D. Nakano, Tomoya Iwata, Jumpei Suzuki, Teruhisa Okada, Ryosuke Yamamoto, M. Imamura
Ecosystem metabolism is a fundamental process that governs biogeochemical C cycling through the fixation and mineralization of C by all the organisms in a system; however, the functional responses of ecosystem metabolism to light and temperature variability remain unknown in streams and rivers. In this study, we assessed the effects of temperature and light on ecosystem metabolism, namely gross primary production (GPP) and ecosystem respiration (ER), in a Japanese stream by monitoring the seasonal diel changes in dissolved oxygen. We found that the temperature dependence of metabolism, which is expressed as activation energy, was higher for ER (0.48 eV) than for GPP (0.39 eV), supporting the metabolic theory of ecology. Both daily GPP and ER increased with the daily integrated photosynthetically active radiation (PAR), peaking at moderate PAR values and decreasing at higher irradiance levels. This unimodal relationship between daily GPP and PAR was due to the rapid increase of instantaneous PAR during the early morning, suppressing the maximum rate of area-specific productivity, which was a main determinant of daily GPP. Moreover, daily GPP and ER were closely associated in this study stream, resulting in a unimodal pattern of daily ER with daily integrated PAR. Our results suggest that both temperature and light regulate stream ecosystem metabolism but that the sunlight regime (i.e., the rapid increase of solar irradiance in the early morning) rather than light intensity per se may be a critical factor for both GPP and ER in the study stream.
{"title":"The effects of temperature and light on ecosystem metabolism in a Japanese stream","authors":"D. Nakano, Tomoya Iwata, Jumpei Suzuki, Teruhisa Okada, Ryosuke Yamamoto, M. Imamura","doi":"10.1086/718648","DOIUrl":"https://doi.org/10.1086/718648","url":null,"abstract":"Ecosystem metabolism is a fundamental process that governs biogeochemical C cycling through the fixation and mineralization of C by all the organisms in a system; however, the functional responses of ecosystem metabolism to light and temperature variability remain unknown in streams and rivers. In this study, we assessed the effects of temperature and light on ecosystem metabolism, namely gross primary production (GPP) and ecosystem respiration (ER), in a Japanese stream by monitoring the seasonal diel changes in dissolved oxygen. We found that the temperature dependence of metabolism, which is expressed as activation energy, was higher for ER (0.48 eV) than for GPP (0.39 eV), supporting the metabolic theory of ecology. Both daily GPP and ER increased with the daily integrated photosynthetically active radiation (PAR), peaking at moderate PAR values and decreasing at higher irradiance levels. This unimodal relationship between daily GPP and PAR was due to the rapid increase of instantaneous PAR during the early morning, suppressing the maximum rate of area-specific productivity, which was a main determinant of daily GPP. Moreover, daily GPP and ER were closely associated in this study stream, resulting in a unimodal pattern of daily ER with daily integrated PAR. Our results suggest that both temperature and light regulate stream ecosystem metabolism but that the sunlight regime (i.e., the rapid increase of solar irradiance in the early morning) rather than light intensity per se may be a critical factor for both GPP and ER in the study stream.","PeriodicalId":48926,"journal":{"name":"Freshwater Science","volume":"41 1","pages":"113 - 124"},"PeriodicalIF":1.8,"publicationDate":"2021-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44045016","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Juliana S. Leal, Angélica L. González, Rhuana C. Paulo, V. Farjalla
Autochthonous biomass is heterogeneously distributed within freshwater ecosystems, shaping community structure and ecosystem functioning, yet few studies have evaluated how the spatial heterogeneity in the availability of the autochthonous resource affects its contribution to the diets of aquatic consumers. To fill this gap, we conducted a field survey to test whether the spatial heterogeneity of the autochthonous resource within freshwater ecosystems formed in tank bromeliads determines its contribution to the diet of aquatic consumers. Tank bromeliads are Neotropical plants with densely arranged leaves in a rosette shape that accumulate rainwater and terrestrial plant material, providing suitable habitat for a diversity of aquatic invertebrates. We sampled 3 regions (north, central, and south) of the bromeliad ecosystem to provide a natural gradient in the availability of the autochthonous resource (i.e., algae biomass). To trace the diets of aquatic consumers, we used stable isotope analysis of hydrogen coupled with Bayesian stable isotope mixing models. The availability of the autochthonous resource varied among the tank-bromeliad regions with light availability, but it was not related to its relative contribution to the diets of aquatic consumers. Instead, aquatic consumers from all regions showed similarly high degrees of autochthony. The capacity of aquatic consumers to move within the plant did not affect the contribution of the autochthonous resource to their diets. We reason that the contribution of the autochthonous resource to the diets of consumers is not related to its spatial distribution because aquatic consumers preferentially feed on this resource, even when its stocks are limited. In addition, water flow among tanks could provide a subsidy of the autochthonous resource from more productive to less productive regions. We conclude that spatial heterogeneity in the availability of the autochthonous resource does not limit its contribution to the diet of aquatic consumers because of active foraging on the autochthonous resource and the flux of this resource among compartments in freshwater tank-bromeliad ecosystems.
