H. Guasch, S. Bernal, D. Bruno, B. C. Almroth, J. Cochero, Natàlia Corcoll, Delfina Cornejo, E. Gacia, A. Kroll, I. Lavoie, J. Ledesma, A. Lupon, H. Margenat, S. Morin, Enrique Navarro, M. Ribot, T. Riis, Mechthild Schmitt‐Jansen, A. Tlili, E. Martí
Plastics, especially microplastics (<5 mm in length), are anthropogenic polymer particles that have been detected in almost all environments. Microplastics are extremely persistent pollutants and act as long-lasting reactive surfaces for additives, organic matter, and toxic substances. Biofilms are microbial assemblages that act as a sink for particulate matter, including microplastics. They are ubiquitous in freshwater ecosystems and provide key services that promote biodiversity and help sustain ecosystem function. Here, we provide a conceptual framework to describe the transient storage of microplastics in fluvial biofilm and develop hypotheses to help explain how microplastics and biofilms interact in fluvial ecosystems. We identify lines of future research that need to be addressed to better manage microplastics and biofilms, including how the sorption and desorption of environmental contaminants in microplastics affect biofilms and how microbial exchange between microplastics and the biofilm matrix affects biofilm characteristics like antibiotic resistance, speciation, biodiversity, species composition, and function. We also address the uptake mechanisms of microplastics by consumers and their propagation through the food web.
{"title":"Interactions between microplastics and benthic biofilms in fluvial ecosystems: Knowledge gaps and future trends","authors":"H. Guasch, S. Bernal, D. Bruno, B. C. Almroth, J. Cochero, Natàlia Corcoll, Delfina Cornejo, E. Gacia, A. Kroll, I. Lavoie, J. Ledesma, A. Lupon, H. Margenat, S. Morin, Enrique Navarro, M. Ribot, T. Riis, Mechthild Schmitt‐Jansen, A. Tlili, E. Martí","doi":"10.1086/721472","DOIUrl":"https://doi.org/10.1086/721472","url":null,"abstract":"Plastics, especially microplastics (<5 mm in length), are anthropogenic polymer particles that have been detected in almost all environments. Microplastics are extremely persistent pollutants and act as long-lasting reactive surfaces for additives, organic matter, and toxic substances. Biofilms are microbial assemblages that act as a sink for particulate matter, including microplastics. They are ubiquitous in freshwater ecosystems and provide key services that promote biodiversity and help sustain ecosystem function. Here, we provide a conceptual framework to describe the transient storage of microplastics in fluvial biofilm and develop hypotheses to help explain how microplastics and biofilms interact in fluvial ecosystems. We identify lines of future research that need to be addressed to better manage microplastics and biofilms, including how the sorption and desorption of environmental contaminants in microplastics affect biofilms and how microbial exchange between microplastics and the biofilm matrix affects biofilm characteristics like antibiotic resistance, speciation, biodiversity, species composition, and function. We also address the uptake mechanisms of microplastics by consumers and their propagation through the food web.","PeriodicalId":48926,"journal":{"name":"Freshwater Science","volume":"41 1","pages":"442 - 458"},"PeriodicalIF":1.8,"publicationDate":"2022-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43505463","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}
R. C. P. Faquim, F. B. Teresa, P. P. Borges, K. B. Machado, J. Nabout
The organization of species metacommunities can be controlled by local factors, such as habitat quality, landscape factors, such as land use, and spatial factors, such as stream network distances. Species within a metacommunity have different traits that may be used to understand the determinants of community structure. This study aimed to understand how changes in environmental and spatial factors affected stream fish assemblages delineated based on their dispersal-related traits, such as preferential habitat use (i.e., benthic, nektobenthic, nektonic, marginal, and surface), preference for water velocity (i.e., fast, intermediate, and slow), and body size (i.e., small, medium, and large). We sampled 18 stream reaches in a dendritic network in the Upper Paraná River basin, located in the Brazilian Cerrado biome. We used variation partitioning techniques to test the relative effects of local environmental, landscape, and spatial variables on different species groups defined according to dispersal-related traits. Environmental and spatial variables weakly explained the variation in total assemblage taxonomic composition. However, based on different functional trait groups, we found that the environment had a strong relationship with assemblage composition of nektobenthic and small fish, whereas spatial variables were most strongly associated with marginal and surface fish. Large-scale spatial variables were associated with large fish and those that prefer slow water, whereas fine-scale variables were associated with small and surface-dwelling fish. These findings help improve understanding of how functional composition of stream fish assemblages may be affected by urban development, riparian conversion, and resulting changes in local environmental conditions.
