Abstract Pesticides play a critical role in maximizing yields of economically important crops and minimizing the human health threats of disease-carrying pests, but they often have collateral effects on nontarget species. We used a mesocosm study to address how the most commonly used insecticide in the USA, malathion, applied at low, ecologically relevant concentrations (20 and 110 µg/L) affects species interactions in aquatic communities. Unlike many community ecotoxicology studies, our study assessed how malathion affects both consumptive and nonconsumptive effects of predators. We also considered how the vertical distribution of predator cues and malathion (caused by potential stratification) affects species interactions. We found no evidence for vertical stratification of malathion, a result suggesting that exposure to the pesticide was uniform throughout the water column. Malathion was lethal to some primary consumers (cladocerans) at both concentrations and to top predators (dragonflies) at the highest concentration (110 µg/L). These lethal effects initiated density-mediated indirect effects in both cases. Malathion also may have decreased dragonfly foraging efficiency, resulting in increased tadpole survival (trait-mediated indirect effect), which decreased the resources used by tadpoles (periphyton). Collectively, our results show that malathion alters species interactions. However, we suggest that the degree to which pesticides affect aquatic communities will depend strongly on the species composition of communities. Therefore, the community-level consequences of pesticide exposure are likely to vary across the ecological landscape.
{"title":"Altering aquatic food webs with a global insecticide: arthropod–amphibian links in mesocosms that simulate pond communities","authors":"Rickey D. Cothran, Forrest Radarian, R. Relyea","doi":"10.1899/11-011.1","DOIUrl":"https://doi.org/10.1899/11-011.1","url":null,"abstract":"Abstract Pesticides play a critical role in maximizing yields of economically important crops and minimizing the human health threats of disease-carrying pests, but they often have collateral effects on nontarget species. We used a mesocosm study to address how the most commonly used insecticide in the USA, malathion, applied at low, ecologically relevant concentrations (20 and 110 µg/L) affects species interactions in aquatic communities. Unlike many community ecotoxicology studies, our study assessed how malathion affects both consumptive and nonconsumptive effects of predators. We also considered how the vertical distribution of predator cues and malathion (caused by potential stratification) affects species interactions. We found no evidence for vertical stratification of malathion, a result suggesting that exposure to the pesticide was uniform throughout the water column. Malathion was lethal to some primary consumers (cladocerans) at both concentrations and to top predators (dragonflies) at the highest concentration (110 µg/L). These lethal effects initiated density-mediated indirect effects in both cases. Malathion also may have decreased dragonfly foraging efficiency, resulting in increased tadpole survival (trait-mediated indirect effect), which decreased the resources used by tadpoles (periphyton). Collectively, our results show that malathion alters species interactions. However, we suggest that the degree to which pesticides affect aquatic communities will depend strongly on the species composition of communities. Therefore, the community-level consequences of pesticide exposure are likely to vary across the ecological landscape.","PeriodicalId":49987,"journal":{"name":"Journal of the North American Benthological Society","volume":"30 1","pages":"893 - 912"},"PeriodicalIF":0.0,"publicationDate":"2011-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87583902","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 Detrital inputs into ecosystems vary in quantity and quality (e.g., plant litter vs carrion). Variability in detrital quantity and quality potentially affects consumer biomass and rates of organic matter (OM) breakdown. We used cave streams to test 2 linked hypotheses regarding the influence of total detrital inputs on consumer biomass and the breakdown of high-quality carrion detritus. First, we hypothesized that cave systems with higher total OM availability would support a higher biomass of consumers. Second, we predicted that higher consumer biomass would cause faster carrion breakdown rates. To test these hypotheses, we quantified macroinvertebrate biomass and breakdown rates (k, d−1) of carrion (mouse carcasses, Mus musculus) in 4 cave streams in northeastern Alabama and southeastern Tennessee (USA) that varied in total OM storage. We estimated carrion breakdown rates in coarse- and fine-mesh packs (10-mm and 500-µm mesh size) to isolate the influence of scavenging by crayfish. Macroinvertebrate biomass (excluding crayfish) in carrion packs was positively correlated with OM storage, but neither macroinvertebrate biomass (excluding crayfish) nor OM storage were strong predictors of carrion breakdown rates. Crayfish biomass was not correlated with total OM storage but was positively correlated with coarse-mesh breakdown rates. Our study illustrates the influence of community structure and consumer biomass on detrital breakdown rates in cave ecosystems. However, determining how detrital inputs structure cave communities will require further study.
