11 results on '"Wiberg-Larsen, Peter"'
Search Results
2. The effect of partial and total drought on the macroinvertebrate communities of three small Danish streams
- Author
-
Iversen, Torbert Moth, Wiberg-Larsen, Peter, Hansen, Søren Birkholm, and Hansen, Frode S.
- Published
- 1978
- Full Text
- View/download PDF
3. Impact of pesticides on hyphomycetes leaf processing and macroinvertebrate shredding activity
- Author
-
Juul Monberg, Rikke, Rasmussen, Jes, Baatrup-Pedersen, Annette, Wiberg-Larsen, Peter, and Brodersen, Klaus Peter
- Subjects
Macroinvertebrates ,Shredding activity ,Binary mixture ,Microbial processing - Abstract
Pesticides are frequently applied in agricultural catchments and subsequently transported to stream recipients through e.g. tile drainage and surface runoff. This gives rise to short pulses of pesticide contamination in the stream, where lipophilic compounds rapidly adsorb to organic matter, consequently impacting stream dwelling organism feeding on the organic material.The impact of pyrethroid insecticides on stream macroinvertebrates are well studied and increased mortality and drift rate along with decreased feeding activity are well known responses to even very low concentrations (10-100 ng/L). However, the potential impact of pesticides on aquatic microbes is probably equally important. Microbial organisms are essential in organic matter breakdown, and their growth additionally increases the food quality of organic matter for macroinvertebrates. Consequently, pesticides impacting microbial organisms have the power to reduce organic matter breakdown and food quality for macroinvertebrates, thereby decreasing ecosystem decomposition rates. We exposed preconditioned leafs of beech (Fagus sylvatica) to the fungicide propiconazole (100, 1000 or 2000 μg/L) and/or the insecticide alpha-cypermethrine (100, 1000 or 2000 ng/L) for three hours. Subsequently, we studied post exposure leaf degradation for four weeks in the laboratory in the presence/absence of two macroinvertebrate shredders (Gammarus pulex and Halesus radiatus) applying a classic crossed factorial design. Preliminary results indicate decreasing microbial litter processing with increasing concentrations of either propiconazole or alpha-cypermethrine. Additionally, the binary mixture further reduced microbial litter processing compared to single compound exposures. A similar reduction in leaf litter processing was only evident during the first post exposure week when macroinvertebrate shredders were present. After four weeks no differences were apparent among treatments indicating a strong degree of functional redundancy applying this macroinvertebrate assemblage.
- Published
- 2009
4. Environmental and spatial controls of taxonomic versus trait composition of stream biota.
- Author
-
Göthe, Emma, Baattrup‐Pedersen, Annette, Wiberg‐Larsen, Peter, Graeber, Daniel, Kristensen, Esben A., and Friberg, Nikolai
- Subjects
INVERTEBRATES ,MACROPHYTES ,BIOTIC communities ,FRESHWATER ecology ,ECOSYSTEMS - Abstract
The spatial organisation of biotic communities derives from factors operating at a wide range of spatial and temporal scales. Despite strong scientific evidence of prevalent spatial control of community composition in freshwater ecosystems, local environmental factors are often considered as the main drivers of community change. Furthermore, taxonomic approaches are most frequently used, and few studies have compared the relative importance of local and regional control of trait versus the taxonomic composition in stream ecosystems., Using a spatially dense data set covering all stream sizes in a lowland European region of c. 42 000 km
2 and three organism groups (macrophytes, macroinvertebrates and fishes), we compared the relative importance of spatial and environmental determinants of species and trait composition in the study streams, classified into headwaters (stream order 1-2) and downstream sites (stream order >2)., We hypothesised that (i) there is a higher correspondence between environmental conditions and trait composition than with species composition, (ii) dispersal limitation (pure spatial structuring) is greater in headwaters than in downstream sites and (iii) dispersal limitation (pure spatial structuring) is weakest for macroinvertebrates, intermediate for macrophytes and strongest for fishes., The most consistent pattern across organisms and stream order groups was a higher correspondence between environmental variation and trait composition as well as a higher number of environmental variables significantly related to trait composition than with species composition (hypothesis 1). Spatial structuring peaked in headwater macrophyte communities and downstream fish communities (hypotheses 2 & 3) - a pattern that was amplified when separate analyses of traits describing species dispersal potential were undertaken., Our study highlights the potential of traits to capture multiple environmental changes in stream ecosystems and illustrates how organism-specific and highly context-dependent patterns in community organisation can emerge as a consequence of interactions between habitat connectivity (i.e. top versus lower parts of the stream network) and organism dispersal potential. [ABSTRACT FROM AUTHOR]- Published
