Abstract The invasive clam Corbicula fluminea has become a widespread benthic invertebrate in many freshwater ecosystems throughout Europe and North and South America. Invasive bivalves can dramatically alter the structure of native benthic communities, so understanding the factors responsible for successful invasion is important. We investigated C. fluminea nutritional requirements for essential lipids in a standardized growth experiment. Juvenile clams were fed different cyanobacteria (Aphanizomenon flos-aquae, Anabaena variabilis, Synechococcus elongatus) or eukaryotic algae (Scenedesmus obliquus, Cryptomonas sp.). Somatic growth rates were then correlated with elemental (C∶N and C∶P) and biochemical (sterol and fatty acid content) components of the food sources and clam tissue. Somatic growth rates were significantly higher when juveniles were fed eukaryotic algae than when fed cyanobacteria. Linear regression analyses revealed significant positive relationships between somatic growth rates and dietary sterol and polyunsaturated fatty acid content. Somatic growth rates also were highly correlated with the total sterol and α-linolenic acid content of clam tissues. This result suggests that the growth of C. fluminea is partially dependent on the availability of these essential lipids in the diet. Algal nutritional value may influence the successful geographic spread of this highly invasive species because food quality and quantity are changing as a result of global warming.
{"title":"Role of essential lipids in determining food quality for the invasive freshwater clam Corbicula fluminea","authors":"Timo Basen, D. Martin‐Creuzburg, K. Rothhaupt","doi":"10.1899/10-087.1","DOIUrl":"https://doi.org/10.1899/10-087.1","url":null,"abstract":"Abstract The invasive clam Corbicula fluminea has become a widespread benthic invertebrate in many freshwater ecosystems throughout Europe and North and South America. Invasive bivalves can dramatically alter the structure of native benthic communities, so understanding the factors responsible for successful invasion is important. We investigated C. fluminea nutritional requirements for essential lipids in a standardized growth experiment. Juvenile clams were fed different cyanobacteria (Aphanizomenon flos-aquae, Anabaena variabilis, Synechococcus elongatus) or eukaryotic algae (Scenedesmus obliquus, Cryptomonas sp.). Somatic growth rates were then correlated with elemental (C∶N and C∶P) and biochemical (sterol and fatty acid content) components of the food sources and clam tissue. Somatic growth rates were significantly higher when juveniles were fed eukaryotic algae than when fed cyanobacteria. Linear regression analyses revealed significant positive relationships between somatic growth rates and dietary sterol and polyunsaturated fatty acid content. Somatic growth rates also were highly correlated with the total sterol and α-linolenic acid content of clam tissues. This result suggests that the growth of C. fluminea is partially dependent on the availability of these essential lipids in the diet. Algal nutritional value may influence the successful geographic spread of this highly invasive species because food quality and quantity are changing as a result of global warming.","PeriodicalId":49987,"journal":{"name":"Journal of the North American Benthological Society","volume":"96 1","pages":"653 - 664"},"PeriodicalIF":0.0,"publicationDate":"2011-05-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83940477","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract The hyporheic zone is of great interest for stream ecologists because of its role in stream biogeochemical processing. Our study addresses the effects of leaf-litter inputs and varying discharge on surface–hyporheic water exchange and their possible consequences for the hyporheic zone biogeochemistry. Our study was conducted during autumn in Riera de Santa Fe (northeastern Iberian Peninsula), a stream with a well developed deciduous riparian canopy. We placed 15 wells spaced at 5-m intervals longitudinally down the study reach and measured surface and hyporheic nutrient and dissolved O2 (DO) concentrations on 23 sampling dates (15 during the leaffall period and 8 after a flood that washed out 65% of the accumulated leaf biomass). We assessed changes in surface-water exchange and in hyporheic NH4-N and soluble reactive P (SRP) uptake via coinjection of a conservative tracer and nutrients. Compared to surface water, hyporheic water had lower DO, higher SRP and NO3-N concentrations, and similar NH4-N concentration. Hyporheic water had higher DO saturation (p = 0.00) and higher NH4-N concentration (p = 0.00) in downwelling than in upwelling wells, whereas SRP and NO3-N concentrations did not differ significantly between well types (p > 0.05). Hydrologic connectivity was higher in downwelling than in upwelling wells and decreased with leaf-litter accumulation in the stream channel and increased with stream discharge. Increased connectivity after a flood reduced the difference in DO between surface and hyporheic compartments in upwelling and downwelling wells and in NO3-N in upwelling wells. NH4-N and SRP uptake responded differently to these changes. Hyporheic SRP uptake rate was controlled by hyporheic SRP concentration, which did not vary with changes in connectivity, whereas NH4-N uptake rate was indirectly affected by changes in connectivity through the influence of connectivity on DO availability. Last, although no NO3-N was added during the solute injections, we observed an increase in hyporheic NO3-N that probably was caused by nitrification. Together these results illustrate how the combination of stream hydrology and organic matter accumulation can dictate seasonal changes in hyporheic biogeochemistry.