{"title":"Differential responses of fish assemblages to environmental and spatial factors are mediated by dispersal-related traits in Neotropical streams","authors":"R. C. P. Faquim, F. B. Teresa, P. P. Borges, K. B. Machado, J. Nabout","doi":"10.1086/722356","DOIUrl":"https://doi.org/10.1086/722356","url":null,"abstract":"The organization of species metacommunities can be controlled by local factors, such as habitat quality, landscape factors, such as land use, and spatial factors, such as stream network distances. Species within a metacommunity have different traits that may be used to understand the determinants of community structure. This study aimed to understand how changes in environmental and spatial factors affected stream fish assemblages delineated based on their dispersal-related traits, such as preferential habitat use (i.e., benthic, nektobenthic, nektonic, marginal, and surface), preference for water velocity (i.e., fast, intermediate, and slow), and body size (i.e., small, medium, and large). We sampled 18 stream reaches in a dendritic network in the Upper Paraná River basin, located in the Brazilian Cerrado biome. We used variation partitioning techniques to test the relative effects of local environmental, landscape, and spatial variables on different species groups defined according to dispersal-related traits. Environmental and spatial variables weakly explained the variation in total assemblage taxonomic composition. However, based on different functional trait groups, we found that the environment had a strong relationship with assemblage composition of nektobenthic and small fish, whereas spatial variables were most strongly associated with marginal and surface fish. Large-scale spatial variables were associated with large fish and those that prefer slow water, whereas fine-scale variables were associated with small and surface-dwelling fish. These findings help improve understanding of how functional composition of stream fish assemblages may be affected by urban development, riparian conversion, and resulting changes in local environmental conditions.","PeriodicalId":48926,"journal":{"name":"Freshwater Science","volume":"41 1","pages":"549 - 563"},"PeriodicalIF":1.8,"publicationDate":"2022-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47122116","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}
E. Heiss, Victoria W. Zawacki, Audrey A. Williams, M. Reed, T. Maguire, Silvia E. Newell
Nitrification rates and ammonia-oxidizer functional gene abundance were measured in the water column of Lake Lacawac, Pennsylvania, USA, a freshwater lake on a nature sanctuary that allowed an investigation with minimal human impacts. Nitrification is a 2-step process consisting of ammonia oxidation followed by nitrite oxidation. Recent studies have shown that these 2 nitrification steps may be uncoupled and respond in different ways to environmental conditions. Additionally, the relative contribution of ammonia-oxidizing archea (AOA) vs ammonia-oxidizing bacteria (AOB) to nitrification rates varies widely across aquatic systems. To determine how nitrification rates are related to environmental parameters and the ammonia-oxidizing community in a nearly pristine environment, rates and gene abundance were measured over multiple seasons where in-situ environmental conditions varied. Rates of ammonia and nitrite oxidation were measured separately and summed to calculate total nitrification rates ranging from 1 to 568 nM/d. Ammonia oxidation rates generally outpaced nitrite oxidation rates, and rates of both ammonia and nitrite oxidation were higher at depth (10 m) compared with near-surface and mid water column. Ammonia oxidation, nitrite oxidation, and total nitrification rates were all strongly, positively correlated with in-situ [NH4+] (Kendall’s τ > 0.35, p < 0.02). AOB ammonia monooxygenase (amoA) gene copy numbers were generally greater than AOA amoA. However, AOB gene copy numbers were not correlated with any ammonia oxidation or total nitrification rates, whereas AOA abundance was positively correlated with both ammonia oxidation and total nitrification rates (Kendall’s τ > 0.41, p < 0.01). A Bayesian generalized additive model, which accounted for sampling month, indicated that total nitrification rates were best explained by AOA and [NH4+]. Thus, substrate concentration and AOA likely play key roles in regulating rates of nitrification in this small, nearly pristine freshwater lake. These reported relationships between rates of ammonia and nitrite oxidation (and, thus, total nitrification), in-situ environmental parameters, and the ammonia-oxidizer community in a protected environment establish a reference for evaluating the impact of a changing environment on mesotrophic lake water quality.