- 2017
- Full Text
- View/download PDF
5. Pyrethroid effects on freshwater invertebrates: A meta-analysis of pulse exposures.
- Author
-
Rasmussen, Jes Jessen, Wiberg-Larsen, Peter, Kristensen, Esben Astrup, Cedergreen, Nina, and Friberg, Nikolai
- Subjects
PYRETHROIDS & the environment ,FRESHWATER invertebrates ,PESTICIDE content of water ,META-analysis ,DAPHNIA magna ,DOSE-response relationship in poisons ,ECOLOGICAL risk assessment - Abstract
Abstract: Pyrethroids are widely used insecticides that may seriously harm aquatic organisms. Being strongly hydrophobic, pyrethroids in solution occur only in short pulses but may be retained in sediments for longer periods. Consequently, most studies consider the chronic exposure of sediment dwelling organisms. We collected data from 16 studies to determine effect thresholds for stream macroinvertebrates exposed to short pyrethroid pulses evaluating lethal and sublethal ecologically relevant endpoints. Dose–response models showed EC50 for lethality, functional and behavioural endpoints down to 1/100, 1/100 and 1/1000 of the 48 h LC50 for Daphnia magna, respectively. The results indicate that the overall sensitivity of stream macroinvertebrates to pyrethroids may be higher than previously believed. This review shows the relevance of incorporating data on sublethal endpoints and appropriate post-exposure observation periods in future studies. The current risk assessment procedures and the higher tier approach are discussed in the light of our results. [Copyright &y& Elsevier]
- Published
- 2013
- Full Text
- View/download PDF
6. Stream habitat structure influences macroinvertebrate response to pesticides.
- Author
-
Rasmussen, Jes Jessen, Wiberg-Larsen, Peter, Baattrup-Pedersen, Annette, Friberg, Nikolai, and Kronvang, Brian
- Subjects
EFFECT of water pollution on aquatic organisms ,PESTICIDE content of water ,TOXICOLOGY of water pollution ,AQUATIC invertebrate populations ,ECOLOGICAL risk assessment ,ECOSYSTEM health ,AQUATIC habitats - Abstract
Agricultural pesticides continue to impair surface water ecosystems, although there are few assessments of interactions with other modifications such as fine sediment and physical alteration for flood drainage. We, therefore, surveyed pesticide contamination and macroinvertebrates in 14 streams along a gradient of expected pesticide exposure using a paired-reach approach to differentiate effects between physically modified and less modified sites. Apparent pesticides effects on the relative abundance of SPEcies At Risk (SPEAR) were increased at sites with degraded habitats primarily due to the absence of species with specific preferences for hard substrates. Our findings highlight the importance of physical habitat degradation in the assessment and mitigation of pesticide risk in agricultural streams. [Copyright &y& Elsevier]
- Published
- 2012
- Full Text
- View/download PDF
7. Impacts of pesticides and natural stressors on leaf litter decomposition in agricultural streams
- Author
-
Rasmussen, Jes Jesssen, Wiberg-Larsen, Peter, Baattrup-Pedersen, Annette, Monberg, Rikke Juul, and Kronvang, Brian
- Subjects
- *
ENVIRONMENTAL impact analysis , *PESTICIDES , *AGRICULTURAL pests , *BIOTIC communities , *ENVIRONMENTAL engineering , *HABITATS , *PLANT litter decomposition , *EUTROPHICATION - Abstract
Abstract: Agricultural pesticides are known to significantly impact the composition of communities in stream ecosystems. Moreover, agricultural streams are often characterised by loss of physical habitat diversity which may impose additional stress resulting from suboptimal environmental conditions. We surveyed pesticide contamination and rates of leaf litter decomposition in 14 1st and 2nd order Danish streams using litter bags with coarse and fine mesh sizes. Two sites differing in physical habitat complexity were sampled in each stream, and we used this approach to differentiate the effects of pesticides between sites with uniform (silt and sand) and more heterogeneous physical properties. Microbial litter decomposition was reduced by a factor two to four in agricultural streams compared to forested streams, and we found that the rate of microbial litter decomposition responded most strongly to pesticide toxicity for microorganisms and not to eutrophication. Moreover, the rate of microbial litter decomposition was generally 50% lower at sites with uniform physical habitats dominated by soft substrate compared to the sites with more heterogeneous physical habitats. The rate of macroinvertebrate shredding activity was governed by the density of shredders, and the density of shredders was not correlated to pesticide contamination mainly due to high abundances of the amphipod Gammarus pulex at all sites. Our study provides the first field based results on the importance of multiple stressors and their potential to increase the effect of agricultural pesticides on important ecosystem processes. [Copyright &y& Elsevier]