潜流带在河流生物地球化学过程中起着重要的作用，引起了河流生态学家的极大兴趣。本研究探讨了凋落叶输入和不同排放对地表潜水交换的影响及其对潜水带生物地球化学的可能影响。我们的研究是在秋季在Riera de Santa Fe(伊比利亚半岛东北部)进行的，这是一条具有良好发育的落叶河岸树冠的河流。我们在研究河段纵向以5米间隔放置了15口井，并在23个采样日期(15个在叶片期，8个在洪水冲走65%的累积叶片生物量之后)测量了地表和地下营养物质和溶解氧(DO)的浓度。我们通过联合注射一种保守示踪剂和营养物来评估地表水交换、低渗NH4-N和可溶性反应性磷(SRP)摄取的变化。与地表水相比，低渗水的DO较低，SRP和NO3-N浓度较高，NH4-N浓度相近。下潜井的DO饱和度(p = 0.00)和NH4-N浓度(p = 0.00)高于上升井，而SRP和NO3-N浓度在不同井型间差异不显著(p > 0.05)。水文连通性随河道中枯叶枯落物的积累而降低，随河道流量的增加而增加。洪水后连通性的增加减少了上升流井和下升流井中地表和地下隔室之间的DO差异以及上升流井中NO3-N的差异。NH4-N和SRP摄取对这些变化的反应不同。而NH4-N的摄取速率则通过连通性对DO有效性的影响而间接受到连通性变化的影响。最后，虽然在溶质注入过程中没有添加NO3-N，但我们观察到低渗NO3-N的增加，这可能是由硝化作用引起的。综上所述，这些结果说明了河流水文和有机质积累的结合如何决定了潜流生物地球化学的季节变化。
{"title":"Temporal variation of hydrological exchange and hyporheic biogeochemistry in a headwater stream during autumn","authors":"A. Argerich, E. Martí, F. Sabater, M. Ribot","doi":"10.1899/10-078.1","DOIUrl":"https://doi.org/10.1899/10-078.1","url":null,"abstract":"Abstract The hyporheic zone is of great interest for stream ecologists because of its role in stream biogeochemical processing. Our study addresses the effects of leaf-litter inputs and varying discharge on surface–hyporheic water exchange and their possible consequences for the hyporheic zone biogeochemistry. Our study was conducted during autumn in Riera de Santa Fe (northeastern Iberian Peninsula), a stream with a well developed deciduous riparian canopy. We placed 15 wells spaced at 5-m intervals longitudinally down the study reach and measured surface and hyporheic nutrient and dissolved O2 (DO) concentrations on 23 sampling dates (15 during the leaffall period and 8 after a flood that washed out 65% of the accumulated leaf biomass). We assessed changes in surface-water exchange and in hyporheic NH4-N and soluble reactive P (SRP) uptake via coinjection of a conservative tracer and nutrients. Compared to surface water, hyporheic water had lower DO, higher SRP and NO3-N concentrations, and similar NH4-N concentration. Hyporheic water had higher DO saturation (p = 0.00) and higher NH4-N concentration (p = 0.00) in downwelling than in upwelling wells, whereas SRP and NO3-N concentrations did not differ significantly between well types (p > 0.05). Hydrologic connectivity was higher in downwelling than in upwelling wells and decreased with leaf-litter accumulation in the stream channel and increased with stream discharge. Increased connectivity after a flood reduced the difference in DO between surface and hyporheic compartments in upwelling and downwelling wells and in NO3-N in upwelling wells. NH4-N and SRP uptake responded differently to these changes. Hyporheic SRP uptake rate was controlled by hyporheic SRP concentration, which did not vary with changes in connectivity, whereas NH4-N uptake rate was indirectly affected by changes in connectivity through the influence of connectivity on DO availability. Last, although no NO3-N was added during the solute injections, we observed an increase in hyporheic NO3-N that probably was caused by nitrification. Together these results illustrate how the combination of stream hydrology and organic matter accumulation can dictate seasonal changes in hyporheic biogeochemistry.","PeriodicalId":49987,"journal":{"name":"Journal of the North American Benthological Society","volume":"55 1","pages":"635 - 652"},"PeriodicalIF":0.0,"publicationDate":"2011-05-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85008910","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract We examined latitudinal patterns of generic richness in stream insects across the Mackenzie River system in northern Canada. We focused on low- to mid-order tributaries flowing into the river and spanning ∼11° of latitude. Physical-habitat characteristics and water chemistry were examined as factors affecting diversity both at the local and regional scale. No overall latitudinal trend was found in richness, but trends were apparent at the order level. Local generic richness of Ephemeroptera and Plecoptera declined toward the north, Trichoptera generic richness was lowest in the middle of the latitudinal range, and Diptera generic richness increased with latitude. Most orders of aquatic insects followed the expected decline in richness with increasing latitude, but the family Chironomidae was an exception, probably because of their ability to tolerate subarctic environmental conditions and because of the relative absence of potential predation and competition from other invertebrates. Streams were characterized along principal component axes corresponding to stream size and terrain, substrate, water source, and turbidity. Most groups were slightly more diverse in larger streams. Ephemeroptera and Plecoptera had higher richness on coarse substrates, and Trichoptera had lower richness in streams in the Norman Range that possessed unique hydrology and water-chemistry characteristics because of the presence of taliks. Chironomid richness was positively correlated with latitude and stream size. Latitudinal gradients in regional diversity largely followed the trends in local richness, but all taxa had small regional numbers of genera near the middle of the latitudinal range, and a decline in overall aquatic insect richness between the south and north was more apparent at the regional scale. We conclude that regional environmental factors control the maximum richness that can be expected in a locality at a given latitude, whereas local environmental factors control the number of taxa present at a site. Spatial gradients in benthic insect richness are likely to affect the applicability of biomonitoring metrics that use groups whose richness varies with latitude.
