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Eva Bergman - One of the best experts on this subject based on the ideXlab platform.
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Effects of woody debris and the supply of Terrestrial Invertebrates on the diet and growth of brown trout (Salmo trutta) in a boreal stream
Freshwater Biology, 2014Co-Authors: Pär Gustafsson, Larry Greenberg, Eva BergmanAbstract:SUMMARY 1. Changes to the riparian vegetation of forest streams during timber harvesting may have considerable impacts on stream biota, but few studies have attempted to separate the effects of individual factors that are altered during clear-felling operations. 2. We studied the effects of large wood and Terrestrial Invertebrate supply, two factors affected by forest harvesting, on the growth and diet of two size classes of brown trout (Salmo trutta) during a two-month (June–August) field enclosure experiment. Twelve 20-m-long enclosed stream reaches were used in a 2 9 2 factorial design, with large wood either absent or added to mimic pre-modern forestry conditions, and Terrestrial Invertebrate inputs either reduced or maintained at ambient levels. 3. The addition of large wood had a positive effect on the growth of large trout but no effect on small trout, whereas Terrestrial Invertebrate input had no effect on the growth of either size class. Growth rates were highest in the treatment with ambient Terrestrial Invertebrate inputs and added wood, were lowest in the treatment with reduced Terrestrial Invertebrate inputs and no added wood and were intermediate in the other two treatments. 4. Dietary analyses showed no difference in treatments with and without added wood, perhaps because instream wood influences growth by producing profitable stream positions for trout, rather than by acting as a source of prey. Terrestrial Invertebrate inputs affected the diet, as trout in enclosures with reduced inputs had a lower proportion of Terrestrial Invertebrate biomass in the diet than trout in enclosures with ambient Terrestrial inputs. 5. Our results suggest that leaving woody debris in streams when harvesting forests may enhance trout growth and that this is probably due to the physical changes in depth and current velocity caused by the wood rather than to changes in dietary prey composition.
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Woody debris and Terrestrial Invertebrates – effects on prey resources for brown trout (Salmo trutta) in a boreal stream
Environmental Biology of Fishes, 2014Co-Authors: Pär Gustafsson, Larry Greenberg, Eva BergmanAbstract:Intensive forestry and other activities that alter riparian vegetation may disrupt the connectivity and the flux of energy between Terrestrial and aquatic habitats and have large effects on biota, especially in small streams. We manipulated the amount of in-stream wood and the flux of Terrestrial Invertebrate subsidies to determine how these factors affected potential food resources for drift-feeding brown trout (Salmo trutta ) in a boreal Swedish forest stream. Specifically, we followed the effects on the abundance of aquatic and Terrestrial Invertebrate fauna from June to August 2007. The treatments were 1) addition of wood, unmanipulated Terrestrial Invertebrate inputs, 2) reduction of Terrestrial Invertebrate inputs (using canopy covers), no addition of wood, 3) unmanipulated ambient conditions, 4) simultaneous addition of wood and reduction of Terrestrial Invertebrate inputs. Added wood resulted in greater biomass of aquatic Invertebrate biomass, and both input and drift of Terrestrial Invertebrates were reduced by canopy covers. In terms of total potential prey biomass, the addition of wood with ambient levels of Terrestrial Invertebrate inputs had the highest standing crop of benthic, wood-living and Terrestrial Invertebrates combined, whereas the treatment with reduced Terrestrial input and no wood added had the lowest standing crop. Our study indicates that forest practices that both reduce the recruitment of wood and the input of Terrestrial Invertebrates to small streams have negative effects on prey availability for drift-feeding brown trout. The positive effects of wood addition on biomass of aquatic macroInvertebrates may partly compensate for the negative effects of reduced Terrestrial Invertebrate subsidies.
