| 1. |
- Hladyz, Sally, et al.
(författare)
-
Stream ecosystem functioning in an agricultural landscape : the importance of terrestrial-aquatic linkages
- 2011
-
Ingår i: Ecosystems in a human-modified landscape. - San Diego : Academic Press. - 9780123747945 ; 44, s. 211-276
-
Bokkapitel (refereegranskat)abstract
- The loss of native riparian vegetation and its replacement with non-native species or grazing land for agriculture is a worldwide phenomenon, but one that is prevalent in Europe, reflecting the heavily-modified nature of the continent's landscape. The consequences of these riparian alterations for freshwater ecosystems remain largely unknown, largely because bioassessment has traditionally focused on the impacts of organic pollution on community structure. We addressed the need for a broader perspective, which encompasses changes at the catchment scale, by comparing ecosystem processes in woodland reference sites with those with altered riparian zones. We assessed a range of riparian modifications, including clearance for pasture and replacement of woodland with a range of low diversity plantations, in 100 streams to obtain a continental-scale perspective of the major types of alterations across Europe. Subsequently, we focused on pasture streams, as an especially prevalent widespread riparian alteration, by characterising their structural (e.g. invertebrate and fish communities) and functional (e.g. litter decomposition, algal production, herbivory) attributes in a country (Ireland) dominated by this type of landscape modification, via field and laboratory experiments. We found that microbes became increasingly important as agents of decomposition relative to macrofauna (invertebrates) in impacted sites in general and in pasture streams in particular. Resource quality of grass litter (e.g., carbon : nutrient ratios, lignin and cellulose content) was a key driver of decomposition rates in pasture streams. These systems also relied more heavily on autochthonous algal production than was the case in woodland streams, which were more detrital based. These findings suggest that these pasture streams might be fundamentally different from their native, ancestral woodland state, with a shift towards greater reliance on autochthonous-based processes. This could have a destabilizing effect on the dynamics of the food web relative to the slower, detrital-based pathways that dominate in woodland streams.
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| 2. |
- Chauvet, Eric, et al.
(författare)
-
Litter decomposition as an indicator of stream ecosystem functioning at local-to-continental scales : insights from the European RivFunction project
- 2016
-
Ingår i: Large-scale ecology. - London : Academic Press. - 9780081009352 ; 55, s. 99-182
-
Bokkapitel (refereegranskat)abstract
- RivFunction is a pan-European initiative that started in 2002 and was aimed at establishing a novel functional-based approach to assessing the ecological status of rivers. Litter decomposition was chosen as the focal process because it plays a central role in stream ecosystems and is easy to study in the field. Impacts of two stressors that occur across the continent, nutrient pollution and modified riparian vegetation, were examined at > 200 paired sites in nine European ecoregions. In response to the former, decomposition was dramatically slowed at both extremes of a 1000-fold nutrient gradient, indicating nutrient limitation in unpolluted sites, highly variable responses across Europe in moderately impacted streams, and inhibition via associated toxic and additional stressors in highly polluted streams. Riparian forest modification by clear cutting or replacement of natural vegetation by plantations (e.g. conifers, eucalyptus) or pasture produced similarly complex responses. Clear effects caused by specific riparian disturbances were observed in regionally focused studies, but general trends across different types of riparian modifications were not apparent, in part possibly because of important indirect effects. Complementary field and laboratory experiments were undertaken to tease apart the mechanistic drivers of the continental scale field bioassays by addressing the influence of litter, fungal and detritivore diversity. These revealed generally weak and context-dependent effects on decomposition, suggesting high levels of redundancy (and hence potential insurance mechanisms that can mitigate a degree of species loss) within the food web. Reduced species richness consistently increased decomposition variability, if not the absolute rate. Further field studies were aimed at identifying important sources of this variability (e.g. litter quality, temporal variability) to help constrain ranges of predicted decomposition rates in different field situations. Thus, although many details still need to be resolved, litter decomposition holds considerable potential in some circumstances to capture impairment of stream ecosystem functioning. For instance, species traits associated with the body size and metabolic capacity of the consumers were often the main driver at local scales, and these were often translated into important determinants of otherwise apparently contingent effects at larger scales. Key insights gained from conducting continental scale studies included resolving the apparent paradox of inconsistent relationships between nutrients and decomposition rates, as the full complex multidimensional picture emerged from the large-scale dataset, of which only seemingly contradictory fragments had been seen previously.
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| 3. |
- Chauvet, Eric, et al.