{"title":"Latitudinal gradients and local control of aquatic insect richness in a large river system in northern Canada","authors":"Ryan W. Scott, D. Barton, M. Evans, J. Keating","doi":"10.1899/10-112.1","DOIUrl":"https://doi.org/10.1899/10-112.1","url":null,"abstract":"Abstract We examined latitudinal patterns of generic richness in stream insects across the Mackenzie River system in northern Canada. We focused on low- to mid-order tributaries flowing into the river and spanning ∼11° of latitude. Physical-habitat characteristics and water chemistry were examined as factors affecting diversity both at the local and regional scale. No overall latitudinal trend was found in richness, but trends were apparent at the order level. Local generic richness of Ephemeroptera and Plecoptera declined toward the north, Trichoptera generic richness was lowest in the middle of the latitudinal range, and Diptera generic richness increased with latitude. Most orders of aquatic insects followed the expected decline in richness with increasing latitude, but the family Chironomidae was an exception, probably because of their ability to tolerate subarctic environmental conditions and because of the relative absence of potential predation and competition from other invertebrates. Streams were characterized along principal component axes corresponding to stream size and terrain, substrate, water source, and turbidity. Most groups were slightly more diverse in larger streams. Ephemeroptera and Plecoptera had higher richness on coarse substrates, and Trichoptera had lower richness in streams in the Norman Range that possessed unique hydrology and water-chemistry characteristics because of the presence of taliks. Chironomid richness was positively correlated with latitude and stream size. Latitudinal gradients in regional diversity largely followed the trends in local richness, but all taxa had small regional numbers of genera near the middle of the latitudinal range, and a decline in overall aquatic insect richness between the south and north was more apparent at the regional scale. We conclude that regional environmental factors control the maximum richness that can be expected in a locality at a given latitude, whereas local environmental factors control the number of taxa present at a site. Spatial gradients in benthic insect richness are likely to affect the applicability of biomonitoring metrics that use groups whose richness varies with latitude.","PeriodicalId":49987,"journal":{"name":"Journal of the North American Benthological Society","volume":"50 1","pages":"621 - 634"},"PeriodicalIF":0.0,"publicationDate":"2011-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79174278","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract The temporal pattern of river metabolism was estimated for high-order rivers (5–7th) in the Daly watershed, tropical Australia, during the dry season (May–October) when discharge was supplied predominantly by groundwater. Rates of photosynthesis (P) and respiration (R) were calculated at 4 sites using the open-channel method based on a model of the river's O2 budget and measured diurnal cycles of dissolved O2 concentrations and temperatures. The rivers were shallow (average depth = 0.8 m), clear (1–2 NTU), and had low concentrations of nutrients (≤15 µg/L soluble N and P at most sites) and generally open canopy. At the reach scale, P was limited by light with no evidence of light saturation. An increase in primary producer biomass over the dry season probably underpinned an approximate doubling of P at the 4 sites over the dry season, but increased water temperatures would have contributed, too. P (0.1–4.6 g O2 m−2 d−1) in the Daly watershed was similar to rates in a shaded tropical Puerto Rican stream and some temperate rivers but was lower than in nutrient-enriched temperate rivers. We surmise that most P resulted in production of dissolved organic C (DOC), rather than growth of primary producer biomass, which was nutrient limited. R exceeded P (P/R ≈ 0.5), and increased approximately linearly with P (r2 = 0.79–0.99) over the dry season with no statistically significant difference among sites. The similar environmental setting of the 4 sites underpinned their similar temporal pattern of metabolism. Bacterial metabolism of photosynthetically produced DOC (PDOC) could partially explain the tight coupling of R and P but could not account for the river's overall net heterotrophy. The priming effect of bacterial degradation of labile PDOC to increase the mineralization of recalcitrant DOC (e.g., humic acids) provides an explanation for the river's heterotrophy and tight coupling between P and R.