{"title":"The contribution of autochthonous resource to the diet of aquatic consumers is unrelated to its spatial distribution in tank bromeliads","authors":"Juliana S. Leal, Angélica L. González, Rhuana C. Paulo, V. Farjalla","doi":"10.1086/718630","DOIUrl":"https://doi.org/10.1086/718630","url":null,"abstract":"Autochthonous biomass is heterogeneously distributed within freshwater ecosystems, shaping community structure and ecosystem functioning, yet few studies have evaluated how the spatial heterogeneity in the availability of the autochthonous resource affects its contribution to the diets of aquatic consumers. To fill this gap, we conducted a field survey to test whether the spatial heterogeneity of the autochthonous resource within freshwater ecosystems formed in tank bromeliads determines its contribution to the diet of aquatic consumers. Tank bromeliads are Neotropical plants with densely arranged leaves in a rosette shape that accumulate rainwater and terrestrial plant material, providing suitable habitat for a diversity of aquatic invertebrates. We sampled 3 regions (north, central, and south) of the bromeliad ecosystem to provide a natural gradient in the availability of the autochthonous resource (i.e., algae biomass). To trace the diets of aquatic consumers, we used stable isotope analysis of hydrogen coupled with Bayesian stable isotope mixing models. The availability of the autochthonous resource varied among the tank-bromeliad regions with light availability, but it was not related to its relative contribution to the diets of aquatic consumers. Instead, aquatic consumers from all regions showed similarly high degrees of autochthony. The capacity of aquatic consumers to move within the plant did not affect the contribution of the autochthonous resource to their diets. We reason that the contribution of the autochthonous resource to the diets of consumers is not related to its spatial distribution because aquatic consumers preferentially feed on this resource, even when its stocks are limited. In addition, water flow among tanks could provide a subsidy of the autochthonous resource from more productive to less productive regions. We conclude that spatial heterogeneity in the availability of the autochthonous resource does not limit its contribution to the diet of aquatic consumers because of active foraging on the autochthonous resource and the flux of this resource among compartments in freshwater tank-bromeliad ecosystems.","PeriodicalId":48926,"journal":{"name":"Freshwater Science","volume":"41 1","pages":"77 - 87"},"PeriodicalIF":1.8,"publicationDate":"2021-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43568571","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Large-scale disturbances, such as wildfire, can markedly affect streams for years. As terrestrial areas within a watershed slowly recover, stream environments and biota can experience repeated and long-lasting challenges. In 2011, the Las Conchas wildfire burned 1/3 of the Valles Caldera National Preserve in northern New Mexico, USA. Seven y post-fire, streams located near the burn perimeter continue to experience varying levels of alteration (e.g., channel alteration with large diel temperature swings), whereas the terrestrial uplands have begun to recover. Extreme temperatures in stream systems may affect the aquatic community, including ectotherms such as caddisflies. These post-fire temperature ranges may increase an ectotherm’s breadth of thermal adaptation, but at metabolic costs that diminish organismal performance, such as growth, development, and fecundity. In this study we characterized in-situ effects of varied thermal regimes across preserve streams on the performance of the caddisfly Hydropsyche oslari Banks, 1905. We measured mass and critical thermal maximum (CTmax) in H. oslari larvae from preserve streams affected by wildfire (high temperature range) and in streams minimally affected by wildfire (low temperature range). We predicted that increased daily temperature maxima and reduced daily temperature minima (i.e., large diel temperature swings) would be associated with reduced H. oslari mass because of the limiting effects of suboptimal temperatures on growth. As predicted, in the weeks prior to their emergence as terrestrial adults, 5th-instar larvae within the high-temperature range stream had reduced mass (mean 3.3 ± SE 0.55 mg) relative to larvae from the low-temperature range stream (6.2 ± 0.69 mg). We also predicted that CTmax of H. oslari would reflect stream thermal history. Indeed, larvae H. oslari from the high-temperature range stream exhibited increased CTmax (35.4 ± 0.17°C) compared with larvae from the low-temperature range stream (34.4 ± 0.28°C). We demonstrated that the effects of wildfire on caddisflies can be long lasting, as evidenced by the reduced size at maturity and higher thermal tolerance in a caddisfly population 7 y post-fire.