(författare)
-
Litter decomposition as an indicator of stream ecosystem functioning at local-to-continental scales : insights from the European RivFunction project
- 2016
-
Ingår i: Large-scale ecology. - London : Academic Press. ; 55, s. 99-182
-
Bokkapitel (populärvet., debatt m.m.)abstract
- RivFunction is a pan-European initiative that started in 2002 and was aimed at establishing a novel functional-based approach to assessing the ecological status of rivers. Litter decomposition was chosen as the focal process because it plays a central role in stream ecosystems and is easy to study in the field. Impacts of two stressors that occur across the continent, nutrient pollution and modified riparian vegetation, were examined at > 200 paired sites in nine European ecoregions. In response to the former, decomposition was dramatically slowed at both extremes of a 1000-fold nutrient gradient, indicating nutrient limitation in unpolluted sites, highly variable responses across Europe in moderately impacted streams, and inhibition via associated toxic and additional stressors in highly polluted streams. Riparian forest modification by clear cutting or replacement of natural vegetation by plantations (e.g. conifers, eucalyptus) or pasture produced similarly complex responses. Clear effects caused by specific riparian disturbances were observed in regionally focused studies, but general trends across different types of riparian modifications were not apparent, in part possibly because of important indirect effects. Complementary field and laboratory experiments were undertaken to tease apart the mechanistic drivers of the continental scale field bioassays by addressing the influence of litter, fungal and detritivore diversity. These revealed generally weak and context-dependent effects on decomposition, suggesting high levels of redundancy (and hence potential insurance mechanisms that can mitigate a degree of species loss) within the food web. Reduced species richness consistently increased decomposition variability, if not the absolute rate. Further field studies were aimed at identifying important sources of this variability (e.g. litter quality, temporal variability) to help constrain ranges of predicted decomposition rates in different field situations. Thus, although many details still need to be resolved, litter decomposition holds considerable potential in some circumstances to capture impairment of stream ecosystem functioning. For instance, species traits associated with the body size and metabolic capacity of the consumers were often the main driver at local scales, and these were often translated into important determinants of otherwise apparently contingent effects at larger scales. Key insights gained from conducting continental scale studies included resolving the apparent paradox of inconsistent relationships between nutrients and decomposition rates, as the full complex multidimensional picture emerged from the large-scale dataset, of which only seemingly contradictory fragments had been seen previously.
|
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| 4. |
- Hladyz, Sally, et al.
(författare)
-
Stream ecosystem functioning in an agricultural landscape : the importance of terrestrial-aquatic linkages
- 2011
-
Ingår i: Ecosystems in a human-modified landscape. - San Diego : Academic Press. - 9780123747945 ; 44, s. 211-276
-
Bokkapitel (populärvet., debatt m.m.)abstract
- The loss of native riparian vegetation and its replacement with non-native species or grazing land for agriculture is a worldwide phenomenon, but one that is prevalent in Europe, reflecting the heavily-modified nature of the continent's landscape. The consequences of these riparian alterations for freshwater ecosystems remain largely unknown, largely because bioassessment has traditionally focused on the impacts of organic pollution on community structure. We addressed the need for a broader perspective, which encompasses changes at the catchment scale, by comparing ecosystem processes in woodland reference sites with those with altered riparian zones. We assessed a range of riparian modifications, including clearance for pasture and replacement of woodland with a range of low diversity plantations, in 100 streams to obtain a continental-scale perspective of the major types of alterations across Europe. Subsequently, we focused on pasture streams, as an especially prevalent widespread riparian alteration, by characterising their structural (e.g. invertebrate and fish communities) and functional (e.g. litter decomposition, algal production, herbivory) attributes in a country (Ireland) dominated by this type of landscape modification, via field and laboratory experiments. We found that microbes became increasingly important as agents of decomposition relative to macrofauna (invertebrates) in impacted sites in general and in pasture streams in particular. Resource quality of grass litter (e.g., carbon : nutrient ratios, lignin and cellulose content) was a key driver of decomposition rates in pasture streams. These systems also relied more heavily on autochthonous algal production than was the case in woodland streams, which were more detrital based. These findings suggest that these pasture streams might be fundamentally different from their native, ancestral woodland state, with a shift towards greater reliance on autochthonous-based processes. This could have a destabilizing effect on the dynamics of the food web relative to the slower, detrital-based pathways that dominate in woodland streams.
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| 5. |
- Mark, O., et al.