- Published
- 2012
- Full Text
- View/download PDF
8. Repeated insecticide pulses increase harmful effects on stream macroinvertebrate biodiversity and function.
- Author
-
Wiberg-Larsen, Peter, Nørum, Ulrik, and Rasmussen, Jes Jessen
- Subjects
INSECTICIDES ,RIVER channels ,BIOTIC communities ,FOREST litter ,GAMMARUS pulex ,RIVERS - Abstract
We exposed twelve mesocosm stream channels and four instream channels to one, two, and four pulses of the insecticide lambda-cyhalothrin (0.1 μg L
−1 ) applied at two day intervals, each pulse lasting 90 min. Unexposed controls were included. We monitored macroinvertebrate taxonomic composition in the channels and in deployed leaf packs one day before and 29 days after the first exposure. Further, we measured drift in and out of the channels and leaf litter decomposition. Lambda-cyhalothrin exposures induced significantly increased drift in both experiments especially for Gammarus pulex , Amphinemura standfussi , and Leuctra spp. Macroinvertebrate taxonomic composition increasingly changed with increasing number of lambda-cyhalothrin exposures being most pronounced in the mesocosm channels. Further, leaf decomposition significantly decreased with increasing number of exposures in the mesocosm channels. Our study showed that species with predicted highest sensitivity to lambda-cyhalothrin were primary drivers of significant changes in taxonomic composition lasting for at least one month despite continuous recolonization of exposed channels from upstream parts of the natural stream and from the water inlet in the mesocosm channels. The overall results highlight the importance of sequential exposures to insecticides for understanding the full impact of insecticides on macroinvertebrates at the community level in streams. Image 1 • Sequential exposures increased changes in macroinvertebrate community structure. • Sequential exposures decreased leaf litter decomposition. • Species with predicted high pyrethroid sensitivity governed community changes. Increasing number of sequential exposures with lambda-cyhalothrin increased changes in macroinvertebrate community structure and decreased their ecological function. [ABSTRACT FROM AUTHOR]- Published
- 2021
- Full Text
- View/download PDF
9. Macroinvertebrate communities along the main stem and tributaries of a pre-Alpine river: composition responds to altitude, richness does not.