{"title":"Wildfire effects on mass and thermal tolerance of Hydropsyche oslari (Trichoptera) in southwestern USA montane grassland streams","authors":"Lauren B. Kremer, C. Caldwell","doi":"10.1086/718556","DOIUrl":"https://doi.org/10.1086/718556","url":null,"abstract":"Large-scale disturbances, such as wildfire, can markedly affect streams for years. As terrestrial areas within a watershed slowly recover, stream environments and biota can experience repeated and long-lasting challenges. In 2011, the Las Conchas wildfire burned 1/3 of the Valles Caldera National Preserve in northern New Mexico, USA. Seven y post-fire, streams located near the burn perimeter continue to experience varying levels of alteration (e.g., channel alteration with large diel temperature swings), whereas the terrestrial uplands have begun to recover. Extreme temperatures in stream systems may affect the aquatic community, including ectotherms such as caddisflies. These post-fire temperature ranges may increase an ectotherm’s breadth of thermal adaptation, but at metabolic costs that diminish organismal performance, such as growth, development, and fecundity. In this study we characterized in-situ effects of varied thermal regimes across preserve streams on the performance of the caddisfly Hydropsyche oslari Banks, 1905. We measured mass and critical thermal maximum (CTmax) in H. oslari larvae from preserve streams affected by wildfire (high temperature range) and in streams minimally affected by wildfire (low temperature range). We predicted that increased daily temperature maxima and reduced daily temperature minima (i.e., large diel temperature swings) would be associated with reduced H. oslari mass because of the limiting effects of suboptimal temperatures on growth. As predicted, in the weeks prior to their emergence as terrestrial adults, 5th-instar larvae within the high-temperature range stream had reduced mass (mean 3.3 ± SE 0.55 mg) relative to larvae from the low-temperature range stream (6.2 ± 0.69 mg). We also predicted that CTmax of H. oslari would reflect stream thermal history. Indeed, larvae H. oslari from the high-temperature range stream exhibited increased CTmax (35.4 ± 0.17°C) compared with larvae from the low-temperature range stream (34.4 ± 0.28°C). We demonstrated that the effects of wildfire on caddisflies can be long lasting, as evidenced by the reduced size at maturity and higher thermal tolerance in a caddisfly population 7 y post-fire.","PeriodicalId":48926,"journal":{"name":"Freshwater Science","volume":"41 1","pages":"62 - 76"},"PeriodicalIF":1.8,"publicationDate":"2021-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48585638","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
G. Lai, L. Ector, C. E. Wetzel, A. Lugliè, B. Padedda
Thermal springs provide natural laboratories to test the responses of biological communities to various stressors. To date, little is known about how water temperature and chemistry influence the microalgal assemblages in these ecosystems, especially in the circum-Mediterranean area. In this study, we assessed the environmental drivers of benthic diatom assemblages collected from different substrates in 8 thermo-mineral springs of Sardinia, Italy, with a focus on temperature and conductivity. A total of 205 diatom species (67 genera) were found, of which 12 (8 genera) were centric and 193 (59 genera) were pennate. Composition of diatom assemblages was associated with temperature, pH, conductivity, bicarbonates (HCO3−), and sulfates (SO42−). Multivariate analyses also confirmed differences in species composition, richness, diversity, and evenness of diatom assemblages from groups of springs distinguished by temperature and conductivity gradients. We found higher species richness, diversity, and evenness in hyperthermal (water temperature = 52.7−71.5°C) and medium-mineral springs (conductivity = 590−1193 µS/cm). Our results indicate that thermal springs are not always inhospitable environments for diatoms. Springs with high water temperatures hosted rich and diverse diatom assemblages, likely thanks to their ecotonal nature and a combination of multiple local factors.