输入生态系统的碎屑在数量和质量上各不相同(例如，植物凋落物与腐肉)。碎屑数量和质量的变化可能影响消费者生物量和有机物分解速率。我们使用洞穴溪流来测试关于总碎屑输入对消费者生物量和高质量腐肉碎屑分解的影响的两个关联假设。首先，我们假设总有机质利用率较高的洞穴系统将支持更高的消费者生物量。其次，我们预测更高的消费生物量将导致更快的腐肉分解率。为了验证这些假设，我们在美国阿拉巴马州东北部和田纳西州东南部的4个洞穴溪流中量化了大型无脊椎动物的生物量和腐肉(老鼠尸体，小家鼠)的分解率(k, d - 1)。我们估计了粗网和细网包装(10毫米和500微米)中的腐肉分解率，以分离小龙虾清除的影响。大型无脊椎动物生物量(不包括小龙虾)与腐肉储量呈正相关，但大型无脊椎动物生物量(不包括小龙虾)和OM储量都不是腐肉分解率的强预测因子。小龙虾生物量与总OM储量不相关，但与粗网击穿率正相关。我们的研究说明了群落结构和消费者生物量对洞穴生态系统中碎屑分解率的影响。然而，确定碎屑输入如何构成洞穴群落将需要进一步研究。
{"title":"Relating carrion breakdown rates to ambient resource level and community structure in four cave stream ecosystems","authors":"Brock M. Huntsman, M. Venarsky, J. Benstead","doi":"10.1899/10-116.1","DOIUrl":"https://doi.org/10.1899/10-116.1","url":null,"abstract":"Abstract Detrital inputs into ecosystems vary in quantity and quality (e.g., plant litter vs carrion). Variability in detrital quantity and quality potentially affects consumer biomass and rates of organic matter (OM) breakdown. We used cave streams to test 2 linked hypotheses regarding the influence of total detrital inputs on consumer biomass and the breakdown of high-quality carrion detritus. First, we hypothesized that cave systems with higher total OM availability would support a higher biomass of consumers. Second, we predicted that higher consumer biomass would cause faster carrion breakdown rates. To test these hypotheses, we quantified macroinvertebrate biomass and breakdown rates (k, d−1) of carrion (mouse carcasses, Mus musculus) in 4 cave streams in northeastern Alabama and southeastern Tennessee (USA) that varied in total OM storage. We estimated carrion breakdown rates in coarse- and fine-mesh packs (10-mm and 500-µm mesh size) to isolate the influence of scavenging by crayfish. Macroinvertebrate biomass (excluding crayfish) in carrion packs was positively correlated with OM storage, but neither macroinvertebrate biomass (excluding crayfish) nor OM storage were strong predictors of carrion breakdown rates. Crayfish biomass was not correlated with total OM storage but was positively correlated with coarse-mesh breakdown rates. Our study illustrates the influence of community structure and consumer biomass on detrital breakdown rates in cave ecosystems. However, determining how detrital inputs structure cave communities will require further study.","PeriodicalId":49987,"journal":{"name":"Journal of the North American Benthological Society","volume":"17 1","pages":"882 - 892"},"PeriodicalIF":0.0,"publicationDate":"2011-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73703223","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}
L. Filipová, David A Lieb, F. Grandjean, A. Petrusek
Abstract The North American spiny-cheek crayfish, Orconectes limosus (Rafinesque, 1817), a widespread invader in Europe, seems to have been introduced there successfully only once. According to available literature, 90 individuals of unclear origin were released in Poland in 1890. Despite this apparent bottleneck, the species has successfully colonized various aquatic habitats and has displaced native crayfish species in many places. To test whether different European populations were likely to have come from a single source and to identify their possible origin, we analyzed the diversity of the mitochondrial gene for cytochrome c oxidase subunit I (COI) of O. limosus individuals from Europe and from its original range in North America, including the presumed source region of European populations, the Delaware River watershed (eastern USA). Two haplotypes were found in European populations. One haplotype was widespread; the other was present in a single population. In contrast, 18 haplotypes were detected in North America. This result supports the hypothesis of a single overseas introduction of O. limosus and suggests that the high invasion success of this species was not limited by an introduction bottleneck. Two divergent clades were detected in North American O. limosus populations. One, which includes the dominant haplotype in Europe, was found in a large part of the species' present range. The 2nd (diverging by >1%) was mostly restricted to a limited area in southeastern Pennsylvania. Orconectes limosus populations in the northern part of the species' North American range, at least some of which are nonindigenous themselves, may share the source area with European O. limosus. The endangered status of O. limosus populations in southeastern Pennsylvania and northeastern Maryland, where much of the species' genetic diversity resides, should be considered in conservation management.
