan, Simon, et al.
(author)
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Current and modeled potential distribution of the zebra mussel (Dreissena polymorpha) in Sweden
- 2010
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In: Biological Invasions. - : Springer Science and Business Media LLC. - 1387-3547 .- 1573-1464. ; 12, s. 285-296
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Journal article (peer-reviewed)abstract
- In this study, we report the results from a recently performed survey of zebra mussel in Sweden and present a risk model for the potential distribution of the species. The zebra mussel was found in 11 of the 30 surveyed lakes and rivers. Most of the observations were made in the north-eastern parts of Lake Malaren, i.e., in the basins Ekoln, Skarven, and Gorvaln. Hierarchical partitioning and stepwise selection of water chemistry variables in a multiple logistic model identified pH and magnesium concentrations as the best predictors for zebra mussel occurrence. We conjecture that magnesium is an important predictor due to its crucial role in mussel physiology. The logistic model was applied on 2,781 lakes and in total 109 lakes (3.9%), most of them situated in specific areas in central Sweden, in the very south and on the island of Gotland, were predicted to be potentially at risk for zebra mussel invasions. The lakes potentially at risk for zebra mussel invasions are separated by the soft-water boreal lakes that constitute the vast majority of lakes on the Fennoscandian peninsula, thus forming barriers for further dispersal.
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| 15. |
- Hancke, Marnie, et al.
(author)
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Genetic diversity of Monoporeia affinis in relationship to environmental and spatial factors in Sweden’s largest lakes
- 2012
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In: Fundamental and Applied Limnology. - : Schweizerbart. - 1863-9135. ; 181, s. 183–195-
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Journal article (peer-reviewed)abstract
- The glacial relict species Monoporeia affinis undergoes pronounced population fluctuations in Sweden's three largest lakes, which may be due to multiple forms of environmental stress, including eutrophication and subsequent hypoxia. In this study, we use cytochrome c oxidase subunit I (COI) and 16srRNA (16 S) sequence data to assess the genetic diversity of this freshwater amphipod, and study their spatial and environmental correlates. The populations in the three lakes were genetically differentiated with haplotype diversity of the 16 S gene being lower in populations from Lake Malaren compared to those in Lake Vattern and Lake Vanern; however, a broad-scale spatial analysis did not detect significant spatial patterns in genetic diversity across the lakes. Within lakes, however, subtle spatial effects were detected in the form of a significant distance decay of genetic diversity in some lakes, highlighting the importance of considering different spatial scales for studying genetic diversity. From the environmental variables studied, a biologically relevant impact of both oxygen and total phosphorus levels on haplotype diversity levels was found, indicating the negative consequences of eutrophication on genetic diversity of M. affinis. Despite significant decreases and fluctuations in population sizes, the demographic history of M. affinis populations is best described by a model of constant population size over time, suggesting a sufficiently large effective population size.
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| 16. |
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| 17. |
- Lau, Danny C P, et al.
(author)
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Autochthonous resources are the main driver of consumer production in dystrophic boreal lakes
- 2014
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In: Ecology. - : Wiley. - 0012-9658 .- 1939-9170. ; 95, s. 1506-1519
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Journal article (peer-reviewed)abstract
- Dystrophic lakes are widespread in temperate regions and intimately interact with surrounding terrestrial ecosystems in energy and nutrient dynamics, yet the relative importance of autochthonous and allochthonous resources to consumer production in dystrophic lakes remains controversial. We argue that allochthonous organic matter quantitatively dominates over photosynthetic autotrophs in dystrophic lakes, but that autotrophs are higher in diet quality and more important for consumers as they contain essential polyunsaturated fatty acids (PUFA). In a field study, we tested the hypotheses that (1) autochthonous primary production is the main driver for consumer production, despite being limited by light availability and low nutrient supplies, and greater supply of allochthonous carbon, (2) the relative contribution of autotrophs to consumers is directly related to their tissue PUFA concentrations, and (3) methane-oxidizing bacteria (MOB) provide an energy alternative for consumers.Pelagic and benthic consumer taxa representing different trophic levels were sampled from five dystrophic lakes: isopod Asellus aquaticus, megalopteran Sialis lutaria, dipteran Chaoborus flavicans, and perch Perca fluviatilis. Based on carbon and nitrogen stable isotopes, the relative contributions of autochthonous (biofilms and seston) and allochthonous (coarse particulate and dissolved organic matter) resources and MOB to these taxa were 47-79%, 9-44% and 7-12% respectively. Results from fatty acid (FA) analyses show that the relative omega 3-FA and PUFA concentrations increased with trophic level (Asellus < Sialis and Chaoborus < Perca). Also, eicosapentaenoic-acid (EPA), omega 3-FA and PUFA concentrations increased with the autochthonous contribution in consumers, i.e., a 47-79% biofilm and/or seston diet resulted in tissue EPA of 4.2-18.4, omega 3 FAs of 11.6-37.0 and PUFA of 21.6-61.0 mg/g dry mass. The results indicate that consumers in dystrophic lakes predominantly rely on energy from autotrophs and that their PUFA concentrations are dependent on the relative contribution of these autochthonous resources. The limited energy support from MOB suggests they are not negligible and are potentially an integral part of the food webs. Our findings show that autochthonous resources are the main driver of secondary production even in dystrophic lakes and offer new insights into the functioning of these ecosystems.