{"title":"Environmental factors structuring diatom assemblages in thermo-mineral springs of Sardinia, Italy","authors":"G. Lai, L. Ector, C. E. Wetzel, A. Lugliè, B. Padedda","doi":"10.1086/718555","DOIUrl":"https://doi.org/10.1086/718555","url":null,"abstract":"Thermal springs provide natural laboratories to test the responses of biological communities to various stressors. To date, little is known about how water temperature and chemistry influence the microalgal assemblages in these ecosystems, especially in the circum-Mediterranean area. In this study, we assessed the environmental drivers of benthic diatom assemblages collected from different substrates in 8 thermo-mineral springs of Sardinia, Italy, with a focus on temperature and conductivity. A total of 205 diatom species (67 genera) were found, of which 12 (8 genera) were centric and 193 (59 genera) were pennate. Composition of diatom assemblages was associated with temperature, pH, conductivity, bicarbonates (HCO3−), and sulfates (SO42−). Multivariate analyses also confirmed differences in species composition, richness, diversity, and evenness of diatom assemblages from groups of springs distinguished by temperature and conductivity gradients. We found higher species richness, diversity, and evenness in hyperthermal (water temperature = 52.7−71.5°C) and medium-mineral springs (conductivity = 590−1193 µS/cm). Our results indicate that thermal springs are not always inhospitable environments for diatoms. Springs with high water temperatures hosted rich and diverse diatom assemblages, likely thanks to their ecotonal nature and a combination of multiple local factors.","PeriodicalId":48926,"journal":{"name":"Freshwater Science","volume":"41 1","pages":"45 - 61"},"PeriodicalIF":1.8,"publicationDate":"2021-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47255281","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Margot Sepp, T. Kõiv, P. Nõges, T. Nõges, Silvia E. Newell, M. J. McCarthy
Allochthonous supply of dissolved organic matter (DOM) and nutrients from the catchment have a substantial impact on the physical and chemical properties of lake water. Transport of DOM and nutrients is affected by different catchment characteristics, e.g., catchment area, soil and land cover, and population density. The aim of this study was to relate geological, hydrological, land-cover, and soil characteristics of 52 temperate catchments in Estonia to variability in DOM (measured as dissolved organic carbon [DOC]), total organic nitrogen (TON), and total phosphorus (TP) in lakes and to assess the relative importance of different land-cover and soil types as sources of these substances. DOC, TON, and TP were very diverse in the studied lakes. Strong positive correlation between DOC and TON indicated that these substances had similar concentration patterns and sources. Catchment soil cover was the best predictor of DOC, TON, and TP levels in lakes, explaining up to 43.8% of their variabilities. This observation can partly be explained by different soil organic carbon (SOC) content: soils with higher SOC were associated with higher lake DOC and TON, whereas soils with low SOC corresponded to lower DOC and TON. Similar to other temperate lakes, bogs and peat soils were a major source of DOM in our studied lakes. DOC, TON, and color were positively associated with percentages of peat soils in the catchment. On the other hand, TP increased with the proportion of urban areas in the catchments, indicating the importance of human impact on its concentration. Understanding the impact of different catchment characteristics on DOC, TON, and TP in temperate lakes is crucial for developing transport models used for predicting future levels of DOM and nutrients under changing climate and land use.