{"title":"Haplotype variation in the spiny-cheek crayfish Orconectes limosus: colonization of Europe and genetic diversity of native stocks","authors":"L. Filipová, David A Lieb, F. Grandjean, A. Petrusek","doi":"10.1899/10-130.1","DOIUrl":"https://doi.org/10.1899/10-130.1","url":null,"abstract":"Abstract The North American spiny-cheek crayfish, Orconectes limosus (Rafinesque, 1817), a widespread invader in Europe, seems to have been introduced there successfully only once. According to available literature, 90 individuals of unclear origin were released in Poland in 1890. Despite this apparent bottleneck, the species has successfully colonized various aquatic habitats and has displaced native crayfish species in many places. To test whether different European populations were likely to have come from a single source and to identify their possible origin, we analyzed the diversity of the mitochondrial gene for cytochrome c oxidase subunit I (COI) of O. limosus individuals from Europe and from its original range in North America, including the presumed source region of European populations, the Delaware River watershed (eastern USA). Two haplotypes were found in European populations. One haplotype was widespread; the other was present in a single population. In contrast, 18 haplotypes were detected in North America. This result supports the hypothesis of a single overseas introduction of O. limosus and suggests that the high invasion success of this species was not limited by an introduction bottleneck. Two divergent clades were detected in North American O. limosus populations. One, which includes the dominant haplotype in Europe, was found in a large part of the species' present range. The 2nd (diverging by >1%) was mostly restricted to a limited area in southeastern Pennsylvania. Orconectes limosus populations in the northern part of the species' North American range, at least some of which are nonindigenous themselves, may share the source area with European O. limosus. The endangered status of O. limosus populations in southeastern Pennsylvania and northeastern Maryland, where much of the species' genetic diversity resides, should be considered in conservation management.","PeriodicalId":49987,"journal":{"name":"Journal of the North American Benthological Society","volume":"45 1","pages":"871 - 881"},"PeriodicalIF":0.0,"publicationDate":"2011-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82054578","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}
T. Cuffney, R. Kashuba, S. Qian, I. Alameddine, YoonKyung Cha, Boknam Lee, J. Coles, G. McMahon
Abstract Multilevel hierarchical regression was used to examine regional patterns in the responses of benthic macroinvertebrates and algae to urbanization across 9 metropolitan areas of the conterminous USA. Linear regressions established that responses (intercepts and slopes) to urbanization of invertebrates and algae varied among metropolitan areas. Multilevel hierarchical regression models were able to explain these differences on the basis of region-scale predictors. Regional differences in the type of land cover (agriculture or forest) being converted to urban and climatic factors (precipitation and air temperature) accounted for the differences in the response of macroinvertebrates to urbanization based on ordination scores, total richness, Ephemeroptera, Plecoptera, Trichoptera richness, and average tolerance. Regional differences in climate and antecedent agriculture also accounted for differences in the responses of salt-tolerant diatoms, but differences in the responses of other diatom metrics (% eutraphenic, % sensitive, and % silt tolerant) were best explained by regional differences in soils (mean % clay soils). The effects of urbanization were most readily detected in regions where forest lands were being converted to urban land because agricultural development significantly degraded assemblages before urbanization and made detection of urban effects difficult. The effects of climatic factors (temperature, precipitation) on background conditions (biogeographic differences) and rates of response to urbanization were most apparent after accounting for the effects of agricultural development. The effects of climate and land cover on responses to urbanization provide strong evidence that monitoring, mitigation, and restoration efforts must be tailored for specific regions and that attainment goals (background conditions) may not be possible in regions with high levels of prior disturbance (e.g., agricultural development).