(författare)
-
Application of hydroinformatics tools for water quality modeling and management : case study of Vientiane, Lao PDR
- 2010
-
Ingår i: Journal of Hydroinformatics. - 1464-7141 .- 1465-1734. ; 12:2, s. 161-171
-
Tidskriftsartikel (refereegranskat)abstract
- The application of hydroinformatics tools is restricted in developing countries due to the non-availability of the required data and information under local conditions. This paper presents the state of water quality of the city of Vientiane (capital of Lao PDR) before the extensive rectification of its drainage network and describes an approach and methodology for water quality modeling. This is done with respect to the application of a combined hydrodynamic/water quality model based on minimal input data and observations for model verification. It further evaluates options to improve the deteriorating water quality observed in the rectified channels associated with the absence of suitable wastewater treatment. Two pollutants associated with the enrichment of receiving water bodies by wastewaters, total-P and NH4-N, are modeled. The modelling study is carried out in three steps: dry weather flow simulation, wet weather flow simulation and nutrient modeling using MOUSE. The dry weather flow simulations are carried out to calibrate the model for hydraulic roughness coefficient, dispersion coefficient and travel time. The wet weather flow simulations analyze the effect on flooding of two channel states, namely unvegetated and vegetated conditions. Nutrient modeling therefore evaluates removal efficiency by the vegetation. Model results are compared with the observed data and recommendations are made with respect to the predicted effects of the water quality improvement schemes studied. In conclusion, the modeling approach herein presented can be applied for performance analyses of urban channels in the developing part of the world, where data are often limited.
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| 6. |
- Mark, O., et al.
(författare)
-
Application of hydroinformatics tools for water quality modeling and management : case study of Vientiane, Lao PDR
- 2010
-
Ingår i: Journal of Hydroinformatics. - : IWA Publishing. - 1464-7141 .- 1465-1734. ; 12:2, s. 161-171
-
Tidskriftsartikel (refereegranskat)abstract
- The application of hydroinformatics tools is restricted in developing countries due to the non-availability of the required data and information under local conditions. This paper presents the state of water quality of the city of Vientiane (capital of Lao PDR) before the extensive rectification of its drainage network and describes an approach and methodology for water quality modeling. This is done with respect to the application of a combined hydrodynamic/water quality model based on minimal input data and observations for model verification. It further evaluates options to improve the deteriorating water quality observed in the rectified channels associated with the absence of suitable wastewater treatment. Two pollutants associated with the enrichment of receiving water bodies by wastewaters, total-P and NH4-N, are modeled. The modelling study is carried out in three steps: dry weather flow simulation, wet weather flow simulation and nutrient modeling using MOUSE. The dry weather flow simulations are carried out to calibrate the model for hydraulic roughness coefficient, dispersion coefficient and travel time. The wet weather flow simulations analyze the effect on flooding of two channel states, namely unvegetated and vegetated conditions. Nutrient modeling therefore evaluates removal efficiency by the vegetation. Model results are compared with the observed data and recommendations are made with respect to the predicted effects of the water quality improvement schemes studied. In conclusion, the modeling approach herein presented can be applied for performance analyses of urban channels in the developing part of the world, where data are often limited.
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| 7. |
- Woodward, Guy, et al.
(författare)
-
Continental-scale effects of nutrient pollution on stream ecosystem functioning
- 2012
-
Ingår i: Science. - : American Association for the Advancement of Science. - 0036-8075 .- 1095-9203. ; 336:6087, s. 1438-1440
-
Tidskriftsartikel (refereegranskat)abstract
- Excessive nutrient loading is a major threat to aquatic ecosystems worldwide that leads to profound changes in aquatic biodiversity and biogeochemical processes. Systematic quantitative assessment of functional ecosystem measures for river networks is, however, lacking, especially at continental scales. Here, we narrow this gap by means of a pan-European field experiment on a fundamental ecosystem process—leaf-litter breakdown—in 100 streams across a greater than 1000-fold nutrient gradient. Dramatically slowed breakdown at both extremes of the gradient indicated strong nutrient limitation in unaffected systems, potential for strong stimulation in moderately altered systems, and inhibition in highly polluted streams. This large-scale response pattern emphasizes the need to complement established structural approaches (such as water chemistry, hydrogeomorphology, and biological diversity metrics) with functional measures (such as litter-breakdown rate, whole-system metabolism, and nutrient spiraling) for assessing ecosystem health.
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| 8. |
- Back, C, et al.