{"title":"Catchment soil characteristics predict organic carbon, nitrogen, and phosphorus levels in temperate lakes","authors":"Margot Sepp, T. Kõiv, P. Nõges, T. Nõges, Silvia E. Newell, M. J. McCarthy","doi":"10.1086/717954","DOIUrl":"https://doi.org/10.1086/717954","url":null,"abstract":"Allochthonous supply of dissolved organic matter (DOM) and nutrients from the catchment have a substantial impact on the physical and chemical properties of lake water. Transport of DOM and nutrients is affected by different catchment characteristics, e.g., catchment area, soil and land cover, and population density. The aim of this study was to relate geological, hydrological, land-cover, and soil characteristics of 52 temperate catchments in Estonia to variability in DOM (measured as dissolved organic carbon [DOC]), total organic nitrogen (TON), and total phosphorus (TP) in lakes and to assess the relative importance of different land-cover and soil types as sources of these substances. DOC, TON, and TP were very diverse in the studied lakes. Strong positive correlation between DOC and TON indicated that these substances had similar concentration patterns and sources. Catchment soil cover was the best predictor of DOC, TON, and TP levels in lakes, explaining up to 43.8% of their variabilities. This observation can partly be explained by different soil organic carbon (SOC) content: soils with higher SOC were associated with higher lake DOC and TON, whereas soils with low SOC corresponded to lower DOC and TON. Similar to other temperate lakes, bogs and peat soils were a major source of DOM in our studied lakes. DOC, TON, and color were positively associated with percentages of peat soils in the catchment. On the other hand, TP increased with the proportion of urban areas in the catchments, indicating the importance of human impact on its concentration. Understanding the impact of different catchment characteristics on DOC, TON, and TP in temperate lakes is crucial for developing transport models used for predicting future levels of DOM and nutrients under changing climate and land use.","PeriodicalId":48926,"journal":{"name":"Freshwater Science","volume":"41 1","pages":"1 - 17"},"PeriodicalIF":1.8,"publicationDate":"2021-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46431379","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Organisms that rely on detritus as their primary food source may face particularly strong nutritional constraints on growth and development, given the characteristically poor quality of detrital resources. In freshwater ecosystems, the low content of P in detritus often limits detritivore growth. Additionally, a growing body of evidence suggests the biochemical composition of algae, such as essential fatty acids, can limit aquatic detritivore growth. We investigated feeding preference and growth responses of common aquatic detritivores by performing paired feeding-preference and growth experiments on 4 species of larval caddisflies (Trichoptera) from the family Limnephilidae: Asynarchus nigriculus, Anabolia bimaculata, Limnephilus externus, and Ecclisomyia sp. We manipulated both the P content and epiphytic algal biomass of a common detrital food resource (decomposing sedge [Carex sp.]) by conditioning the detritus under 2 different light (ambient, shaded) and P (ambient [low], +P) regimes. We tested 3 hypotheses that describe feeding preferences and performance under different scenarios of P limitation, algal limitation, and co-limitation by P and algae. We observed evidence of preferential feeding behavior for each of the 4 taxa, with 2 species exhibiting preferences for conditioned detritus with high algal biomass and 2 for detritus from the +P treatments. We observed agreement between feeding preferences and performance (growth, growth efficiency, mortality) for only 2 taxa, with A. nigriculus exhibiting higher growth rates and growth efficiency on their preferred high-P detritus, and L. externus experiencing lower mortality when reared on their preferred high algal biomass detritus. These findings provide an initial step toward characterizing the feeding preferences and performance responses of aquatic detritivores to 2 potentially common nutritional constraints: detrital P and algal supply.