{"title":"Ammonia-oxidizing archaea and ammonium concentration as drivers of nitrification in a protected freshwater lake","authors":"E. Heiss, Victoria W. Zawacki, Audrey A. Williams, M. Reed, T. Maguire, Silvia E. Newell","doi":"10.1086/721921","DOIUrl":"https://doi.org/10.1086/721921","url":null,"abstract":"Nitrification rates and ammonia-oxidizer functional gene abundance were measured in the water column of Lake Lacawac, Pennsylvania, USA, a freshwater lake on a nature sanctuary that allowed an investigation with minimal human impacts. Nitrification is a 2-step process consisting of ammonia oxidation followed by nitrite oxidation. Recent studies have shown that these 2 nitrification steps may be uncoupled and respond in different ways to environmental conditions. Additionally, the relative contribution of ammonia-oxidizing archea (AOA) vs ammonia-oxidizing bacteria (AOB) to nitrification rates varies widely across aquatic systems. To determine how nitrification rates are related to environmental parameters and the ammonia-oxidizing community in a nearly pristine environment, rates and gene abundance were measured over multiple seasons where in-situ environmental conditions varied. Rates of ammonia and nitrite oxidation were measured separately and summed to calculate total nitrification rates ranging from 1 to 568 nM/d. Ammonia oxidation rates generally outpaced nitrite oxidation rates, and rates of both ammonia and nitrite oxidation were higher at depth (10 m) compared with near-surface and mid water column. Ammonia oxidation, nitrite oxidation, and total nitrification rates were all strongly, positively correlated with in-situ [NH4+] (Kendall’s τ > 0.35, p < 0.02). AOB ammonia monooxygenase (amoA) gene copy numbers were generally greater than AOA amoA. However, AOB gene copy numbers were not correlated with any ammonia oxidation or total nitrification rates, whereas AOA abundance was positively correlated with both ammonia oxidation and total nitrification rates (Kendall’s τ > 0.41, p < 0.01). A Bayesian generalized additive model, which accounted for sampling month, indicated that total nitrification rates were best explained by AOA and [NH4+]. Thus, substrate concentration and AOA likely play key roles in regulating rates of nitrification in this small, nearly pristine freshwater lake. These reported relationships between rates of ammonia and nitrite oxidation (and, thus, total nitrification), in-situ environmental parameters, and the ammonia-oxidizer community in a protected environment establish a reference for evaluating the impact of a changing environment on mesotrophic lake water quality.","PeriodicalId":48926,"journal":{"name":"Freshwater Science","volume":"41 1","pages":"564 - 576"},"PeriodicalIF":1.8,"publicationDate":"2022-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45745779","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}
The loading of chemical pollutants into stream systems can result in isolation of aquatic communities upstream of the discharge. Ecological theory suggests that isolation will result in species richness losses, but this potential indirect effect of stream pollution is not widely studied. Here, I present a study of fish assemblage structure in watersheds that have been longitudinally fragmented by abandoned mine drainage. A number of headwater streams in the Clarion River watershed of the upper Ohio River Basin, Pennsylvania, USA, have escaped any direct effects of abandoned mine drainage but have been isolated by severe pollution lower in the watershed. I evaluated the effects of watershed fragmentation on fish species richness, composition, and abundance by comparing the fish assemblages of 22 headwater streams embedded in watersheds receiving mine effluent with the assemblages of 34 reference streams with no apparent blockages to dispersal. I used a general linear model to evaluate the effect of isolation on species richness while accounting for stream size and water quality. I also used non-metric multidimensional scaling and permutational analysis of variance to evaluate differences in fish species composition between isolated and reference streams. Controlling for the effect of stream size, reference streams had a mean richness of 3.63 species (±0.27 SE), but isolated streams had a mean species richness of just 1.02 (±0.33), a 3.5× difference. Species occupying isolated stream systems were a nested subset of fish species in reference streams. Species composition also differed between isolated and reference streams, with higher relative abundance of Creek Chubs (Semotilus atromaculatus [Mitchill, 1818]) and lower relative abundances of Mottled Sculpin (Cottus bairdii Girard, 1850) and Brook Trout (Salvelinus fontinalis [Mitchill, 1814]) in isolated streams. These results illustrate an important indirect effect of water pollution in dendritic watersheds and provide evidence for the importance of connectivity in maintaining aquatic biodiversity.