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Forest-Stream Linkages: Effects of Terrestrial Invertebrate Input and Light on Diet and Growth of Brown Trout (Salmo trutta) in a Boreal Forest Stream
PloS one, 2012Co-Authors: Tibor Erős, Larry Greenberg, Pär Gustafsson, Eva BergmanAbstract:Subsidies of energy and material from the riparian zone have large impacts on recipient stream habitats. Human-induced changes, such as deforestation, may profoundly affect these pathways. However, the strength of individual factors on stream ecosystems is poorly understood since the factors involved often interact in complex ways. We isolated two of these factors, manipulating the flux of Terrestrial input and the intensity of light in a 2×2 factorial design, where we followed the growth and diet of two size-classes of brown trout (Salmo trutta) and the development of periphyton, grazer macroInvertebrates, Terrestrial Invertebrate inputs, and drift in twelve 20 m long enclosed stream reaches in a five-month-long experiment in a boreal coniferous forest stream. We found that light intensity, which was artificially increased 2.5 times above ambient levels, had an effect on grazer density, but no detectable effect on chlorophyll a biomass. We also found a seasonal effect on the amount of drift and that the reduction of Terrestrial prey input, accomplished by covering enclosures with transparent plastic, had a negative impact on the amount of Terrestrial Invertebrates in the drift. Further, trout growth was strongly seasonal and followed the same pattern as drift biomass, and the reduction of Terrestrial prey input had a negative effect on trout growth. Diet analysis was consistent with growth differences, showing that trout in open enclosures consumed relatively more Terrestrial prey in summer than trout living in covered enclosures. We also predicted ontogenetic differences in the diet and growth of old and young trout, where we expected old fish to be more affected by the Terrestrial prey reduction, but we found little evidence of ontogenetic differences. Overall, our results showed that reduced Terrestrial prey inputs, as would be expected from forest harvesting, shaped differences in the growth and diet of the top predator, brown trout.
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Forest-stream linkages: the response of brown trout to woody and Terrestrial Invertebrate inputs
2011Co-Authors: Larry Greenberg, Eva Bergman, Pär GustafssonAbstract:Forest-stream linkages: the response of brown trout to woody and Terrestrial Invertebrate inputs
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Aquatic-Terrestrial linkages : effects of Terrestrial Invertebrate input and light on a boreal stream community
2011Co-Authors: Tibor Erős, Larry Greenberg, Pär Gustafsson, Eva BergmanAbstract:Riparian vegetation along streams and rivers affects the aquatic community in numerous ways and often operates as a link for energy flux between forest and streams. The studies presented in this licentiate thesis focus on light and Terrestrial Invertebrates, two factors influenced by riparian zone structure, which potentially affect stream ecosystems and thus also brown trout (Salmo trutta). Paper I is a laboratory experiment where I study size dependent foraging behavior on surface-drifting Terrestrial Invertebrates and benthic Invertebrates by brown trout. The results show a size-dependent difference in foraging ability with large trout being better able to use Terrestrial surface prey than small trout. I argue that such ontogenetic foraging differences are due to both morphological constraints (eg. gape limitation) and size dependent behavioral differences related to predation risk. Paper II consists of a 5 month-long 2x2 factorial design field experiment where my objective was to examine the effects of Terrestrial Invertebrate input and solar radiation (PAR) on different trophic levels in a boreal headwater stream. More specifically, I followed the effects of increased light and decreased Terrestrial Invertebrate subsidies on periphyton, benthic macroInvertebrates and two size classes of the top fish predator, brown trout. The results showed that the reduction of Terrestrial Invertebrate input had size- and seasonal-dependent effects on trout, where large trout had lower growth rates than small trout, mainly in summer. Diet analyses of trout supported growth differences in that large trout in unmanipulated enclosures consumed relatively more Terrestrial prey than large trout living in enclosures with reduced Terrestrial inputs. A higher reliance on Terrestrial prey subsidies by large trout compared to small may be explained by ontogenetic differences in foraging and habitat choice. Despite a 2.5-fold increase in PAR, light did not have an effect on chlorophyll a biomass, nor was there an effect on the density or composition of benthic macroInvertebrates. The lack of effects on primary production may be explained by very low nutrient levels in the stream.
Pär Gustafsson - One of the best experts on this subject based on the ideXlab platform.