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| 18. |
- Lau, Danny C P, et al.
(author)
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Cross-ecosystem differences in lipid composition and growth limitation of a benthic generalist consumer
- 2013
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In: Limnology and Oceanography. - : Wiley. - 0024-3590 .- 1939-5590. ; 58, s. 1149-1164
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Journal article (peer-reviewed)abstract
- In a field study, we analyzed the fatty acid (FA) composition of the benthic generalist Asellus aquaticus collected from boreal lakes, ponds, and streams across gradients in ambient nutrient levels. In laboratory feeding experiments, we tested the diet-quality and seasonal effects on somatic growth and FAs of spring-and autumn-collected Asellus that were fed four different diets containing increasing concentrations of polyunsaturated FAs (PUFA): conditioned leaf litter, algal flakes, mixed litter and algal flakes (Mixed), or Mixed plus fish-food flakes. Ambient nutrients were strong determinants of FA variation of field Asellus, explaining > 44% in total. The ratios of eicosapentaenoic acid (EPA) to total FAs, EPA: omega 3, and omega 3 : omega 6 of Asellus increased up to four times with increasing trophic state and decreasing humic matter content, likely because dietary omega 3 FAs were more prevalent in benthic habitats of eutrophic than of oligotrophic systems. In the feeding trials, growth of Asellus collected in both seasons was markedly lower on leaf litter than on higher PUFA diets. However, autumn-collected Asellus fed a Mixed or Mixed+fish-food diet grew 3-10 times faster, but retained < 50% EPA and PUFA than spring counterparts. Asellus optimized PUFA accumulation in spring but somatic growth in autumn. Our field survey suggests ambient nutrient concentrations modify dietary PUFA supply from basal resources, while laboratory studies show that growth response and PUFA accumulation of Asellus differ between seasons, likely due to its season-specific physiological status and diet quality. An increase in nutrients will release benthic consumers from growth limitation and favor more efficient trophic transfer.
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| 19. |
- Lau, Danny C P, et al.
(author)
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Fatty acid composition of consumers in boreal lakes - variation across species, space and time
- 2012
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In: Freshwater Biology. - : Wiley. - 0046-5070 .- 1365-2427. ; 57, s. 24-38
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Journal article (peer-reviewed)abstract
- 1. Fatty acids (FAs) have been widely applied as trophic biomarkers in aquatic food web studies. However, current knowledge of inter- and intraspecific variation in consumer FA compositions across spatial and temporal scales is constrained to a few pelagic taxa.
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| 20. |
- Lundqvist, Anna, et al.
(author)
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Effects of extracellular polymeric and humic substances on chlorpyrifos bioavailability to Chironomus riparius
- 2010
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In: Ecotoxicology. - : Springer Science and Business Media LLC. - 0963-9292 .- 1573-3017. ; 19:4, s. 614-622
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Journal article (peer-reviewed)abstract
- The role of sediment organic matter quality and quantity for chlorpyrifos bioavailability was studied in experiments with Chironomus riparius larvae and with four types of organic matter; (1) commercially available extracellular polymeric substances (EPS), (2) EPS produced by sediment microbes, (3) commercially available humic substances and, (4) humic substances extracted from a boreal lake. The effects of each type of organic matter were assessed at three concentrations. We used a C-14-tracer approach to quantify uptake of chlorpyrifos in the larvae, and the partitioning of the insecticide within the microcosm. Carbon-normalised larval uptake was reduced both by EPS and humic substances. However, the reduction in uptake was much greater for EPS than for humic substances: uptake was reduced by 94 and 88% for commercial and complex EPS, and by 59 and 57% for commercial and complex humic substances, respectively. We also found differences in chlorpyrifos uptake, and sediment concentrations between treatments with commercially available and complex polymers, suggesting that minor differences in the quality of relatively simple organic molecules can affect contaminant behaviour in ecotoxicological studies. Passive uptake in dead controls was 40% of that in living larvae. Therefore, both passive and digestive uptake were important processes for chlorpyrifos uptake by larvae. Our results show that both EPS and humic substances affect chlorpyrifos bioavailability to sediment biota negatively and contribute to the understanding of the processes that regulate organic contaminant bioavailability in aquatic environments.