{"title":"Chemical fragmentation of stream systems and fish species richness: The upstream effects of water pollution","authors":"A. Turner","doi":"10.1086/722102","DOIUrl":"https://doi.org/10.1086/722102","url":null,"abstract":"The loading of chemical pollutants into stream systems can result in isolation of aquatic communities upstream of the discharge. Ecological theory suggests that isolation will result in species richness losses, but this potential indirect effect of stream pollution is not widely studied. Here, I present a study of fish assemblage structure in watersheds that have been longitudinally fragmented by abandoned mine drainage. A number of headwater streams in the Clarion River watershed of the upper Ohio River Basin, Pennsylvania, USA, have escaped any direct effects of abandoned mine drainage but have been isolated by severe pollution lower in the watershed. I evaluated the effects of watershed fragmentation on fish species richness, composition, and abundance by comparing the fish assemblages of 22 headwater streams embedded in watersheds receiving mine effluent with the assemblages of 34 reference streams with no apparent blockages to dispersal. I used a general linear model to evaluate the effect of isolation on species richness while accounting for stream size and water quality. I also used non-metric multidimensional scaling and permutational analysis of variance to evaluate differences in fish species composition between isolated and reference streams. Controlling for the effect of stream size, reference streams had a mean richness of 3.63 species (±0.27 SE), but isolated streams had a mean species richness of just 1.02 (±0.33), a 3.5× difference. Species occupying isolated stream systems were a nested subset of fish species in reference streams. Species composition also differed between isolated and reference streams, with higher relative abundance of Creek Chubs (Semotilus atromaculatus [Mitchill, 1818]) and lower relative abundances of Mottled Sculpin (Cottus bairdii Girard, 1850) and Brook Trout (Salvelinus fontinalis [Mitchill, 1814]) in isolated streams. These results illustrate an important indirect effect of water pollution in dendritic watersheds and provide evidence for the importance of connectivity in maintaining aquatic biodiversity.","PeriodicalId":48926,"journal":{"name":"Freshwater Science","volume":"41 1","pages":"615 - 625"},"PeriodicalIF":1.8,"publicationDate":"2022-08-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41876953","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}
Autotrophic and heterotrophic microbes in stream biofilms dominate biogeochemical cycling and rely on nutrient and energy resources for growth and productivity. In the boreal forest, variation in these resources can originate from permafrost distribution and controls competition for nutrients between stream autotrophs and heterotrophs. We investigated which resources control nutrient uptake and metabolism in headwater stream biofilms of subarctic Alaska, USA, and how resource availability affects competition for inorganic nutrients. We hypothesized that the competitive outcome between autotrophs and heterotrophs for inorganic nutrients would be dependent on availability of organic C, or inorganic nutrients (N and P). To test our hypotheses, we measured resource limitation at the patch and reach scales along a permafrost gradient in interior Alaska. At the patch scale, nutrient diffusing substrata revealed that, secondary to light, N and P were colimiting to autotrophic growth, whereas C was primarily limiting to heterotrophic respiration. In the presence of labile C, heterotrophs exhibited a larger response to nutrient enrichment and outcompeted autotrophs for inorganic nutrients. At the reach scale, light availability had the largest influence on nutrient uptake, but inorganic nutrients were also important. The positive response to increased nutrient and C availability at the patch scale suggests that the predicted increase in exports into fluvial networks with permafrost degradation will alter biofilm structure and function. Ultimately, biofilm communities will shift to more heterotroph-dominated patches if heterotrophs outcompete autotrophs for inorganic nutrients. As permafrost thaws and nutrients and organic C mobilize into streams, nutrient uptake dynamics and competition within biofilms will be altered, affecting nutrient use and export.
{"title":"Resource limitation of autotrophs and heterotrophs in boreal forest headwater streams","authors":"Sophie Alden Weaver, Jeremy B. Jones","doi":"10.1086/722256","DOIUrl":"https://doi.org/10.1086/722256","url":null,"abstract":"Autotrophic and heterotrophic microbes in stream biofilms dominate biogeochemical cycling and rely on nutrient and energy resources for growth and productivity. In the boreal forest, variation in these resources can originate from permafrost distribution and controls competition for nutrients between stream autotrophs and heterotrophs. We investigated which resources control nutrient uptake and metabolism in headwater stream biofilms of subarctic Alaska, USA, and how resource availability affects competition for inorganic nutrients. We hypothesized that the competitive outcome between autotrophs and heterotrophs for inorganic nutrients would be dependent on availability of organic C, or inorganic nutrients (N and P). To test our hypotheses, we measured resource limitation at the patch and reach scales along a permafrost gradient in interior Alaska. At the patch scale, nutrient diffusing substrata revealed that, secondary to light, N and P were colimiting to autotrophic growth, whereas C was primarily limiting to heterotrophic respiration. In the presence of labile C, heterotrophs exhibited a larger response to nutrient enrichment and outcompeted autotrophs for inorganic nutrients. At the reach scale, light availability had the largest influence on nutrient uptake, but inorganic nutrients were also important. The positive response to increased nutrient and C availability at the patch scale suggests that the predicted increase in exports into fluvial networks with permafrost degradation will alter biofilm structure and function. Ultimately, biofilm communities will shift to more heterotroph-dominated patches if heterotrophs outcompete autotrophs for inorganic nutrients. As permafrost thaws and nutrients and organic C mobilize into streams, nutrient uptake dynamics and competition within biofilms will be altered, affecting nutrient use and export.","PeriodicalId":48926,"journal":{"name":"Freshwater Science","volume":"41 1","pages":"599 - 614"},"PeriodicalIF":1.8,"publicationDate":"2022-08-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42796116","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}
Human-mediated biological invasions can greatly reduce native species diversity. More than 138 nonnative fishes have been introduced to the United States. Many of these nonnative species can alter ecosystem dynamics and compete with native species. The planktivorous Silver Carp (Hypophthalmichthys molitrix Valenciennes in Cuvier and Valenciennes, 1844) is a nonnative species of concern that is currently expanding its range across the Greater Mississippi River Basin in the Midwestern United States. The objective of our study was to determine the degree of potential competition among invasive Silver Carp and the native planktivores, Gizzard Shad (Dorosoma cepedianum Lesueur, 1818) and Threadfin Shad (Dorosoma petenense Günther, 1867), in Kentucky Lake, a large reservoir located in western Kentucky and Tennessee. We used data derived from N and C isotopes to model isotopic niches, calculate quantitative metrics to describe variability within and among isotopic niches and trophic positions, and qualitatively assess seasonal shifts in trophic positions. Our results suggest that in the spring, older (≥1 y old) Silver Carp share resources with older and young-of-year (YOY; <1 y old) Gizzard Shad, whereas YOY Silver Carp only share resources with YOY Gizzard Shad. Additionally, our analyses showed that older Silver Carp and older Gizzard Shad share resources in the summer. In contrast, we found no overlap in resource use between YOY Threadfin Shad and YOY or older Silver Carp. Furthermore, we provide evidence of intraspecific ontogenetic shifts in isotopic niche area and overlap between invasive and native fishes (measured by sample-size corrected standard ellipse area). If resources become limiting, invasive Silver Carp may compete with multiple life stages of Gizzard Shad in Kentucky Lake and alter foodweb dynamics.