{"title":"Multilevel regression models describing regional patterns of invertebrate and algal responses to urbanization across the USA","authors":"T. Cuffney, R. Kashuba, S. Qian, I. Alameddine, YoonKyung Cha, Boknam Lee, J. Coles, G. McMahon","doi":"10.1899/10-140.1","DOIUrl":"https://doi.org/10.1899/10-140.1","url":null,"abstract":"Abstract Multilevel hierarchical regression was used to examine regional patterns in the responses of benthic macroinvertebrates and algae to urbanization across 9 metropolitan areas of the conterminous USA. Linear regressions established that responses (intercepts and slopes) to urbanization of invertebrates and algae varied among metropolitan areas. Multilevel hierarchical regression models were able to explain these differences on the basis of region-scale predictors. Regional differences in the type of land cover (agriculture or forest) being converted to urban and climatic factors (precipitation and air temperature) accounted for the differences in the response of macroinvertebrates to urbanization based on ordination scores, total richness, Ephemeroptera, Plecoptera, Trichoptera richness, and average tolerance. Regional differences in climate and antecedent agriculture also accounted for differences in the responses of salt-tolerant diatoms, but differences in the responses of other diatom metrics (% eutraphenic, % sensitive, and % silt tolerant) were best explained by regional differences in soils (mean % clay soils). The effects of urbanization were most readily detected in regions where forest lands were being converted to urban land because agricultural development significantly degraded assemblages before urbanization and made detection of urban effects difficult. The effects of climatic factors (temperature, precipitation) on background conditions (biogeographic differences) and rates of response to urbanization were most apparent after accounting for the effects of agricultural development. The effects of climate and land cover on responses to urbanization provide strong evidence that monitoring, mitigation, and restoration efforts must be tailored for specific regions and that attainment goals (background conditions) may not be possible in regions with high levels of prior disturbance (e.g., agricultural development).","PeriodicalId":49987,"journal":{"name":"Journal of the North American Benthological Society","volume":"17 1","pages":"797 - 819"},"PeriodicalIF":0.0,"publicationDate":"2011-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82028369","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 Benthic invertebrates have important ecosystem engineering functions (bioturbation and biodeposition) in freshwater and marine benthic systems. Bioturbation and biodeposition affect the metabolism of the water–sediment interface through modification of water–sediment fluxes or organic-matter enrichment of sediments by biodeposits. The functional significance of these processes depends strongly on the type of invertebrate activities (the functional traits of the invertebrates) and on the modulation of this activity by environmental conditions. The aim of my article is to propose a common framework for the role of bioturbation/biodeposition in benthic habitats of both marine and freshwater environments. In these ecosystems, hydrological exchanges between the water and sediments (interstitial flow rates) control the microbial activity inside sediments. The ability of ecosystem engineers to influence benthic microbial processes differs strongly between diffusion-dominated (low interstitial flow rates) and advection-dominated (high interstitial flow rates) habitats. Bioturbation/biodeposition may play a role in diffusion-dominated habitats where invertebrates can significantly modify water and particle fluxes at the water–sediment interface, whereas a slight influence of ecosystem engineers is expected in advection-dominated habitats where fluxes are predominantly controlled by hydrological processes. A future challenge will be to test this general framework in marine and freshwater habitats by quantifying the interactions between the functional traits of species and the water–sediment exchanges.