{"title":"Metabolism in a groundwater-fed river system in the Australian wet/dry tropics: tight coupling of photosynthesis and respiration","authors":"S. Townsend, I. Webster, J. Schult","doi":"10.1899/10-066.1","DOIUrl":"https://doi.org/10.1899/10-066.1","url":null,"abstract":"Abstract The temporal pattern of river metabolism was estimated for high-order rivers (5–7th) in the Daly watershed, tropical Australia, during the dry season (May–October) when discharge was supplied predominantly by groundwater. Rates of photosynthesis (P) and respiration (R) were calculated at 4 sites using the open-channel method based on a model of the river's O2 budget and measured diurnal cycles of dissolved O2 concentrations and temperatures. The rivers were shallow (average depth = 0.8 m), clear (1–2 NTU), and had low concentrations of nutrients (≤15 µg/L soluble N and P at most sites) and generally open canopy. At the reach scale, P was limited by light with no evidence of light saturation. An increase in primary producer biomass over the dry season probably underpinned an approximate doubling of P at the 4 sites over the dry season, but increased water temperatures would have contributed, too. P (0.1–4.6 g O2 m−2 d−1) in the Daly watershed was similar to rates in a shaded tropical Puerto Rican stream and some temperate rivers but was lower than in nutrient-enriched temperate rivers. We surmise that most P resulted in production of dissolved organic C (DOC), rather than growth of primary producer biomass, which was nutrient limited. R exceeded P (P/R ≈ 0.5), and increased approximately linearly with P (r2 = 0.79–0.99) over the dry season with no statistically significant difference among sites. The similar environmental setting of the 4 sites underpinned their similar temporal pattern of metabolism. Bacterial metabolism of photosynthetically produced DOC (PDOC) could partially explain the tight coupling of R and P but could not account for the river's overall net heterotrophy. The priming effect of bacterial degradation of labile PDOC to increase the mineralization of recalcitrant DOC (e.g., humic acids) provides an explanation for the river's heterotrophy and tight coupling between P and R.","PeriodicalId":49987,"journal":{"name":"Journal of the North American Benthological Society","volume":"46 1","pages":"603 - 620"},"PeriodicalIF":0.0,"publicationDate":"2011-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89978196","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract We evaluated the potential of habitat restoration to improve stream and riparian habitat and to minimize the prevalence of whirling disease in a population of native cutthroat trout in northern Utah. We fenced 67 ha of riparian habitat to exclude livestock and measured key response variables at impact and control sites before and after the completion of the exclosure. Total N concentrations decreased in response to the exclusion. Over this short time period (1–2 y postrestoration), the combination of natural variability and exclusion of livestock grazing appeared to alter the vegetation and riparian conditions through increased bank stability and decreased % cover of exotic plant species. The effect of the exclosure on whirling disease was confounded by climatic variation. However, restoration appeared to reduce the prevalence of whirling disease during a nondrought year, but not during a drought year. Therefore, in the short term, these beneficial effects of restoration on trout appeared to hinge on favorable climatic conditions. We expect the longer-term restoration response to be affected less than the short-term response by climatic conditions. The results of our study indicate that passive stream restoration is an effective management approach for restoring stream habitat and has the potential to minimize interactive effects of disease and habitat degradation, especially when other options for disease management are not possible or practical.