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Effects of woody debris and the supply of Terrestrial Invertebrates on the diet and growth of brown trout (Salmo trutta) in a boreal stream
Freshwater Biology, 2014Co-Authors: Pär Gustafsson, Larry Greenberg, Eva BergmanAbstract:SUMMARY 1. Changes to the riparian vegetation of forest streams during timber harvesting may have considerable impacts on stream biota, but few studies have attempted to separate the effects of individual factors that are altered during clear-felling operations. 2. We studied the effects of large wood and Terrestrial Invertebrate supply, two factors affected by forest harvesting, on the growth and diet of two size classes of brown trout (Salmo trutta) during a two-month (June–August) field enclosure experiment. Twelve 20-m-long enclosed stream reaches were used in a 2 9 2 factorial design, with large wood either absent or added to mimic pre-modern forestry conditions, and Terrestrial Invertebrate inputs either reduced or maintained at ambient levels. 3. The addition of large wood had a positive effect on the growth of large trout but no effect on small trout, whereas Terrestrial Invertebrate input had no effect on the growth of either size class. Growth rates were highest in the treatment with ambient Terrestrial Invertebrate inputs and added wood, were lowest in the treatment with reduced Terrestrial Invertebrate inputs and no added wood and were intermediate in the other two treatments. 4. Dietary analyses showed no difference in treatments with and without added wood, perhaps because instream wood influences growth by producing profitable stream positions for trout, rather than by acting as a source of prey. Terrestrial Invertebrate inputs affected the diet, as trout in enclosures with reduced inputs had a lower proportion of Terrestrial Invertebrate biomass in the diet than trout in enclosures with ambient Terrestrial inputs. 5. Our results suggest that leaving woody debris in streams when harvesting forests may enhance trout growth and that this is probably due to the physical changes in depth and current velocity caused by the wood rather than to changes in dietary prey composition.
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Woody debris and Terrestrial Invertebrates – effects on prey resources for brown trout (Salmo trutta) in a boreal stream
Environmental Biology of Fishes, 2014Co-Authors: Pär Gustafsson, Larry Greenberg, Eva BergmanAbstract:Intensive forestry and other activities that alter riparian vegetation may disrupt the connectivity and the flux of energy between Terrestrial and aquatic habitats and have large effects on biota, especially in small streams. We manipulated the amount of in-stream wood and the flux of Terrestrial Invertebrate subsidies to determine how these factors affected potential food resources for drift-feeding brown trout (Salmo trutta ) in a boreal Swedish forest stream. Specifically, we followed the effects on the abundance of aquatic and Terrestrial Invertebrate fauna from June to August 2007. The treatments were 1) addition of wood, unmanipulated Terrestrial Invertebrate inputs, 2) reduction of Terrestrial Invertebrate inputs (using canopy covers), no addition of wood, 3) unmanipulated ambient conditions, 4) simultaneous addition of wood and reduction of Terrestrial Invertebrate inputs. Added wood resulted in greater biomass of aquatic Invertebrate biomass, and both input and drift of Terrestrial Invertebrates were reduced by canopy covers. In terms of total potential prey biomass, the addition of wood with ambient levels of Terrestrial Invertebrate inputs had the highest standing crop of benthic, wood-living and Terrestrial Invertebrates combined, whereas the treatment with reduced Terrestrial input and no wood added had the lowest standing crop. Our study indicates that forest practices that both reduce the recruitment of wood and the input of Terrestrial Invertebrates to small streams have negative effects on prey availability for drift-feeding brown trout. The positive effects of wood addition on biomass of aquatic macroInvertebrates may partly compensate for the negative effects of reduced Terrestrial Invertebrate subsidies.
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Forest-Stream Linkages: Effects of Terrestrial Invertebrate Input and Light on Diet and Growth of Brown Trout (Salmo trutta) in a Boreal Forest Stream
PloS one, 2012Co-Authors: Tibor Erős, Larry Greenberg, Pär Gustafsson, Eva BergmanAbstract:Subsidies of energy and material from the riparian zone have large impacts on recipient stream habitats. Human-induced changes, such as deforestation, may profoundly affect these pathways. However, the strength of individual factors on stream ecosystems is poorly understood since the factors involved often interact in complex ways. We isolated two of these factors, manipulating the flux of Terrestrial input and the intensity of light in a 2×2 factorial design, where we followed the growth and diet of two size-classes of brown trout (Salmo trutta) and the development of periphyton, grazer macroInvertebrates, Terrestrial Invertebrate inputs, and drift in twelve 20 m long enclosed stream reaches in a five-month-long experiment in a boreal coniferous forest stream. We found that light intensity, which was artificially increased 2.5 times above ambient levels, had an effect on grazer density, but no detectable effect on chlorophyll a biomass. We also found a seasonal effect on the amount of drift and that the reduction of Terrestrial prey input, accomplished by covering enclosures with transparent plastic, had a negative impact on the amount of Terrestrial Invertebrates in the drift. Further, trout growth was strongly seasonal and followed the same pattern as drift biomass, and the reduction of Terrestrial prey input had a negative effect on trout growth. Diet analysis was consistent with growth differences, showing that trout in open enclosures consumed relatively more Terrestrial prey in summer than trout living in covered enclosures. We also predicted ontogenetic differences in the diet and growth of old and young trout, where we expected old fish to be more affected by the Terrestrial prey reduction, but we found little evidence of ontogenetic differences. Overall, our results showed that reduced Terrestrial prey inputs, as would be expected from forest harvesting, shaped differences in the growth and diet of the top predator, brown trout.