{"title":"The functional significance of bioturbation and biodeposition on biogeochemical processes at the water–sediment interface in freshwater and marine ecosystems","authors":"F. Mermillod‐Blondin","doi":"10.1899/10-121.1","DOIUrl":"https://doi.org/10.1899/10-121.1","url":null,"abstract":"Abstract Benthic invertebrates have important ecosystem engineering functions (bioturbation and biodeposition) in freshwater and marine benthic systems. Bioturbation and biodeposition affect the metabolism of the water–sediment interface through modification of water–sediment fluxes or organic-matter enrichment of sediments by biodeposits. The functional significance of these processes depends strongly on the type of invertebrate activities (the functional traits of the invertebrates) and on the modulation of this activity by environmental conditions. The aim of my article is to propose a common framework for the role of bioturbation/biodeposition in benthic habitats of both marine and freshwater environments. In these ecosystems, hydrological exchanges between the water and sediments (interstitial flow rates) control the microbial activity inside sediments. The ability of ecosystem engineers to influence benthic microbial processes differs strongly between diffusion-dominated (low interstitial flow rates) and advection-dominated (high interstitial flow rates) habitats. Bioturbation/biodeposition may play a role in diffusion-dominated habitats where invertebrates can significantly modify water and particle fluxes at the water–sediment interface, whereas a slight influence of ecosystem engineers is expected in advection-dominated habitats where fluxes are predominantly controlled by hydrological processes. A future challenge will be to test this general framework in marine and freshwater habitats by quantifying the interactions between the functional traits of species and the water–sediment exchanges.","PeriodicalId":49987,"journal":{"name":"Journal of the North American Benthological Society","volume":"50 1","pages":"770 - 778"},"PeriodicalIF":0.0,"publicationDate":"2011-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80821127","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 Exudates are ubiquitous in marine and fresh waters. They include Extracellular Polymeric Substances (EPS; including mucus, slimes, and biofilm matrices), silk, and chitin. EPS have many uses for the organisms that produce them—attachment, locomotion, feeding, and protection. They also act as glues to bind other materials, including the egesta within fecal pellets. Silk, an exudate produced only in fresh waters, is used in tube construction, to make nets used in feeding, and as a means of attachment. Chitin is the basis of the peritrophic matrix that surrounds the gut contents of some invertebrates and may act as a binding surrounding their fecal pellets. EPS are found free in the water column and in and on the substratum, as well as in close contact with the organisms that exude them. Free EPS have an essential role in particle formation and aggregation, processes that have been studied primarily in marine systems. Like EPS, silk is highly adsorptive and is found free within substrata, but rarely in the water column. Understanding the role of exudates requires collaboration between marine and freshwater biologists, physical geographers, and chemists, especially those working on surface processes and colloids. The results of these collaborations should expand our understanding of the many vital roles played by exudates in aquatic ecosystems.
{"title":"EPS (Extracellular Polymeric Substances), silk, and chitin: vitally important exudates in aquatic ecosystems","authors":"R. Wotton","doi":"10.1899/10-120.1","DOIUrl":"https://doi.org/10.1899/10-120.1","url":null,"abstract":"Abstract Exudates are ubiquitous in marine and fresh waters. They include Extracellular Polymeric Substances (EPS; including mucus, slimes, and biofilm matrices), silk, and chitin. EPS have many uses for the organisms that produce them—attachment, locomotion, feeding, and protection. They also act as glues to bind other materials, including the egesta within fecal pellets. Silk, an exudate produced only in fresh waters, is used in tube construction, to make nets used in feeding, and as a means of attachment. Chitin is the basis of the peritrophic matrix that surrounds the gut contents of some invertebrates and may act as a binding surrounding their fecal pellets. EPS are found free in the water column and in and on the substratum, as well as in close contact with the organisms that exude them. Free EPS have an essential role in particle formation and aggregation, processes that have been studied primarily in marine systems. Like EPS, silk is highly adsorptive and is found free within substrata, but rarely in the water column. Understanding the role of exudates requires collaboration between marine and freshwater biologists, physical geographers, and chemists, especially those working on surface processes and colloids. The results of these collaborations should expand our understanding of the many vital roles played by exudates in aquatic ecosystems.","PeriodicalId":49987,"journal":{"name":"Journal of the North American Benthological Society","volume":"53 1","pages":"762 - 769"},"PeriodicalIF":0.0,"publicationDate":"2011-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83130037","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}
A. Rober, Kevin H. Wyatt, R. Stevenson, And R Jan Stevenson
Abstract We evaluated the potential for grazers to regulate benthic algal biomass and taxonomic composition in an Alaskan marsh after enrichment with nutrients that are expected to increase in the region with ongoing climate change. We nested caged and uncaged substrates together inside mesocosm enclosures with natural abundances of snails or no snails and with or without nutrient enrichment (NO3 + PO4 + Si). Algal biomass was greater in all nutrient-enriched enclosures than in controls. Algal biomass was greater in enclosures where grazers were present but excluded by a cage than in enclosures where grazers were allowed to graze or where grazers were absent. In the presence of nutrients, grazed communities were dominated by small coccoid green algae and cyanobacteria, which were overgrown by filamentous green algae when grazers were excluded. In the absence of nutrients, grazers had little effect on algal biomass or taxonomic composition. However, grazers recycled a small but potentially important amount of nutrients in their waste, suggesting that consumer-driven nutrient recycling may have played a role in maintaining algal biomass when grazers were present. Our data show that grazers regulate algal responses to nutrients by suppressing algal accumulation but increasing productivity through nutrient recycling in a northern boreal wetland.