{"title":"The potential of passive stream restoration to improve stream habitat and minimize the impact of fish disease: a short-term assessment","authors":"E. Hansen, P. Budy","doi":"10.1899/10-018.1","DOIUrl":"https://doi.org/10.1899/10-018.1","url":null,"abstract":"Abstract We evaluated the potential of habitat restoration to improve stream and riparian habitat and to minimize the prevalence of whirling disease in a population of native cutthroat trout in northern Utah. We fenced 67 ha of riparian habitat to exclude livestock and measured key response variables at impact and control sites before and after the completion of the exclosure. Total N concentrations decreased in response to the exclusion. Over this short time period (1–2 y postrestoration), the combination of natural variability and exclusion of livestock grazing appeared to alter the vegetation and riparian conditions through increased bank stability and decreased % cover of exotic plant species. The effect of the exclosure on whirling disease was confounded by climatic variation. However, restoration appeared to reduce the prevalence of whirling disease during a nondrought year, but not during a drought year. Therefore, in the short term, these beneficial effects of restoration on trout appeared to hinge on favorable climatic conditions. We expect the longer-term restoration response to be affected less than the short-term response by climatic conditions. The results of our study indicate that passive stream restoration is an effective management approach for restoring stream habitat and has the potential to minimize interactive effects of disease and habitat degradation, especially when other options for disease management are not possible or practical.","PeriodicalId":49987,"journal":{"name":"Journal of the North American Benthological Society","volume":"1 1","pages":"573 - 588"},"PeriodicalIF":0.0,"publicationDate":"2011-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83690135","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract Great Plains rivers are characterized by unpredictable, thunderstorm-generated flow events that can abruptly restructure their physical complexity. These morphodynamic disturbances force river organisms to overcome hydrologic challenges. Some organisms surmount these challenges by using refugia, which play a key role in the ecological processes that govern lotic systems. The physical complexity of rivers can determine the availability and diversity of refugia both within and among rivers. However, physical complexity often changes with the hydrologic cycle and position along the river. We determined how the benthic community was affected by changes in the structure and abundance of in-channel refugia created by hydrologic fluctuations. We worked on and around sandbars in the Kansas River (Kaw), a multithread, sand-bed river. The composition of the zoobenthic community was directly related to the complexity of river morphology and flow rates. The community of 1 side channel consistently shifted over time between 2 distinct assemblages depending on whether the side channel was flowing or a disconnected slackwater. The benthic invertebrate community exploits many strategies to survive in the abrasive and continually fluctuating Kaw, including using sandbars as refugia and places for recolonization. The refuge provided by these sandbars will become increasingly important in the future if precipitation regimes become more variable as predicted by climate-change scenarios for the region. However, increased levee and dam construction threaten the persistence of the sandbars and vital habitats that they create.
{"title":"Flow refugia for the zoobenthos of a sand-bed river: the role of physical-habitat complexity","authors":"B. J. O’Neill, J. Thorp","doi":"10.1899/10-083.1","DOIUrl":"https://doi.org/10.1899/10-083.1","url":null,"abstract":"Abstract Great Plains rivers are characterized by unpredictable, thunderstorm-generated flow events that can abruptly restructure their physical complexity. These morphodynamic disturbances force river organisms to overcome hydrologic challenges. Some organisms surmount these challenges by using refugia, which play a key role in the ecological processes that govern lotic systems. The physical complexity of rivers can determine the availability and diversity of refugia both within and among rivers. However, physical complexity often changes with the hydrologic cycle and position along the river. We determined how the benthic community was affected by changes in the structure and abundance of in-channel refugia created by hydrologic fluctuations. We worked on and around sandbars in the Kansas River (Kaw), a multithread, sand-bed river. The composition of the zoobenthic community was directly related to the complexity of river morphology and flow rates. The community of 1 side channel consistently shifted over time between 2 distinct assemblages depending on whether the side channel was flowing or a disconnected slackwater. The benthic invertebrate community exploits many strategies to survive in the abrasive and continually fluctuating Kaw, including using sandbars as refugia and places for recolonization. The refuge provided by these sandbars will become increasingly important in the future if precipitation regimes become more variable as predicted by climate-change scenarios for the region. However, increased levee and dam construction threaten the persistence of the sandbars and vital habitats that they create.","PeriodicalId":49987,"journal":{"name":"Journal of the North American Benthological Society","volume":"53 1","pages":"546 - 558"},"PeriodicalIF":0.0,"publicationDate":"2011-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87108968","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Baozhu Pan, Haijun Wang, Xiao-min Liang, Hongzhn Wang
Abstract A systematic investigation of macrozoobenthos was conducted in Yangtze floodplain waters to reveal patterns of density, biomass, and production in relation to river connectivity. In the Yangtze-connected lakes, 78 taxa belonging to 33 families and 62 genera were identified. Macrozoobenthos density was 327 individuals/m2, biomass was 1.40 g dry mass/m2, and production was 3.23 g dry mass m−2 y−1. The assemblages were characterized by high diversity, high production, and high bivalve-filterer abundance. The key factor determining the macrozoobenthic assemblages was river connectivity. As river connectivity increased, 3 types of response patterns were observed: 1) density, biomass, and production of collector-filterers (mainly Bivalvia), shredders (e.g., Stictochironomus), and predators (e.g., Dytiscidae) showed unimodal changes, i.e., first increased and then decreased; 2) density, biomass, and production of collector-gatherers (mainly Tubificidae and Chironomidae) decreased continuously; and 3) density of scrapers (mainly Gastropoda) decreased, whereas their biomass and production changed unimodally. At an intermediate level of river connectivity, biomass and production of total macrozoobenthos reached maxima, whereas density decreased with increasing river connectivity. Previous research showed that α diversity of zoobenthos also peaks at moderate connectivity with rivers. Therefore, to maintain high productivity as well as high biodiversity in the Yangtze floodplain, protecting the remnants of river-connected lakes and linking disconnected lakes freely with the mainstream are crucial.