{"title":"Characterizing the role of phosphorus availability and periphytic algae in the food choice and performance of detritivorous caddisflies (Trichoptera:Limnephilidae)","authors":"Lee M. Demi, Donovan Hughes, B. W. Taylor","doi":"10.1086/717953","DOIUrl":"https://doi.org/10.1086/717953","url":null,"abstract":"Organisms that rely on detritus as their primary food source may face particularly strong nutritional constraints on growth and development, given the characteristically poor quality of detrital resources. In freshwater ecosystems, the low content of P in detritus often limits detritivore growth. Additionally, a growing body of evidence suggests the biochemical composition of algae, such as essential fatty acids, can limit aquatic detritivore growth. We investigated feeding preference and growth responses of common aquatic detritivores by performing paired feeding-preference and growth experiments on 4 species of larval caddisflies (Trichoptera) from the family Limnephilidae: Asynarchus nigriculus, Anabolia bimaculata, Limnephilus externus, and Ecclisomyia sp. We manipulated both the P content and epiphytic algal biomass of a common detrital food resource (decomposing sedge [Carex sp.]) by conditioning the detritus under 2 different light (ambient, shaded) and P (ambient [low], +P) regimes. We tested 3 hypotheses that describe feeding preferences and performance under different scenarios of P limitation, algal limitation, and co-limitation by P and algae. We observed evidence of preferential feeding behavior for each of the 4 taxa, with 2 species exhibiting preferences for conditioned detritus with high algal biomass and 2 for detritus from the +P treatments. We observed agreement between feeding preferences and performance (growth, growth efficiency, mortality) for only 2 taxa, with A. nigriculus exhibiting higher growth rates and growth efficiency on their preferred high-P detritus, and L. externus experiencing lower mortality when reared on their preferred high algal biomass detritus. These findings provide an initial step toward characterizing the feeding preferences and performance responses of aquatic detritivores to 2 potentially common nutritional constraints: detrital P and algal supply.","PeriodicalId":48926,"journal":{"name":"Freshwater Science","volume":"41 1","pages":"18 - 32"},"PeriodicalIF":1.8,"publicationDate":"2021-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45287396","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
K. Bouska, D. Larson, D. Drake, E. Lund, Alicia M. Carhart, Kyle R Bales
Macrophytes have recovered in rivers across the world, but long-term data and studies are lacking regarding community assembly and diversity changes coincident with macrophyte recovery. We investigated patterns of aquatic vegetation species composition and diversity in thousands of sites in the Upper Mississippi River, USA, spanning 21 y of monitoring and a period of vegetation recovery. We analyzed site-level compositional dissimilarity and environmental associations using non-metric multidimensional scaling, compared stability of lake-level assemblages over time with convex hulls, and assessed shared trends in assemblage dissimilarity at the pool scale using dynamic factor analysis. Site-level differences in aquatic vegetation assemblage structure were associated with water depth and substrate, and a gradient of species abundance and diversity was apparent. A common trend in assemblage dissimilarity over time and across contiguous floodplain lakes indicate that assemblage composition changed and diversity increased with considerable synchrony within the past 21 y. Shared trends across the 400-km study reach are indicative of 1 or more widespread, common drivers; however, neither hydrologic extremes nor turbidity explained vegetation assemblage patterns. Following several years of strong changes in composition and increased diversity, the vegetation assemblage displayed signs of increasing stability in some pools but not others. Further research is needed to identify drivers and mechanisms of aquatic vegetation assemblage expansion, assembly, and resilience, all of which will be applicable to the recovery of aquatic vegetation in floodplain systems worldwide.
{"title":"Aquatic vegetation dynamics in the Upper Mississippi River over 2 decades spanning vegetation recovery","authors":"K. Bouska, D. Larson, D. Drake, E. Lund, Alicia M. Carhart, Kyle R Bales","doi":"10.1086/717867","DOIUrl":"https://doi.org/10.1086/717867","url":null,"abstract":"Macrophytes have recovered in rivers across the world, but long-term data and studies are lacking regarding community assembly and diversity changes coincident with macrophyte recovery. We investigated patterns of aquatic vegetation species composition and diversity in thousands of sites in the Upper Mississippi River, USA, spanning 21 y of monitoring and a period of vegetation recovery. We analyzed site-level compositional dissimilarity and environmental associations using non-metric multidimensional scaling, compared stability of lake-level assemblages over time with convex hulls, and assessed shared trends in assemblage dissimilarity at the pool scale using dynamic factor analysis. Site-level differences in aquatic vegetation assemblage structure were associated with water depth and substrate, and a gradient of species abundance and diversity was apparent. A common trend in assemblage dissimilarity over time and across contiguous floodplain lakes indicate that assemblage composition changed and diversity increased with considerable synchrony within the past 21 y. Shared trends across the 400-km study reach are indicative of 1 or more widespread, common drivers; however, neither hydrologic extremes nor turbidity explained vegetation assemblage patterns. Following several years of strong changes in composition and increased diversity, the vegetation assemblage displayed signs of increasing stability in some pools but not others. Further research is needed to identify drivers and mechanisms of aquatic vegetation assemblage expansion, assembly, and resilience, all of which will be applicable to the recovery of aquatic vegetation in floodplain systems worldwide.","PeriodicalId":48926,"journal":{"name":"Freshwater Science","volume":"41 1","pages":"33 - 44"},"PeriodicalIF":1.8,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49215493","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