- Author
-
Jacobsen, Dean, Wiberg-Larsen, Peter, Brodersen, Klaus P., Hansen, Søren Birkholm, Lindegaard, Claus, Friberg, Nikolai, Dall, Peter C., Kirkegaard, Jørn, Skriver, Jens, and Toman, Mihael
- Subjects
ALTITUDES ,COMMUNITIES ,RIVERS ,RIVER channels ,ENVIRONMENTAL sampling - Abstract
We collected quantitative macroinvertebrate samples and measured environmental and geographical parameters at 13 sites: six along the main stem and seven in tributaries close to the main channel over a 700 m gradient in altitude and 22 km longitudinal distance along the River Kokra in the Slovenian Alps. Our objectives were 1) to compare longitudinal patterns in richness and community composition between main stem and tributary sites, and 2) to determine the relative importance of the replacement and richness difference component for overall beta diversity and of environmental versus spatial distance on beta diversity among main stem and tributary sites. In total 138 taxa were identified. There were no differences between main stem and tributary sites in mean abundance or taxon richness (67 and 58, respectively). A nMDS and ANOSIM based on Bray-Curtis similarities found no separation of main stem and tributary sites, but that upper (≥880 m a.s.l) and lower sites (≤680 m a.s.l.) formed two different groups. In both main stem and tributaries taxon richness increased only slightly going downstream while the community composition (DCA1) was much better explained by altitude and distance from source. Overall, beta diversity (Sørensen and Bray-Curtis dissimilarity) was similar for the two groups, and total Sørensen dissimilarity was driven mainly by replacement in main stem (78 %) and tributary sites (77 %). Mantel tests showed that main stem dissimilarities were significantly correlated to environmental PCA distance, watercourse distance, overland distance and altitudinal differences. Tributary dissimilarities were not correlated to any of these four factors. GLMs showed that dissimilarity among main stem sites was explained only by altitude difference, while no factors were significant among tributary sites, even though nearly so for environmental PCA distance. The study illustrates the importance of measuring beta diversity along ecological gradients, such as river continua and/or altitudinal gradients, where alpha diversity may fail to detect relatively minor changes in assemblage composition. Such changes are likely to occur due to present and future climate warming. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
10. Pesticide impacts on predator–prey interactions across two levels of organisation.
- Author
-
Rasmussen, Jes Jessen, Nørum, Ulrik, Jerris, Morten Rygaard, Wiberg-Larsen, Peter, Kristensen, Esben Astrup, and Friberg, Nikolai
- Subjects
- *
PESTICIDES , *PREDATION , *CYHALOTHRIN , *GAMMARUS pulex , *AMPHIPODA , *BEHAVIOR - Abstract
Highlights: [•] Lambda-cyhalothrin overrules anti-predator behaviour of Gammarus pulex during exposure. [•] Lambda-cyhalothrin overrules predator behaviour of G. pulex during exposure. [•] Sublethal lambda-cyhalothrin concentrations may have cascading effects. [Copyright &y& Elsevier]
- Published
- 2013
- Full Text
- View/download PDF
11. Effects of a triazole fungicide and a pyrethroid insecticide on the decomposition of leaves in the presence or absence of macroinvertebrate shredders
- Author
-
Rasmussen, Jes Jessen, Monberg, Rikke Juul, Baattrup-Pedersen, Annette, Cedergreen, Nina, Wiberg-Larsen, Peter, Strobel, Bjarne, and Kronvang, Brian
- Subjects
- *
TRIAZOLES , *FUNGICIDES , *PYRETHROIDS , *FOLIAR diagnosis , *DAPHNIA magna , *EUROPEAN beech , *PROPICONAZOLE , *INVERTEBRATES - Abstract
Abstract: Previously, laboratory experiments have revealed that freely diluted azole fungicides potentiate the direct toxic effect of pyrethroid insecticides on Daphnia magna. More ecologically relevant exposure scenarios where pesticides are adsorbed have not been addressed. In this study we exposed beech leaves (Fagus sylvatica) to the azole fungicide propiconazole (50 or 500μgL−1), the pyrethroid insecticide alpha-cypermethrin (0.1 or 1μgL−1) or any combination of the two for 3h. Exposed leaves were transferred to aquaria with or without an assemblage of macroinvertebrate shredders, and we studied treatment effects on rates of microbial leaf decomposition, microbial biomass (using C:N ratio as a surrogate measure) and macroinvertebrate shredding activity during 26 days post-exposure. Microbial leaf decomposition rates were significantly reduced in the propiconazole treatments, and the reduction in microbial activity was significantly correlated with loss of microbial biomass (increased C:N ratio). Macroinvertebrate shredding activity was significantly reduced in the alpha-cypermethrin treatments. In addition, the macroinvertebrate assemblage responded to the propiconazole treatments by increasing their consumption of leaf litter with lower microbial biomass, probably to compensate for the reduced nutritional quality of this leaf litter. We found no interaction between the two pesticides on macroinvertebrate shredding activity, using Independent Action as a reference model. In terms of microbial leaf decomposition rates, however, alpha-cypermethrin acted as an antagonist on propiconazole. Based on these results we emphasise the importance of considering indirect effects of pesticides in the risk assessment of surface water ecosystems. [Copyright &y& Elsevier]
- Published
- 2012
- Full Text
- View/download PDF
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.