{"title":"Macrozoobenthos in Yangtze floodplain lakes: patterns of density, biomass, and production in relation to river connectivity","authors":"Baozhu Pan, Haijun Wang, Xiao-min Liang, Hongzhn Wang","doi":"10.1899/10-025.1","DOIUrl":"https://doi.org/10.1899/10-025.1","url":null,"abstract":"Abstract A systematic investigation of macrozoobenthos was conducted in Yangtze floodplain waters to reveal patterns of density, biomass, and production in relation to river connectivity. In the Yangtze-connected lakes, 78 taxa belonging to 33 families and 62 genera were identified. Macrozoobenthos density was 327 individuals/m2, biomass was 1.40 g dry mass/m2, and production was 3.23 g dry mass m−2 y−1. The assemblages were characterized by high diversity, high production, and high bivalve-filterer abundance. The key factor determining the macrozoobenthic assemblages was river connectivity. As river connectivity increased, 3 types of response patterns were observed: 1) density, biomass, and production of collector-filterers (mainly Bivalvia), shredders (e.g., Stictochironomus), and predators (e.g., Dytiscidae) showed unimodal changes, i.e., first increased and then decreased; 2) density, biomass, and production of collector-gatherers (mainly Tubificidae and Chironomidae) decreased continuously; and 3) density of scrapers (mainly Gastropoda) decreased, whereas their biomass and production changed unimodally. At an intermediate level of river connectivity, biomass and production of total macrozoobenthos reached maxima, whereas density decreased with increasing river connectivity. Previous research showed that α diversity of zoobenthos also peaks at moderate connectivity with rivers. Therefore, to maintain high productivity as well as high biodiversity in the Yangtze floodplain, protecting the remnants of river-connected lakes and linking disconnected lakes freely with the mainstream are crucial.","PeriodicalId":49987,"journal":{"name":"Journal of the North American Benthological Society","volume":"56 1","pages":"589 - 602"},"PeriodicalIF":0.0,"publicationDate":"2011-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77494115","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract Stream ecosystems receive and transport nutrients from terrestrial ecosystems and are important sites of N retention and removal in catchments. Many streams experience high anthropogenic N loading, which can overwhelm N retention and removal mechanisms and cause large downstream fluxes. Small, headwater streams are important sites of N retention, but the role of streams in larger catchments or as discharge increases is less clear. We evaluated how NO3− uptake dynamics responded to chronic N loading at different sites in a river draining a large desert catchment (∼7600 km2). Based on nutrient saturation theory, we predicted that chronic N loading would result in decreased uptake efficiency. Previous research suggested that increasing stream discharge also is associated with decreasing N-uptake efficiency. We addressed these relationships for a desert river by examining NO3− uptake dynamics over variable stream discharge encompassing its long-term range in base flow. We used short-term nutrient-addition studies to estimate uptake parameters for NO3− in a reference reach and a reach subject to chronic NO3− input. NO3− uptake efficiency was lower in the N-enriched reach than in the reference reach. However, within a reach, temporal changes in discharge and N concentration did not always affect uptake efficiency as predicted; e.g., pulses of high N flux following monsoon-season flooding did not result in reduced uptake efficiency. Estimates of denitrification rates indicated that this N-removal process was only a small fraction of N uptake, a result suggesting that most N is temporarily retained and eventually is exported downstream. N concentration exerted the primary influence on NO3− uptake efficiency in this large desert stream. However, within reaches, other factors that influence N retention, including floods, biota, and variable flow paths, probably contributed to observed temporal variation.