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Forest-stream linkages: the response of brown trout to woody and Terrestrial Invertebrate inputs
2011Co-Authors: Larry Greenberg, Eva Bergman, Pär GustafssonAbstract:Forest-stream linkages: the response of brown trout to woody and Terrestrial Invertebrate inputs
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Aquatic-Terrestrial linkages : effects of Terrestrial Invertebrate input and light on a boreal stream community
2011Co-Authors: Tibor Erős, Larry Greenberg, Pär Gustafsson, Eva BergmanAbstract:Riparian vegetation along streams and rivers affects the aquatic community in numerous ways and often operates as a link for energy flux between forest and streams. The studies presented in this licentiate thesis focus on light and Terrestrial Invertebrates, two factors influenced by riparian zone structure, which potentially affect stream ecosystems and thus also brown trout (Salmo trutta). Paper I is a laboratory experiment where I study size dependent foraging behavior on surface-drifting Terrestrial Invertebrates and benthic Invertebrates by brown trout. The results show a size-dependent difference in foraging ability with large trout being better able to use Terrestrial surface prey than small trout. I argue that such ontogenetic foraging differences are due to both morphological constraints (eg. gape limitation) and size dependent behavioral differences related to predation risk. Paper II consists of a 5 month-long 2x2 factorial design field experiment where my objective was to examine the effects of Terrestrial Invertebrate input and solar radiation (PAR) on different trophic levels in a boreal headwater stream. More specifically, I followed the effects of increased light and decreased Terrestrial Invertebrate subsidies on periphyton, benthic macroInvertebrates and two size classes of the top fish predator, brown trout. The results showed that the reduction of Terrestrial Invertebrate input had size- and seasonal-dependent effects on trout, where large trout had lower growth rates than small trout, mainly in summer. Diet analyses of trout supported growth differences in that large trout in unmanipulated enclosures consumed relatively more Terrestrial prey than large trout living in enclosures with reduced Terrestrial inputs. A higher reliance on Terrestrial prey subsidies by large trout compared to small may be explained by ontogenetic differences in foraging and habitat choice. Despite a 2.5-fold increase in PAR, light did not have an effect on chlorophyll a biomass, nor was there an effect on the density or composition of benthic macroInvertebrates. The lack of effects on primary production may be explained by very low nutrient levels in the stream.
Mar Cabeza - One of the best experts on this subject based on the ideXlab platform.
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global meta analysis of the impacts of Terrestrial Invertebrate invaders on species communities and ecosystems
Global Ecology and Biogeography, 2016Co-Authors: Erin K. Cameron, Montserrat Vilà, Mar CabezaAbstract:Aim Terrestrial Invertebrates comprise a large proportion of alien species world-wide, yet a quantitative global synthesis of their effects on native species and ecosystems has not been explored. We conducted a meta-analysis to examine the ecological impacts of Terrestrial Invertebrate invaders and to test how impacts are modulated by the invader's trophic position, habitat attributes (i.e. insularity and disturbance) and the study methodology (observational versus experimental). Location Global. Methods We investigated the effects of Terrestrial Invertebrate invaders on populations, communities and ecosystems by conducting a random effects meta-analysis using 112 articles reporting data from 710 field and laboratory studies. The analysis included 16 insect, 11 earthworm, 7 slug and 1 nematode invaders. Results On average, across invaders, the presence of invaders reduced plant fitness (52%), animal diversity (33%) and animal abundance (29%). Leaf litter decomposition was 41% higher in the presence of invaders, while other ecosystem-level variables such as nutrient cycling were not affected in a consistent direction. Invasive predators and detritivores decreased animal abundance, whereas herbivores and omnivores had limited impacts. Single invaders increased soil nitrogen pools while multiple species did not. Insularity and disturbance did not affect the magnitude of the impacts significantly, mainly because there was a large variation among studies. Main conclusions Overall, our study indicates that Terrestrial Invertebrate invaders have significant consistent effects on populations, communities and ecosystems, with islands and disturbed sites not being more prone to impacts. However, effects vary considerably depending on the type of impact being examined and the trophic position of the invader. There is no evidence that invaders cause larger impacts when multiple species of invaders, rather than single invaders, are involved.