{"title":"Regulation of algal structure and function by nutrients and grazing in a boreal wetland","authors":"A. Rober, Kevin H. Wyatt, R. Stevenson, And R Jan Stevenson","doi":"10.1899/10-166R.1","DOIUrl":"https://doi.org/10.1899/10-166R.1","url":null,"abstract":"Abstract We evaluated the potential for grazers to regulate benthic algal biomass and taxonomic composition in an Alaskan marsh after enrichment with nutrients that are expected to increase in the region with ongoing climate change. We nested caged and uncaged substrates together inside mesocosm enclosures with natural abundances of snails or no snails and with or without nutrient enrichment (NO3 + PO4 + Si). Algal biomass was greater in all nutrient-enriched enclosures than in controls. Algal biomass was greater in enclosures where grazers were present but excluded by a cage than in enclosures where grazers were allowed to graze or where grazers were absent. In the presence of nutrients, grazed communities were dominated by small coccoid green algae and cyanobacteria, which were overgrown by filamentous green algae when grazers were excluded. In the absence of nutrients, grazers had little effect on algal biomass or taxonomic composition. However, grazers recycled a small but potentially important amount of nutrients in their waste, suggesting that consumer-driven nutrient recycling may have played a role in maintaining algal biomass when grazers were present. Our data show that grazers regulate algal responses to nutrients by suppressing algal accumulation but increasing productivity through nutrient recycling in a northern boreal wetland.","PeriodicalId":49987,"journal":{"name":"Journal of the North American Benthological Society","volume":"91 1","pages":"787 - 796"},"PeriodicalIF":0.0,"publicationDate":"2011-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89714256","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 literature regarding freshwater and marine exchanges of organic matter (OM) focuses predominantly on the unidirectional delivery of allochthonous and autochthonous material from freshwater to the marine environment. Another ecologically significant exchange occurs when anadromous organisms move into coastal and interior watersheds and bring marine-accrued OM and its incorporated marine-derived nutrients (MDN). We use the example of Pacific salmon streams to discuss bidirectional transfers of OM in the upstream and downstream directions with specific reference to the role of flocculation. A fish-floc feedback loop has recently been presented as a mechanism that allows transfer of salmon OM to the gravel-bed matrix in the form of flocs. In the proposed fish-floc feedback loop, the OM source is salmon, but the OM source will change with fish species. Once fish-based flocs enter the gravel bed they can be stored or used by benthic organisms. A salmon disturbance regime that includes redistribution of gravel, fine sediment, and biofilm during redd construction and release of salmon OM to the stream is integral to the fish-floc feedback loop because it provides the inorganic fine sediment and OM required for floc formation. The MDN subsidy provided by returning salmon is important for natal watershed functioning as illustrated by a conceptual OM feedback loop that links these freshwater and marine exchanges. Retention of floc-bound OM in the gravel bed afforded by settling flocs allows slower downstream transfer of nutrients en route to the ocean and a correspondingly increased period for uptake in food webs downstream.