人类介导的生物入侵可以大大减少本地物种的多样性。超过138种非本地鱼类已被引入美国。这些非本地物种中的许多可以改变生态系统动态，并与本地物种竞争。浮游鲢鱼（Hyphonthamichthys molitrix Valenciennes in Cuvier and Valenciennens，1844）是一种令人担忧的非本地物种，目前正在美国中西部的大密西西比河流域扩大其范围。我们研究的目的是确定入侵鲢鱼与肯塔基湖（位于肯塔基州西部和田纳西州的一个大型水库）的本地浮游动物Gizzard Shad（Dorosoma cepedianum Lesueur，1818）和Threadfin Shad（多里斯玛petenense Günther，1867）之间的潜在竞争程度。我们使用来自N和C同位素的数据来建模同位素生态位，计算定量指标来描述同位素生态位和营养位置内部和之间的可变性，并定性评估营养位置的季节变化。我们的研究结果表明，在春季，年长（≥1岁）的鲢鱼与一年中的年长和年幼（YOY；<1岁）的Gizzard Shad共享资源，而YOY鲢鱼仅与YOY Gizzard Shad共享资源。此外，我们的分析表明，年长的鲢鱼和年长的Gizzard Shad在夏天共享资源。相比之下，我们发现YOY Threadfin Shad和YOY或更老的鲢鱼在资源使用方面没有重叠。此外，我们提供了同位素生态位区域的种内个体发生变化以及入侵鱼类和本地鱼类之间重叠的证据（通过样本大小校正的标准椭圆区域测量）。如果资源受到限制，入侵的鲢鱼可能会与肯塔基湖Gizzard Shad的多个生命阶段竞争，并改变食物网的动态。
{"title":"Isotopic niches of Silver Carp and two native planktivores in a large reservoir","authors":"D. Lebeda, Allison M. Lebeda, M. Flinn","doi":"10.1086/722054","DOIUrl":"https://doi.org/10.1086/722054","url":null,"abstract":"Human-mediated biological invasions can greatly reduce native species diversity. More than 138 nonnative fishes have been introduced to the United States. Many of these nonnative species can alter ecosystem dynamics and compete with native species. The planktivorous Silver Carp (Hypophthalmichthys molitrix Valenciennes in Cuvier and Valenciennes, 1844) is a nonnative species of concern that is currently expanding its range across the Greater Mississippi River Basin in the Midwestern United States. The objective of our study was to determine the degree of potential competition among invasive Silver Carp and the native planktivores, Gizzard Shad (Dorosoma cepedianum Lesueur, 1818) and Threadfin Shad (Dorosoma petenense Günther, 1867), in Kentucky Lake, a large reservoir located in western Kentucky and Tennessee. We used data derived from N and C isotopes to model isotopic niches, calculate quantitative metrics to describe variability within and among isotopic niches and trophic positions, and qualitatively assess seasonal shifts in trophic positions. Our results suggest that in the spring, older (≥1 y old) Silver Carp share resources with older and young-of-year (YOY; <1 y old) Gizzard Shad, whereas YOY Silver Carp only share resources with YOY Gizzard Shad. Additionally, our analyses showed that older Silver Carp and older Gizzard Shad share resources in the summer. In contrast, we found no overlap in resource use between YOY Threadfin Shad and YOY or older Silver Carp. Furthermore, we provide evidence of intraspecific ontogenetic shifts in isotopic niche area and overlap between invasive and native fishes (measured by sample-size corrected standard ellipse area). If resources become limiting, invasive Silver Carp may compete with multiple life stages of Gizzard Shad in Kentucky Lake and alter foodweb dynamics.","PeriodicalId":48926,"journal":{"name":"Freshwater Science","volume":"41 1","pages":"626 - 636"},"PeriodicalIF":1.8,"publicationDate":"2022-08-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43052966","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}
The predator-permanence hypothesis predicts that as hydroperiod increases in lentic ecosystems, biotic interactions—mainly predation—replace physical factors like drying as the main determinant of community structure and population dynamics. We propose that the same transition occurs over time in seasonally flooded ecosystems that are connected to permanent water bodies. To test for evidence of successional changes that are similar to spatial changes in the relative importance of drying and predation, we used a 12-y time series of snail density, predator density, and water depth at 4 sites arranged along a nutrient gradient in a subtropical, seasonally flooded wetland, the Florida Everglades, USA. The rate of change in snail population size was negatively correlated with their density at all 4 sites, suggesting that density-dependent factors such as resource limitation regulate snail dynamics. The strength of the relationship varied among sites such that when water depth changes were less important, snail population size was more important in predicting changes in snail population size. At the site that consistently had the greatest snail density, crayfish density negatively affected the rate of snail population change, suggesting that crayfish predation may limit snail population growth in areas with more or higher-quality resources that support larger snail populations. Tethering studies were also conducted, which revealed higher snail mortality in the wet season, primarily because crushing predators (e.g., molluscivorous fishes) were more common at that time and added to the chronic mortality by entry-based predators (e.g., crayfish, which access snails through their aperture). In summary, 3 of the sites resembled temporary or permanent fishless ponds where snail populations were primarily structured by abiotic factors, intraspecific competition, and invertebrate predators (e.g., crayfish) during the wet season, whereas 1 site showed evidence that snail populations were also influenced by molluscivorous fish. This temporal change in importance of water permanence factors to fish that affected population dynamics supports the spatial pattern proposed by the predator-permanence hypothesis.