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Global meta‐analysis of the impacts of Terrestrial Invertebrate invaders on species, communities and ecosystems
Global Ecology and Biogeography, 2016Co-Authors: Erin K. Cameron, Montserrat Vilà, Mar CabezaAbstract:Aim Terrestrial Invertebrates comprise a large proportion of alien species world-wide, yet a quantitative global synthesis of their effects on native species and ecosystems has not been explored. We conducted a meta-analysis to examine the ecological impacts of Terrestrial Invertebrate invaders and to test how impacts are modulated by the invader's trophic position, habitat attributes (i.e. insularity and disturbance) and the study methodology (observational versus experimental). Location Global. Methods We investigated the effects of Terrestrial Invertebrate invaders on populations, communities and ecosystems by conducting a random effects meta-analysis using 112 articles reporting data from 710 field and laboratory studies. The analysis included 16 insect, 11 earthworm, 7 slug and 1 nematode invaders. Results On average, across invaders, the presence of invaders reduced plant fitness (52%), animal diversity (33%) and animal abundance (29%). Leaf litter decomposition was 41% higher in the presence of invaders, while other ecosystem-level variables such as nutrient cycling were not affected in a consistent direction. Invasive predators and detritivores decreased animal abundance, whereas herbivores and omnivores had limited impacts. Single invaders increased soil nitrogen pools while multiple species did not. Insularity and disturbance did not affect the magnitude of the impacts significantly, mainly because there was a large variation among studies. Main conclusions Overall, our study indicates that Terrestrial Invertebrate invaders have significant consistent effects on populations, communities and ecosystems, with islands and disturbed sites not being more prone to impacts. However, effects vary considerably depending on the type of impact being examined and the trophic position of the invader. There is no evidence that invaders cause larger impacts when multiple species of invaders, rather than single invaders, are involved.
Larry Greenberg - One of the best experts on this subject based on the ideXlab platform.
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Effects of woody debris and the supply of Terrestrial Invertebrates on the diet and growth of brown trout (Salmo trutta) in a boreal stream
Freshwater Biology, 2014Co-Authors: Pär Gustafsson, Larry Greenberg, Eva BergmanAbstract:SUMMARY 1. Changes to the riparian vegetation of forest streams during timber harvesting may have considerable impacts on stream biota, but few studies have attempted to separate the effects of individual factors that are altered during clear-felling operations. 2. We studied the effects of large wood and Terrestrial Invertebrate supply, two factors affected by forest harvesting, on the growth and diet of two size classes of brown trout (Salmo trutta) during a two-month (June–August) field enclosure experiment. Twelve 20-m-long enclosed stream reaches were used in a 2 9 2 factorial design, with large wood either absent or added to mimic pre-modern forestry conditions, and Terrestrial Invertebrate inputs either reduced or maintained at ambient levels. 3. The addition of large wood had a positive effect on the growth of large trout but no effect on small trout, whereas Terrestrial Invertebrate input had no effect on the growth of either size class. Growth rates were highest in the treatment with ambient Terrestrial Invertebrate inputs and added wood, were lowest in the treatment with reduced Terrestrial Invertebrate inputs and no added wood and were intermediate in the other two treatments. 4. Dietary analyses showed no difference in treatments with and without added wood, perhaps because instream wood influences growth by producing profitable stream positions for trout, rather than by acting as a source of prey. Terrestrial Invertebrate inputs affected the diet, as trout in enclosures with reduced inputs had a lower proportion of Terrestrial Invertebrate biomass in the diet than trout in enclosures with ambient Terrestrial inputs. 5. Our results suggest that leaving woody debris in streams when harvesting forests may enhance trout growth and that this is probably due to the physical changes in depth and current velocity caused by the wood rather than to changes in dietary prey composition.