K. Tan, Chuancong Wang, Qiang Li, Dong Zhang, Ling Chu, Yunzhi Yan
Community assembly is generally affected by the spatial position of local patches. Examining metacommunity processes and structures in small streams with different river network positions (e.g., headwater streams in the periphery of river networks vs adventitious streams in relatively central positions) may help us better understand how spatial position influences metacommunity structuring. In this study, based on data collected from sampling 24 headwater and 15 adventitious stream sites in the Xin’an Basin, China, we examined whether and how fish metacommunity processes and structures differed between the 2 stream types. We used distanced-based redundancy analysis coupled with forward selection to assess the relative roles of environmental and spatial factors in metacommunity processes, and we applied the elements of metacommunity structure analysis, extended by using different ordinations, to identify metacommunity structures. We found that the 2 types of streams were similar in environmental heterogeneity, but fish assemblages in adventitious streams were more dissimilar to one another than were assemblages in headwater streams and had more riverine immigrants. The amount of among-stream variation in species composition was low in both stream types. In headwater streams, assemblage–environment relationships were stronger than assemblage–space relationships, but we found the opposite pattern in adventitious streams. Species turnover was strong in both headwater and adventitious streams. However, assemblages in headwater streams showed both nested and quasi-nested structures, whereas the assemblages in adventitious streams were more consistent with Clementsian structure. Our results suggest that different metacommunity processes may occur in small streams with distinct river network positions and that extended elements of metacommunity structure analysis can help identify the underlying mechanisms that produce metacommunity structure. The effect of spatial position within river networks on stream fish metacommunity structuring appears to be weak, but our analyses do imply that river immigrants can influence species composition in adventitious streams to some extent.
{"title":"Variation in processes structuring fish assemblages as inferred from metacommunity analyses: Differences between headwater and adventitious streams within a river network","authors":"K. Tan, Chuancong Wang, Qiang Li, Dong Zhang, Ling Chu, Yunzhi Yan","doi":"10.1086/717445","DOIUrl":"https://doi.org/10.1086/717445","url":null,"abstract":"Community assembly is generally affected by the spatial position of local patches. Examining metacommunity processes and structures in small streams with different river network positions (e.g., headwater streams in the periphery of river networks vs adventitious streams in relatively central positions) may help us better understand how spatial position influences metacommunity structuring. In this study, based on data collected from sampling 24 headwater and 15 adventitious stream sites in the Xin’an Basin, China, we examined whether and how fish metacommunity processes and structures differed between the 2 stream types. We used distanced-based redundancy analysis coupled with forward selection to assess the relative roles of environmental and spatial factors in metacommunity processes, and we applied the elements of metacommunity structure analysis, extended by using different ordinations, to identify metacommunity structures. We found that the 2 types of streams were similar in environmental heterogeneity, but fish assemblages in adventitious streams were more dissimilar to one another than were assemblages in headwater streams and had more riverine immigrants. The amount of among-stream variation in species composition was low in both stream types. In headwater streams, assemblage–environment relationships were stronger than assemblage–space relationships, but we found the opposite pattern in adventitious streams. Species turnover was strong in both headwater and adventitious streams. However, assemblages in headwater streams showed both nested and quasi-nested structures, whereas the assemblages in adventitious streams were more consistent with Clementsian structure. Our results suggest that different metacommunity processes may occur in small streams with distinct river network positions and that extended elements of metacommunity structure analysis can help identify the underlying mechanisms that produce metacommunity structure. The effect of spatial position within river networks on stream fish metacommunity structuring appears to be weak, but our analyses do imply that river immigrants can influence species composition in adventitious streams to some extent.","PeriodicalId":48926,"journal":{"name":"Freshwater Science","volume":"40 1","pages":"615 - 625"},"PeriodicalIF":1.8,"publicationDate":"2021-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44066260","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Susan Cragg, K. Cecala, Shawna M. Fix, J. Ennen, J. Davenport