{"title":"Predator-permanence hypothesis in time: Community dynamics in a seasonally flooded wetland","authors":"Clifton B Ruehl, M. Pintar, J. Trexler","doi":"10.1086/721960","DOIUrl":"https://doi.org/10.1086/721960","url":null,"abstract":"The predator-permanence hypothesis predicts that as hydroperiod increases in lentic ecosystems, biotic interactions—mainly predation—replace physical factors like drying as the main determinant of community structure and population dynamics. We propose that the same transition occurs over time in seasonally flooded ecosystems that are connected to permanent water bodies. To test for evidence of successional changes that are similar to spatial changes in the relative importance of drying and predation, we used a 12-y time series of snail density, predator density, and water depth at 4 sites arranged along a nutrient gradient in a subtropical, seasonally flooded wetland, the Florida Everglades, USA. The rate of change in snail population size was negatively correlated with their density at all 4 sites, suggesting that density-dependent factors such as resource limitation regulate snail dynamics. The strength of the relationship varied among sites such that when water depth changes were less important, snail population size was more important in predicting changes in snail population size. At the site that consistently had the greatest snail density, crayfish density negatively affected the rate of snail population change, suggesting that crayfish predation may limit snail population growth in areas with more or higher-quality resources that support larger snail populations. Tethering studies were also conducted, which revealed higher snail mortality in the wet season, primarily because crushing predators (e.g., molluscivorous fishes) were more common at that time and added to the chronic mortality by entry-based predators (e.g., crayfish, which access snails through their aperture). In summary, 3 of the sites resembled temporary or permanent fishless ponds where snail populations were primarily structured by abiotic factors, intraspecific competition, and invertebrate predators (e.g., crayfish) during the wet season, whereas 1 site showed evidence that snail populations were also influenced by molluscivorous fish. This temporal change in importance of water permanence factors to fish that affected population dynamics supports the spatial pattern proposed by the predator-permanence hypothesis.","PeriodicalId":48926,"journal":{"name":"Freshwater Science","volume":"41 1","pages":"637 - 649"},"PeriodicalIF":1.8,"publicationDate":"2022-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47874643","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}
Erika Díaz-Pascacio, M. M. Castillo, Na’Taki Osborne Jelks
As the practice of stream restoration continues expanding globally, the importance of including social factors and communities within the restoration or revitalization process also increases. Engineers and environmental scientists have acknowledged the crucial role of actively involving such communities, but community involvement poses challenges because there is little guidance on managing social processes and balancing different interests. Although many restoration efforts appear to be addressing the needs of crucial ecological habitats, there have been concerning disparities identified associated to race, ethnicity, and income. Through examining 2 case studies, we attempt to identify historical trends and to describe inequities, environmental burdens, and urgent needs of oppressed communities. This validation process also led us to explore systemic constraints that can perpetuate injustices. We suggest that an equity and environmental justice perspective can provide both context and an opportunity to recognize and address basic needs of communities. The ultimate goal of stream restoration should be to achieve solutions that provide true justice; therefore, considering power relations and finding causes rather than symptoms of inequities are both important to achieving more sustainable and equitable stream restoration outcomes.