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Woody debris and Terrestrial Invertebrates – effects on prey resources for brown trout (Salmo trutta) in a boreal stream
Environmental Biology of Fishes, 2014Co-Authors: Pär Gustafsson, Larry Greenberg, Eva BergmanAbstract:Intensive forestry and other activities that alter riparian vegetation may disrupt the connectivity and the flux of energy between Terrestrial and aquatic habitats and have large effects on biota, especially in small streams. We manipulated the amount of in-stream wood and the flux of Terrestrial Invertebrate subsidies to determine how these factors affected potential food resources for drift-feeding brown trout (Salmo trutta ) in a boreal Swedish forest stream. Specifically, we followed the effects on the abundance of aquatic and Terrestrial Invertebrate fauna from June to August 2007. The treatments were 1) addition of wood, unmanipulated Terrestrial Invertebrate inputs, 2) reduction of Terrestrial Invertebrate inputs (using canopy covers), no addition of wood, 3) unmanipulated ambient conditions, 4) simultaneous addition of wood and reduction of Terrestrial Invertebrate inputs. Added wood resulted in greater biomass of aquatic Invertebrate biomass, and both input and drift of Terrestrial Invertebrates were reduced by canopy covers. In terms of total potential prey biomass, the addition of wood with ambient levels of Terrestrial Invertebrate inputs had the highest standing crop of benthic, wood-living and Terrestrial Invertebrates combined, whereas the treatment with reduced Terrestrial input and no wood added had the lowest standing crop. Our study indicates that forest practices that both reduce the recruitment of wood and the input of Terrestrial Invertebrates to small streams have negative effects on prey availability for drift-feeding brown trout. The positive effects of wood addition on biomass of aquatic macroInvertebrates may partly compensate for the negative effects of reduced Terrestrial Invertebrate subsidies.
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Forest-Stream Linkages: Effects of Terrestrial Invertebrate Input and Light on Diet and Growth of Brown Trout (Salmo trutta) in a Boreal Forest Stream
PloS one, 2012Co-Authors: Tibor Erős, Larry Greenberg, Pär Gustafsson, Eva BergmanAbstract:Subsidies of energy and material from the riparian zone have large impacts on recipient stream habitats. Human-induced changes, such as deforestation, may profoundly affect these pathways. However, the strength of individual factors on stream ecosystems is poorly understood since the factors involved often interact in complex ways. We isolated two of these factors, manipulating the flux of Terrestrial input and the intensity of light in a 2×2 factorial design, where we followed the growth and diet of two size-classes of brown trout (Salmo trutta) and the development of periphyton, grazer macroInvertebrates, Terrestrial Invertebrate inputs, and drift in twelve 20 m long enclosed stream reaches in a five-month-long experiment in a boreal coniferous forest stream. We found that light intensity, which was artificially increased 2.5 times above ambient levels, had an effect on grazer density, but no detectable effect on chlorophyll a biomass. We also found a seasonal effect on the amount of drift and that the reduction of Terrestrial prey input, accomplished by covering enclosures with transparent plastic, had a negative impact on the amount of Terrestrial Invertebrates in the drift. Further, trout growth was strongly seasonal and followed the same pattern as drift biomass, and the reduction of Terrestrial prey input had a negative effect on trout growth. Diet analysis was consistent with growth differences, showing that trout in open enclosures consumed relatively more Terrestrial prey in summer than trout living in covered enclosures. We also predicted ontogenetic differences in the diet and growth of old and young trout, where we expected old fish to be more affected by the Terrestrial prey reduction, but we found little evidence of ontogenetic differences. Overall, our results showed that reduced Terrestrial prey inputs, as would be expected from forest harvesting, shaped differences in the growth and diet of the top predator, brown trout.