{"title":"Chronic N loading reduces N retention across varying base flows in a desert river","authors":"Rebecca A. Martin, T. Harms, N. Grimm","doi":"10.1899/09-137.1","DOIUrl":"https://doi.org/10.1899/09-137.1","url":null,"abstract":"Abstract Stream ecosystems receive and transport nutrients from terrestrial ecosystems and are important sites of N retention and removal in catchments. Many streams experience high anthropogenic N loading, which can overwhelm N retention and removal mechanisms and cause large downstream fluxes. Small, headwater streams are important sites of N retention, but the role of streams in larger catchments or as discharge increases is less clear. We evaluated how NO3− uptake dynamics responded to chronic N loading at different sites in a river draining a large desert catchment (∼7600 km2). Based on nutrient saturation theory, we predicted that chronic N loading would result in decreased uptake efficiency. Previous research suggested that increasing stream discharge also is associated with decreasing N-uptake efficiency. We addressed these relationships for a desert river by examining NO3− uptake dynamics over variable stream discharge encompassing its long-term range in base flow. We used short-term nutrient-addition studies to estimate uptake parameters for NO3− in a reference reach and a reach subject to chronic NO3− input. NO3− uptake efficiency was lower in the N-enriched reach than in the reference reach. However, within a reach, temporal changes in discharge and N concentration did not always affect uptake efficiency as predicted; e.g., pulses of high N flux following monsoon-season flooding did not result in reduced uptake efficiency. Estimates of denitrification rates indicated that this N-removal process was only a small fraction of N uptake, a result suggesting that most N is temporarily retained and eventually is exported downstream. N concentration exerted the primary influence on NO3− uptake efficiency in this large desert stream. However, within reaches, other factors that influence N retention, including floods, biota, and variable flow paths, probably contributed to observed temporal variation.","PeriodicalId":49987,"journal":{"name":"Journal of the North American Benthological Society","volume":"2001 1","pages":"559 - 572"},"PeriodicalIF":0.0,"publicationDate":"2011-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72786180","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract In this experimental study, conducted in coastal Oregon USA, we examined how small increases in summer water temperatures affected aquatic insect growth and autumn emergence. We maintained naturally fluctuating temperatures from 2 nearby streams and a 3rd regime, naturally fluctuating temperatures warmed by 3–5°C, in flow-through troughs from mid-summer until autumn. We added selected abundant Ephemeroptera, Plecoptera, and Trichoptera species to the 3 treatments in late July and observed emergence until early December. We described the taxon-specific responses of the caddisfly Psychoglypha bella and the mayfly Paraleptophlebia bicornuta, both of which survived well in the troughs (67–86%), and the stonefly Mesocapnia projecta, which we did not collect in mid-summer but had colonized all experimental troughs by October. We observed primarily phenological rather than morphological responses to higher water temperatures. The most synchronous emergence of male and female P. bella and P. bicornuta occurred in the trough with the coolest temperatures. Only P. bella emerged asynchronously from the trough with the warmest temperatures. The decreases in synchrony were largely the result of earlier emergence of males. Paraleptophlebia bicornuta were larger and tended towards asynchrony in the trough with water (and temperatures) from their natal stream. Individuals in the trough with the warmest temperature were smaller than individuals in other troughs, but did not emerge earlier. Mesocapnia projecta showed greater synchrony in emergence, which occurred over a shorter interval, than the other species. When exposed to increased water temperatures, autumn-emergent taxa may be most vulnerable to trade-offs between asynchronous emergence and the probabilities for finding mates in unpredictable weather conditions.