(författare)
-
High-dosage treatment of a Quebec stream with Bacillus thuringiensis serovar. israelensis : efficacy against black fly larvae (Diptera, Simuliidae) and impact on nontarget insects
- 1985
-
Ingår i: Canadian Entomologist. - 0008-347X .- 1918-3240. ; 117:12, s. 1523-1534
-
Tidskriftsartikel (refereegranskat)abstract
- A typical lake outlet of the Canadian Shield was treated for 15 min with a high dose (5.28 g/L s−1 of discharge) of Teknar®, a commercial formulation of Bacillus thuringiensis serovar. israelensis. Efficacy on Simuliidae larvae and impact on non-target aquatic insects of this stream were monitored using drift nets, counting plates, and artificial turf substrates along a 1000-m section downstream of the site of application. Compared with a 4-day pre-treatment average for 12-h sampling periods, drift of Simuliidae increased from 64 to 92 ×, with shorter peaks of 133–184 ×, 2–6 h after treatment. There was no evident drift increase in larvae of Ephemeroptera, Plecoptera, Trichoptera, Chironomidae, or dipterous pupae, but larvae of Blephariceridae (Diptera) were severely affected as their drift was increased by up to 50 × and remained high for 3 days. After 30 h the mortality of Simuliidae on counting plates ranged from 95 to 82% in the first 300 m, with detachment rates of 78.5–46.5%. Densities of non-target insect larvae were not reduced on the artificial substrates, except for 2 genera of Chironomidae (Eukiefferella and Polypedilum) which were reduced 26 to 39% of their original density. Drifting larvae of 1 chironomid genus (Phaenopsectra) also showed symptoms of toxemia by B.t.i. The main impact of the treatment was thus seen in 2 Nematocera families (Chironomidae and Blephariceridae) which were mainly exposed to B.t.i. sedimented on the bottom of the stream or attached to periphyton growing on rocks.
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| 9. |
- Back, C, et al.
(författare)
-
High-dosage treatment of a Quebec stream with Bacillus thuringiensis serovar. israelensis : efficacy against black fly larvae (Diptera, Simuliidae) and impact on nontarget insects
- 1985
-
Ingår i: Canadian Entomologist. - : Cambridge University Press. - 0008-347X .- 1918-3240. ; 117:12, s. 1523-1534
-
Tidskriftsartikel (refereegranskat)abstract
- A typical lake outlet of the Canadian Shield was treated for 15 min with a high dose (5.28 g/L s−1 of discharge) of Teknar®, a commercial formulation of Bacillus thuringiensis serovar. israelensis. Efficacy on Simuliidae larvae and impact on non-target aquatic insects of this stream were monitored using drift nets, counting plates, and artificial turf substrates along a 1000-m section downstream of the site of application. Compared with a 4-day pre-treatment average for 12-h sampling periods, drift of Simuliidae increased from 64 to 92 ×, with shorter peaks of 133–184 ×, 2–6 h after treatment. There was no evident drift increase in larvae of Ephemeroptera, Plecoptera, Trichoptera, Chironomidae, or dipterous pupae, but larvae of Blephariceridae (Diptera) were severely affected as their drift was increased by up to 50 × and remained high for 3 days. After 30 h the mortality of Simuliidae on counting plates ranged from 95 to 82% in the first 300 m, with detachment rates of 78.5–46.5%. Densities of non-target insect larvae were not reduced on the artificial substrates, except for 2 genera of Chironomidae (Eukiefferella and Polypedilum) which were reduced 26 to 39% of their original density. Drifting larvae of 1 chironomid genus (Phaenopsectra) also showed symptoms of toxemia by B.t.i. The main impact of the treatment was thus seen in 2 Nematocera families (Chironomidae and Blephariceridae) which were mainly exposed to B.t.i. sedimented on the bottom of the stream or attached to periphyton growing on rocks.
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| 10. |
- Djerf, Henric, et al.
(författare)
-
Can wetlands reduce humic substances in forested streams : combining two approaches to characterize efficiency
- 2018
-
Ingår i: Book of abstracts. - 9789188898289
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Establishing statistical significance in assessing wetland performance can be quite challenging when reduction in the monitored substance is very small and temporarily variable. Assessing colour changes associated with humic substances is such a situation. One of the most important parameters of any evaluation of wetland treatment performances is the retention time of the water before it exit the wetland. This can be theoretically estimated, but even better measured directly with the help of a tracing agent. In this research, the approach is based on the simultaneously assessment of hydraulic retention time using conservative tracing (Rhodamine WT) and a mass balance based removal efficiency assessment (regression slope of the summation mass-in vs. summation mass-out).
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