{"title":"Bidirectional delivery of organic matter between freshwater and marine systems: the role of flocculation in Pacific salmon streams","authors":"E. Petticrew, J. Rex, S. Albers","doi":"10.1899/10-133.1","DOIUrl":"https://doi.org/10.1899/10-133.1","url":null,"abstract":"Abstract The literature regarding freshwater and marine exchanges of organic matter (OM) focuses predominantly on the unidirectional delivery of allochthonous and autochthonous material from freshwater to the marine environment. Another ecologically significant exchange occurs when anadromous organisms move into coastal and interior watersheds and bring marine-accrued OM and its incorporated marine-derived nutrients (MDN). We use the example of Pacific salmon streams to discuss bidirectional transfers of OM in the upstream and downstream directions with specific reference to the role of flocculation. A fish-floc feedback loop has recently been presented as a mechanism that allows transfer of salmon OM to the gravel-bed matrix in the form of flocs. In the proposed fish-floc feedback loop, the OM source is salmon, but the OM source will change with fish species. Once fish-based flocs enter the gravel bed they can be stored or used by benthic organisms. A salmon disturbance regime that includes redistribution of gravel, fine sediment, and biofilm during redd construction and release of salmon OM to the stream is integral to the fish-floc feedback loop because it provides the inorganic fine sediment and OM required for floc formation. The MDN subsidy provided by returning salmon is important for natal watershed functioning as illustrated by a conceptual OM feedback loop that links these freshwater and marine exchanges. Retention of floc-bound OM in the gravel bed afforded by settling flocs allows slower downstream transfer of nutrients en route to the ocean and a correspondingly increased period for uptake in food webs downstream.","PeriodicalId":49987,"journal":{"name":"Journal of the North American Benthological Society","volume":"6 1","pages":"779 - 786"},"PeriodicalIF":0.0,"publicationDate":"2011-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73787918","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 Former agricultural fields that are converted to wetlands can serve as either a source or a sink of P to connecting downstream water bodies. Understanding the P dynamics associated with these flooded fields can lead to appropriate mitigation strategies. We investigated P dynamics in flooded celery fields that are adjacent to and connect with a major tributary that eventually flows into Lake Michigan. We measured the P concentrations and loads in the tributary upstream and downstream of the flooded celery fields. Mean total P (TP) load was 2.6× greater downstream than upstream of the flooded celery fields. Turbidity, chlorophyll a, and soluble reactive P (SRP) concentration all were significantly greater at the downstream sampling site than at the upstream site. Mean water-column TP concentrations in the flooded celery fields ranged from 368 to 810 µg/L, compared to mean TP concentrations of 29 and 46 µg/L at the upstream and downstream sampling sites, respectively, in the tributary. Equilibrium P concentrations of flooded celery-field sediments were significantly greater than the water-column SRP concentrations, a result suggesting that the sediments were a source of P to the overlying water. Last, sediment pore-water concentrations of P were very high based on in-situ pore-water samplers, with maximum values of ∼1.6 mg/L. Our results show that wetlands converted from former agricultural fields can be a significant source of nutrients to downstream receiving water bodies. We recommend that the concentrations and release rates of sediment nutrients be measured before areas are converted to wetlands to ensure they serve as nutrient sinks instead of nutrient sources.