{"title":"Three responses to small changes in stream temperature by autumn-emerging aquatic insects","authors":"Judith L. Li, S. Johnson, Janel Banks Sobota","doi":"10.1899/10-024.1","DOIUrl":"https://doi.org/10.1899/10-024.1","url":null,"abstract":"Abstract In this experimental study, conducted in coastal Oregon USA, we examined how small increases in summer water temperatures affected aquatic insect growth and autumn emergence. We maintained naturally fluctuating temperatures from 2 nearby streams and a 3rd regime, naturally fluctuating temperatures warmed by 3–5°C, in flow-through troughs from mid-summer until autumn. We added selected abundant Ephemeroptera, Plecoptera, and Trichoptera species to the 3 treatments in late July and observed emergence until early December. We described the taxon-specific responses of the caddisfly Psychoglypha bella and the mayfly Paraleptophlebia bicornuta, both of which survived well in the troughs (67–86%), and the stonefly Mesocapnia projecta, which we did not collect in mid-summer but had colonized all experimental troughs by October. We observed primarily phenological rather than morphological responses to higher water temperatures. The most synchronous emergence of male and female P. bella and P. bicornuta occurred in the trough with the coolest temperatures. Only P. bella emerged asynchronously from the trough with the warmest temperatures. The decreases in synchrony were largely the result of earlier emergence of males. Paraleptophlebia bicornuta were larger and tended towards asynchrony in the trough with water (and temperatures) from their natal stream. Individuals in the trough with the warmest temperature were smaller than individuals in other troughs, but did not emerge earlier. Mesocapnia projecta showed greater synchrony in emergence, which occurred over a shorter interval, than the other species. When exposed to increased water temperatures, autumn-emergent taxa may be most vulnerable to trade-offs between asynchronous emergence and the probabilities for finding mates in unpredictable weather conditions.","PeriodicalId":49987,"journal":{"name":"Journal of the North American Benthological Society","volume":"7 1","pages":"474 - 484"},"PeriodicalIF":0.0,"publicationDate":"2011-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74486281","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract The decline of freshwater mussels in the southeastern US emphasizes the need to evaluate the current status of mussel populations. We used the Robust Design, which is a capture–recapture sampling design, to estimate demographic parameters (apparent survival and temporary emigration) and capture probabilities of Alasmidonta arcula, Lampsilis dolabraeformis, Lampsilis splendida, and Pyganodon gibbosa in a large lowland river in Georgia. Mussels were sampled in individual habitat units using line-transect methods at ∼6-wk intervals from summer 2006–2007. We used an information-theoretic approach to evaluate the relative importance of maximum river discharge, habitat characteristics, mussel species, and season on temporary emigration (i.e., proportion of mussels not at the surface), apparent survival, and capture probability. The best-supported models indicated that apparent survival and capture probability varied positively with mussel shell length and among habitat types. Apparent survival (6-wk interval) ranged from 94 to 99% and was greatest in slackwater and lowest in swiftwater habitat. Capture probability ranged from 8 to 20% and was greatest in slackwater and lowest in swiftwater habitat. Temporary emigration also varied among species and season and appeared to be related to reproductive behavior, with the largest proportion of mussels occurring at the surface when mussels appeared to be reproductively active. A comparison of catch-per-unit-effort indices to population estimates suggested that the reliability of catch-per-unit-effort indices was influenced by vertical migration behavior and other factors affecting mussel capture probability.
{"title":"An evaluation of the factors influencing freshwater mussel capture probability, survival, and temporary emigration in a large lowland river","authors":"Jason Meador, J. Peterson, J. M. Wisniewski","doi":"10.1899/10-105.1","DOIUrl":"https://doi.org/10.1899/10-105.1","url":null,"abstract":"Abstract The decline of freshwater mussels in the southeastern US emphasizes the need to evaluate the current status of mussel populations. We used the Robust Design, which is a capture–recapture sampling design, to estimate demographic parameters (apparent survival and temporary emigration) and capture probabilities of Alasmidonta arcula, Lampsilis dolabraeformis, Lampsilis splendida, and Pyganodon gibbosa in a large lowland river in Georgia. Mussels were sampled in individual habitat units using line-transect methods at ∼6-wk intervals from summer 2006–2007. We used an information-theoretic approach to evaluate the relative importance of maximum river discharge, habitat characteristics, mussel species, and season on temporary emigration (i.e., proportion of mussels not at the surface), apparent survival, and capture probability. The best-supported models indicated that apparent survival and capture probability varied positively with mussel shell length and among habitat types. Apparent survival (6-wk interval) ranged from 94 to 99% and was greatest in slackwater and lowest in swiftwater habitat. Capture probability ranged from 8 to 20% and was greatest in slackwater and lowest in swiftwater habitat. Temporary emigration also varied among species and season and appeared to be related to reproductive behavior, with the largest proportion of mussels occurring at the surface when mussels appeared to be reproductively active. A comparison of catch-per-unit-effort indices to population estimates suggested that the reliability of catch-per-unit-effort indices was influenced by vertical migration behavior and other factors affecting mussel capture probability.","PeriodicalId":49987,"journal":{"name":"Journal of the North American Benthological Society","volume":"195 1","pages":"507 - 521"},"PeriodicalIF":0.0,"publicationDate":"2011-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77711187","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：