{"title":"Including equity in urban stream restoration: From historical wrongs to new paradigms","authors":"Erika Díaz-Pascacio, M. M. Castillo, Na’Taki Osborne Jelks","doi":"10.1086/721651","DOIUrl":"https://doi.org/10.1086/721651","url":null,"abstract":"As the practice of stream restoration continues expanding globally, the importance of including social factors and communities within the restoration or revitalization process also increases. Engineers and environmental scientists have acknowledged the crucial role of actively involving such communities, but community involvement poses challenges because there is little guidance on managing social processes and balancing different interests. Although many restoration efforts appear to be addressing the needs of crucial ecological habitats, there have been concerning disparities identified associated to race, ethnicity, and income. Through examining 2 case studies, we attempt to identify historical trends and to describe inequities, environmental burdens, and urgent needs of oppressed communities. This validation process also led us to explore systemic constraints that can perpetuate injustices. We suggest that an equity and environmental justice perspective can provide both context and an opportunity to recognize and address basic needs of communities. The ultimate goal of stream restoration should be to achieve solutions that provide true justice; therefore, considering power relations and finding causes rather than symptoms of inequities are both important to achieving more sustainable and equitable stream restoration outcomes.","PeriodicalId":48926,"journal":{"name":"Freshwater Science","volume":"41 1","pages":"539 - 547"},"PeriodicalIF":1.8,"publicationDate":"2022-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41494752","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}
B. Murphy, Kathryn L. Russell, Charles C. Stillwell, R. Hawley, M. Scoggins, K. Hopkins, M. Burns, Kristine Taniguchi-Quan, K. Macneale, Robert Smith
Restoring the health of urban streams has many of the characteristics of a wicked problem. Addressing a wicked problem requires managers, academics, practitioners, and community members to make negotiated tradeoffs and compromises to satisfy the values and perspectives of diverse stakeholders involved in setting restoration project goals and objectives. We conducted a gap analysis on 11 urban stream restoration projects to identify disconnections, underperformance issues, and missing processes in the project structures used to develop restoration project goals and objectives. We examined the gap analysis results to investigate whether managers appropriately identified problem statements and met stated objectives. Projects that aimed to restore overall stream health commonly fell short for various reasons, including limited stakeholder and community input and buy-in, revealing potential limitations in the breadth of objectives, values, and stakeholder perspectives and knowledge types. Projects that emphasized integrating community values and diverse knowledge types tended to meet the expected outcomes of restoring stream processes through incremental solutions. Managers implementing more holistic solutions and values-driven approaches are more likely to consider diverse viewpoints from a variety of community local institutions. Based on these and other results, we propose a conceptual framework that integrates diverse perspectives and knowledge to enhance social and ecological outcomes of urban stream restoration. The framework also emphasizes the importance of setting objectives that support incremental solutions to foster more realistic expectations amongst stakeholders.
{"title":"Closing the gap on wicked urban stream restoration problems: A framework to integrate science and community values","authors":"B. Murphy, Kathryn L. Russell, Charles C. Stillwell, R. Hawley, M. Scoggins, K. Hopkins, M. Burns, Kristine Taniguchi-Quan, K. Macneale, Robert Smith","doi":"10.1086/721134","DOIUrl":"https://doi.org/10.1086/721134","url":null,"abstract":"Restoring the health of urban streams has many of the characteristics of a wicked problem. Addressing a wicked problem requires managers, academics, practitioners, and community members to make negotiated tradeoffs and compromises to satisfy the values and perspectives of diverse stakeholders involved in setting restoration project goals and objectives. We conducted a gap analysis on 11 urban stream restoration projects to identify disconnections, underperformance issues, and missing processes in the project structures used to develop restoration project goals and objectives. We examined the gap analysis results to investigate whether managers appropriately identified problem statements and met stated objectives. Projects that aimed to restore overall stream health commonly fell short for various reasons, including limited stakeholder and community input and buy-in, revealing potential limitations in the breadth of objectives, values, and stakeholder perspectives and knowledge types. Projects that emphasized integrating community values and diverse knowledge types tended to meet the expected outcomes of restoring stream processes through incremental solutions. Managers implementing more holistic solutions and values-driven approaches are more likely to consider diverse viewpoints from a variety of community local institutions. Based on these and other results, we propose a conceptual framework that integrates diverse perspectives and knowledge to enhance social and ecological outcomes of urban stream restoration. The framework also emphasizes the importance of setting objectives that support incremental solutions to foster more realistic expectations amongst stakeholders.","PeriodicalId":48926,"journal":{"name":"Freshwater Science","volume":"41 1","pages":"521 - 531"},"PeriodicalIF":1.8,"publicationDate":"2022-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46253743","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}