{"title":"Does converting agricultural fields to wetlands retain or release P?","authors":"A. Steinman, Mary E. Ogdahl","doi":"10.1899/10-106.1","DOIUrl":"https://doi.org/10.1899/10-106.1","url":null,"abstract":"Abstract Former agricultural fields that are converted to wetlands can serve as either a source or a sink of P to connecting downstream water bodies. Understanding the P dynamics associated with these flooded fields can lead to appropriate mitigation strategies. We investigated P dynamics in flooded celery fields that are adjacent to and connect with a major tributary that eventually flows into Lake Michigan. We measured the P concentrations and loads in the tributary upstream and downstream of the flooded celery fields. Mean total P (TP) load was 2.6× greater downstream than upstream of the flooded celery fields. Turbidity, chlorophyll a, and soluble reactive P (SRP) concentration all were significantly greater at the downstream sampling site than at the upstream site. Mean water-column TP concentrations in the flooded celery fields ranged from 368 to 810 µg/L, compared to mean TP concentrations of 29 and 46 µg/L at the upstream and downstream sampling sites, respectively, in the tributary. Equilibrium P concentrations of flooded celery-field sediments were significantly greater than the water-column SRP concentrations, a result suggesting that the sediments were a source of P to the overlying water. Last, sediment pore-water concentrations of P were very high based on in-situ pore-water samplers, with maximum values of ∼1.6 mg/L. Our results show that wetlands converted from former agricultural fields can be a significant source of nutrients to downstream receiving water bodies. We recommend that the concentrations and release rates of sediment nutrients be measured before areas are converted to wetlands to ensure they serve as nutrient sinks instead of nutrient sources.","PeriodicalId":49987,"journal":{"name":"Journal of the North American Benthological Society","volume":"498 1","pages":"820 - 830"},"PeriodicalIF":0.0,"publicationDate":"2011-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91167440","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}
Julie D. Alexander, B. Kerans, T. Koel, C. Rasmussen
Abstract Parasites can regulate host abundance and influence the composition and structure of communities. However, host–parasite interactions might be context-specific if environmental conditions can alter the outcome of parasitism and disease. An understanding of how host–parasite interactions might change in different contexts will be useful for predicting and managing disease against a background of anthropogenic environmental change. We examined the ecology of Myxobolus cerebralis, the parasite that causes whirling disease in salmonids, and its obligate host, Tubifex tubifex, in geothermally variable stream reaches in Yellowstone National Park. We identified reaches in 4 categories of geothermal influence, which were characterized by variable substrates, temperatures, specific conductivities, and pH. In each reach, we measured aspects of host ecology (abundance, relative abundance, size, and genotype of T. tubifex), parasite ecology (infection prevalence in T. tubifex and abundance of M. cerebralis-infected T. tubifex), and risk to fish of contracting whirling disease. Tubifex tubifex abundance was high all in reaches characterized by geothermal influence, whereas abundance of M. cerebralis-infected T. tubifex was high only in reaches characterized by intermediate geothermal influence. We suggest that habitat had a contextual effect on parasitism in the oligochaete host. Abundance of infected hosts appeared to depend on host abundance in all reach types except those with high geothermal influence, where abundance of infected hosts depended on environmental factors.
{"title":"Context-specific parasitism in Tubifex tubifex in geothermally influenced stream reaches in Yellowstone National Park","authors":"Julie D. Alexander, B. Kerans, T. Koel, C. Rasmussen","doi":"10.1899/10-043.1","DOIUrl":"https://doi.org/10.1899/10-043.1","url":null,"abstract":"Abstract Parasites can regulate host abundance and influence the composition and structure of communities. However, host–parasite interactions might be context-specific if environmental conditions can alter the outcome of parasitism and disease. An understanding of how host–parasite interactions might change in different contexts will be useful for predicting and managing disease against a background of anthropogenic environmental change. We examined the ecology of Myxobolus cerebralis, the parasite that causes whirling disease in salmonids, and its obligate host, Tubifex tubifex, in geothermally variable stream reaches in Yellowstone National Park. We identified reaches in 4 categories of geothermal influence, which were characterized by variable substrates, temperatures, specific conductivities, and pH. In each reach, we measured aspects of host ecology (abundance, relative abundance, size, and genotype of T. tubifex), parasite ecology (infection prevalence in T. tubifex and abundance of M. cerebralis-infected T. tubifex), and risk to fish of contracting whirling disease. Tubifex tubifex abundance was high all in reaches characterized by geothermal influence, whereas abundance of M. cerebralis-infected T. tubifex was high only in reaches characterized by intermediate geothermal influence. We suggest that habitat had a contextual effect on parasitism in the oligochaete host. Abundance of infected hosts appeared to depend on host abundance in all reach types except those with high geothermal influence, where abundance of infected hosts depended on environmental factors.","PeriodicalId":49987,"journal":{"name":"Journal of the North American Benthological Society","volume":"90 1","pages":"853 - 867"},"PeriodicalIF":0.0,"publicationDate":"2011-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88271506","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}
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