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Forest-stream linkages: the response of brown trout to woody and Terrestrial Invertebrate inputs
2011Co-Authors: Larry Greenberg, Eva Bergman, Pär GustafssonAbstract:Forest-stream linkages: the response of brown trout to woody and Terrestrial Invertebrate inputs
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Aquatic-Terrestrial linkages : effects of Terrestrial Invertebrate input and light on a boreal stream community
2011Co-Authors: Tibor Erős, Larry Greenberg, Pär Gustafsson, Eva BergmanAbstract:Riparian vegetation along streams and rivers affects the aquatic community in numerous ways and often operates as a link for energy flux between forest and streams. The studies presented in this licentiate thesis focus on light and Terrestrial Invertebrates, two factors influenced by riparian zone structure, which potentially affect stream ecosystems and thus also brown trout (Salmo trutta). Paper I is a laboratory experiment where I study size dependent foraging behavior on surface-drifting Terrestrial Invertebrates and benthic Invertebrates by brown trout. The results show a size-dependent difference in foraging ability with large trout being better able to use Terrestrial surface prey than small trout. I argue that such ontogenetic foraging differences are due to both morphological constraints (eg. gape limitation) and size dependent behavioral differences related to predation risk. Paper II consists of a 5 month-long 2x2 factorial design field experiment where my objective was to examine the effects of Terrestrial Invertebrate input and solar radiation (PAR) on different trophic levels in a boreal headwater stream. More specifically, I followed the effects of increased light and decreased Terrestrial Invertebrate subsidies on periphyton, benthic macroInvertebrates and two size classes of the top fish predator, brown trout. The results showed that the reduction of Terrestrial Invertebrate input had size- and seasonal-dependent effects on trout, where large trout had lower growth rates than small trout, mainly in summer. Diet analyses of trout supported growth differences in that large trout in unmanipulated enclosures consumed relatively more Terrestrial prey than large trout living in enclosures with reduced Terrestrial inputs. A higher reliance on Terrestrial prey subsidies by large trout compared to small may be explained by ontogenetic differences in foraging and habitat choice. Despite a 2.5-fold increase in PAR, light did not have an effect on chlorophyll a biomass, nor was there an effect on the density or composition of benthic macroInvertebrates. The lack of effects on primary production may be explained by very low nutrient levels in the stream.
T. Datry - One of the best experts on this subject based on the ideXlab platform.
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Ecological effects of flow intermittence in gravel bed rivers
2017Co-Authors: T. DatryAbstract:Rivers with intermittent flow regimes, those that do not flow permanently, are more abundant and widespread than previously thought, and may even make up more than half the global river network. Due to the nature of their streambed and the intensive hyporheic exchanges they experience, gravel-bed rivers (GBRs) are often temporally or spatially intermittent. Yet, this aspect of their flow regimes has been relatively overlooked. In this chapter I will use the recent developments of intermittent river ecology, a maturing and expanding discipline, to review various aspects of flow intermittence in GBRs. When possible, the specificities of GBRs and how these can make them different from other intermit- tent rivers will be highlighted. A first section will focus on defining terms and examine the quantitative importance and the distribution of these rivers. In a second section, I will use an eco-hydrological perspective at different spatial scales to illustrate the ecological implications of flow intermittence in GBRs. In a third section, I will expand on two aspects which, in my opinion, are really exciting and promising to explore in intermittent GBRs: the concept of disturbance ecology and the interaction between aquatic and Terrestrial components in these systems. I will finish this review by identifying some of the current research needs and perspectives. Two important points deserve to be mentioned here. First, because I have been working in various gravel-bed rivers that are flowing intermittently, many examples and results shown in this review are from my past and current research, whether it has been published or not. Obviously, these are examples among various others, since this research field is really blooming. Second, due to my expertise, many examples will concern aquatic and Terrestrial Invertebrate and fish communities, but clearly, other groups of organisms (e.g., plant, microbial communities) have been studied, as well as the effects of flow intermittence on ecosystem processes, which I will only briefly mention here.