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| 21. |
- Lundqvist, Anna, et al.
(author)
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Interactions with DOM and biofilms affect the fate and bioavailability of insecticides to invertebrate grazers
- 2012
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In: Ecotoxicology. - : Springer Science and Business Media LLC. - 0963-9292 .- 1573-3017. ; 21:8, s. 2398-2408
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Journal article (peer-reviewed)abstract
- We studied the fate and bioavailability of insecticides in short-term experiments (48 h) with different hydrophobicity (3.8 pM carbofuran, 3.0 pM lindane, and 5.3 pM chlorpyrifos) across gradients in dissolved organic matter (low-, medium-, and high-DOM) in freshwater microcosms, mimicking runoff events of pesticides. The effects of biofilms were studied by including treatments with biofilms cultivated under different DOM-concentrations. The presence of biofilms negatively affected chlorpyrifos water concentrations, indicating rapid sorption of this hydrophobic pesticide, while lindane concentrations instead increased and carbofuran concentrations were unaffected. Associations of lindane and chlorpyrifos with biofilms were 1.6-2.0 times higher in low- and high-DOM than in medium-DOM treatments, indicating that sorption was affected not only by the quantity, but also by the quality of DOM. Although the proportion of pesticides recovered in biofilms was consistently less than 1 % of added pesticide, pesticide concentrations in biofilms were on average more than 75- (carbofuran) and 382-times (lindane) higher than those in water. Snail accumulation of all three pesticides was significantly affected by DOMconcentrations and correlated to pesticide hydrophobicity, but the relationships were not straightforward. For example, carbofuran uptake in treatments without biofilms was higher in low-DOM than in medium- and high-DOM treatments, while chlorpyrifos uptake instead increased across the DOM-gradient. Biofilms played a role only for the uptake of chlorpyrifos, which decreased markedly in the presence of biofilms. Bioconcentration factors (BCF) calculated for snails and biofilms differed for the three pesticides and were related to their sorption behaviour (i.e., hydrophobicity). The relative proportion of pesticide uptake through biofilm consumption was consistently less than 2 %, showing that passive uptake was by far the predominant uptake pathway for all three pesticides.
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| 22. |
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| 23. |
- Naddafi, Rahmat, et al.
(author)
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Variation in tissue stoichiometry and condition index of zebra mussels in invaded Swedish lakes
- 2012
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In: Biological Invasions. - : Springer Science and Business Media LLC. - 1387-3547 .- 1573-1464. ; 14:10, s. 2117-2131
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Journal article (peer-reviewed)abstract
- We examined the spatial variation in carbon:nitrogen:phosphorus (C:N:P) stoichiometry and condition index of the zebra mussel (Dreissena polymorpha), non-indigenous species, in four Swedish lakes with different productivity. Within-lake variability was observed in tissue C:N molar ratios of Dreissena in all lakes and in tissue C:P ratio only in three lakes. Depth had no effect on tissue C:P and N:P ratios of Dreissena. A positive correlation was found between C:N:P stoichiometry of seston and elemental composition of zebra mussel in one of the lakes. Tissue C:N and N:P ratios were the main factors that related to zebra mussel condition index. Zebra mussel condition was positively related to tissue C:N ratio. Smaller Dreissena had higher C:N ratio than larger Dreissena in two of the four lakes. Zebra mussels in the lake with highest productivity had lower C:P and N:P ratios than zebra mussels in the lake with lowest productivity. Our study suggests that the zebra mussel may modify their phosphorus content in relation to lake trophic state, and therefore cope with stoichiometric constraints which may explain the invasion success of this and other related species.
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| 24. |
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| 25. |
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