S. E. Orr, J. Cochran, I. Wallace, Rachel W. Gray, Gretta E. Overmyer, D. Buchwalter
Freshwater salinization is a global ecological concern because of the alarming biodiversity declines associated with increases in major ion concentrations. Loss of mayfly diversity appears to be a common ecological response to anthropogenic salinization worldwide. Remarkably few regulatory standards exist to protect aquatic life from major ions, and antiquated approaches for setting such standards rely on traditional laboratory toxicity tests, which do not address sensitivities of mayflies at different larval stages. The lab-reared mayfly Neocloeon triangulifer (McDunnough, 1931) has emerged as one of the very few useful aquatic insect models for studying the effects of environmental stressors, including salinity, in the laboratory. Here, we asked if different larval life stages are differentially sensitivity to ion concentrations by conducting traditional 96-h toxicity tests with NaCl, CaCl2, and Ca/MgSO4. We used a general linear model to determine if survivorship differed among larval stages as well as ion type and concentration. We also calculated median lethal concentrations (LC50) for each larval stage. Larval sensitivity to NaCl decreased slightly with age (2–6, 9–13, and 17–21 d, with LC50 values of 401, 441, and 570 mg/L, respectively, when expressed as Na concentrations). Similarly, larval sensitivity to Ca/MgSO4 differed slightly among age groups (LC50 = 748, 1503, and 1439 mg/L, respectively, when expressed as SO4 concentrations). Reliable confidence intervals on LC50 values for CaCl2 could not be calculated because of high survivorship. However, our general linear model revealed that age played a moderate role in survival (p = 0.0065) across all salts of interest. To assess the potential changes in ion flux between larval stages, we used radiotracers (22Na, 35SO4, or 45Ca) in 18- and 25-d-old larvae and found no strong differences in ion uptake rates. We also qualitatively examined morphological differences between larval life stages, including the appearance of gills and number of ionocytes. Our results indicate that younger N. triangulifer larvae may be more sensitive to major ions than mature larvae. These results should be considered when experimentally using larger, late-stage N. triangulifer larvae to study the physiological effects and acute toxicity of salinity.
{"title":"Weak differences in sensitivity to major ions by different larval stages of the mayfly Neocloeon triangulifer","authors":"S. E. Orr, J. Cochran, I. Wallace, Rachel W. Gray, Gretta E. Overmyer, D. Buchwalter","doi":"10.1086/719359","DOIUrl":"https://doi.org/10.1086/719359","url":null,"abstract":"Freshwater salinization is a global ecological concern because of the alarming biodiversity declines associated with increases in major ion concentrations. Loss of mayfly diversity appears to be a common ecological response to anthropogenic salinization worldwide. Remarkably few regulatory standards exist to protect aquatic life from major ions, and antiquated approaches for setting such standards rely on traditional laboratory toxicity tests, which do not address sensitivities of mayflies at different larval stages. The lab-reared mayfly Neocloeon triangulifer (McDunnough, 1931) has emerged as one of the very few useful aquatic insect models for studying the effects of environmental stressors, including salinity, in the laboratory. Here, we asked if different larval life stages are differentially sensitivity to ion concentrations by conducting traditional 96-h toxicity tests with NaCl, CaCl2, and Ca/MgSO4. We used a general linear model to determine if survivorship differed among larval stages as well as ion type and concentration. We also calculated median lethal concentrations (LC50) for each larval stage. Larval sensitivity to NaCl decreased slightly with age (2–6, 9–13, and 17–21 d, with LC50 values of 401, 441, and 570 mg/L, respectively, when expressed as Na concentrations). Similarly, larval sensitivity to Ca/MgSO4 differed slightly among age groups (LC50 = 748, 1503, and 1439 mg/L, respectively, when expressed as SO4 concentrations). Reliable confidence intervals on LC50 values for CaCl2 could not be calculated because of high survivorship. However, our general linear model revealed that age played a moderate role in survival (p = 0.0065) across all salts of interest. To assess the potential changes in ion flux between larval stages, we used radiotracers (22Na, 35SO4, or 45Ca) in 18- and 25-d-old larvae and found no strong differences in ion uptake rates. We also qualitatively examined morphological differences between larval life stages, including the appearance of gills and number of ionocytes. Our results indicate that younger N. triangulifer larvae may be more sensitive to major ions than mature larvae. These results should be considered when experimentally using larger, late-stage N. triangulifer larvae to study the physiological effects and acute toxicity of salinity.","PeriodicalId":48926,"journal":{"name":"Freshwater Science","volume":"41 1","pages":"215 - 225"},"PeriodicalIF":1.8,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"60725914","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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