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Temporal variations in dry riverbed Terrestrial Invertebrate: effects of dry duration
2012Co-Authors: R. Corti, T. DatryAbstract:When temporary rivers run dry, riverbeds shift from aquatic to Terrestrial conditions and are colonized by Terrestrial Invertebrates. However, this component of riverine biodiversity has been totally neglected by scientists and water managers. Particularly, nothing is known about temporal variations in Invertebrate assemblages during dry periods. In this study, we examined the structure and the composition of Terrestrial Invertebrate assemblages from dry riverbeds and adjacent riverbanks during a four-month dry period in two French temporary rivers. Invertebrates were collected using 140 pitfall traps positioned along 17 transects perpendicular to flow within 9 sites.We predicted i. river bank Invertebrates to be the primary source of riverbed Invertebrates ii. riverbed Invertebrate abundance and taxonomic richness to increase with the duration of dry periods and iii. composition of assemblages to shift with the duration of dry periods from hygrophilous to xerophilous and eurytopic dominated taxa. Invertebrate were being identified at the time of abstract submission and conclusions were unknown. However, this study will report for the very first time temporal variations in Terrestrial Invertebrates that could have implications in terms of dry riverbed management.
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Invertebrates and sestonic matter in an advancing wetted front travelling down a dry river bed (Albarine, France)
Freshwater Science, 2012Co-Authors: R. Corti, T. DatryAbstract:Temporary rivers are shifting mosaics of aquatic and Terrestrial habitat driven by hydrologic variability. Advancing wetted fronts (AWFs) that rewet dry river beds are unpredictable events, and knowledge about their composition and role in habitat mosaics is scarce. We collected dead and living Terrestrial Invertebrates, aquatic Invertebrates, and sestonic matter (i.e., suspended sediments and organic matter) entrained by flow in an AWF travelling downstream over a 7-km-long dry reach. We collected samples at 12 sites along the rewetting reach and at 3 sites in the upstream perennial reach of the Albarine River, France. Invertebrates in the AWF were mainly of Terrestrial origin and organic matter was essentially coarse (>5 mm). Terrestrial Invertebrate density and taxonomic richness and sestonic matter concentration were several orders of magnitude higher in the AWF than in the perennial reach. However, only Terrestrial Invertebrate taxonomic richness increased longitudinally. At least ⅓ of Terrestrial taxa could have survived submersion, and the density and taxonomic richness of these taxa decreased downstream. These results indicate that Terrestrially derived material is stored downstream during rewetting where it could greatly stimulate in-stream aquatic productivity and succession in Terrestrial Invertebrates along the riparian zone. In contrast, entrained aquatic taxa represented 15% of the benthic taxa collected 1 mo after rewetting, indicating a low contribution of AWFs to benthic Invertebrate succession. In the context of global change and increasing appropriation of water resources by humans, our results suggest that conceptual models of Invertebrate dynamic and organic matter processing in rivers should account for dry phases and transitional periods from dry to wet conditions.
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Surfing the wave: Invertebrate fluxes in the advancing wetted front of a temporary river following a 6 month dry period
2011Co-Authors: R. Corti, S. Charansol, T. DatryAbstract:Temporary rivers are alternating aquatic and Terrestrial ecosystems that are functionally linked. When rewetting of previously dry reaches occurs, shifts from Terrestrial to aquatic conditions can be brutal: Terrestrial Invertebrates colonizing dry riverbed may be flushed downstream, while aquatic Invertebrates from upstream perennial reaches may drift and colonize newly rewetted sediments. However, very little is known about the effects of advancing wetted fronts on aquatic and Terrestrial Invertebrates in temporary rivers. In this study, we examined advancing wetted front Invertebrate composition and fluxes at sites previously dried during 2 to 6 months. An important rainfall event triggered the rewetting of a 14-km long reach in the Albarine River (France), generating an advancing wetted front moving downstream at a rate of ~ 10m.min-1. We determined Invertebrate assemblage and fluxes in the advancing wetted front at 12 previously dry sites and 2 upstream perennial sites using drift nets and flow velocity recorders. Total Invertebrate fluxes at previously dry sites were 150-fold higher compared to perennial sites. Aquatic Invertebrates represented 40% of total drift fluxes at perennial sites, and only 10 % at previously dry sites. However, most of the Terrestrial Invertebrates in the advancing wetted front (i.e., > 95%) were dead. Furthermore, we found no longitudinal changes in aquatic and Terrestrial Invertebrate density and richness. These results suggest that rewetting is a catastrophic event for Terrestrial Invertebrates colonizing dry riverbeds rather than a possible mechanism for dispersion.