Species interactions are important for determining the biological organization of natural communities. Presumably, as interacting organisms become more similar in resource niches, the magnitude of competition strength increases. However, the strength of interactions can be context dependent and mitigated by abiotic factors. In western North Carolina, headwater-stream salamanders and crayfish coexist across broad and fine spatial scales throughout their ranges. These dissimilar taxa occupy similar ecological niches within streams, yet there is limited understanding of the role that species interactions play in their local coexistence at fine spatial scales. We used both in-situ and ex-situ methods to evaluate the mechanisms promoting coexistence between stream salamanders (Desmognathus quadramaculatus [Holbrook, 1840] and Desmognathus marmoratus [Moore, 1899]) and Appalachian Brook Crayfish (Cambarus bartonii [Fabricius, 1798]). We conducted field surveys and documented factors potentially associated with refuge cohabitation between crayfish and salamanders within natural streams. We also used a stream mesocosm experiment to test if refuge density and competitor identity affected salamander and crayfish growth and behavior. In our in-situ approach, we found low interspecific cohabitation among desmognathan salamanders and C. bartonii with no detected effects of abiotic or biotic factors. Similarly, in our ex-situ experiment, we found that neither refuge density nor the presence of hetero- or conspecifics influenced the frequency of cohabitation and refuge use, growth, and mortality of D. quadramaculatus and C. bartonii. Although it is possible that local adaptation facilitates coexistence between our focal species, it is more likely that other abiotic (e.g., flow or temperature) and biotic factors (e.g., predators and other community members) in headwater streams besides the presence or absence of our focal taxa affect their distributions, or their interactions are size structured. These results support existing concepts that distantly related species are less likely to compete because of their morphological and phylogenetic dissimilarities, but future evaluations of interactions through time, space, and ontogeny would be useful to fully understand how these 2 taxa interact in headwater streams.
{"title":"Role of abiotic factors and habitat heterogeneity in the interactions between stream salamanders and crayfish in the southern Appalachians","authors":"Susan Cragg, K. Cecala, Shawna M. Fix, J. Ennen, J. Davenport","doi":"10.1086/717342","DOIUrl":"https://doi.org/10.1086/717342","url":null,"abstract":"Species interactions are important for determining the biological organization of natural communities. Presumably, as interacting organisms become more similar in resource niches, the magnitude of competition strength increases. However, the strength of interactions can be context dependent and mitigated by abiotic factors. In western North Carolina, headwater-stream salamanders and crayfish coexist across broad and fine spatial scales throughout their ranges. These dissimilar taxa occupy similar ecological niches within streams, yet there is limited understanding of the role that species interactions play in their local coexistence at fine spatial scales. We used both in-situ and ex-situ methods to evaluate the mechanisms promoting coexistence between stream salamanders (Desmognathus quadramaculatus [Holbrook, 1840] and Desmognathus marmoratus [Moore, 1899]) and Appalachian Brook Crayfish (Cambarus bartonii [Fabricius, 1798]). We conducted field surveys and documented factors potentially associated with refuge cohabitation between crayfish and salamanders within natural streams. We also used a stream mesocosm experiment to test if refuge density and competitor identity affected salamander and crayfish growth and behavior. In our in-situ approach, we found low interspecific cohabitation among desmognathan salamanders and C. bartonii with no detected effects of abiotic or biotic factors. Similarly, in our ex-situ experiment, we found that neither refuge density nor the presence of hetero- or conspecifics influenced the frequency of cohabitation and refuge use, growth, and mortality of D. quadramaculatus and C. bartonii. Although it is possible that local adaptation facilitates coexistence between our focal species, it is more likely that other abiotic (e.g., flow or temperature) and biotic factors (e.g., predators and other community members) in headwater streams besides the presence or absence of our focal taxa affect their distributions, or their interactions are size structured. These results support existing concepts that distantly related species are less likely to compete because of their morphological and phylogenetic dissimilarities, but future evaluations of interactions through time, space, and ontogeny would be useful to fully understand how these 2 taxa interact in headwater streams.","PeriodicalId":48926,"journal":{"name":"Freshwater Science","volume":"40 1","pages":"608 - 614"},"PeriodicalIF":1.8,"publicationDate":"2021-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46622810","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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