Abstract. Heterogeneity generated by irregularities on the surface of streambed substrates is an important determinant of local species diversity of algae. However, few investigators have examined the effects of substrate roughness on the composition of algal growth forms and on patterns of species distribution. We examined the influence of substrate roughness on stream benthic algal assemblages through a field experiment with 2 treatments (smooth and rough artificial substrates for algal colonization). We assessed whether species richness, density, and assemblage composition of benthic algae (all taxa and those in 5 growth-form groups) differed between treatments and whether differences in species composition between substrates were the result of species turnover or nestedness. We also used a data subsampling procedure to investigate the effect of differences in species richness between treatments. Total species richness was higher on rough than on smooth substrates, but density did not differ between treatments. Species richness, density, and composition of the adnate/prostrate growth form did not differ between treatments. The erect/stalked growth form had higher species richness on rough substrates, but did not differ in density between treatments. All other growth forms (filamentous, motile, and metaphyton) had higher species richness and density on rough substrates and differed in species composition between substrates. The results of the subsampling analysis indicated that assemblage composition was affected by differences in species richness and by changes in species composition (i.e., turnover). Species distribution had a nested pattern, in which the assemblages on smooth substrates were a subgroup of the species occurring on rough substrates. We suggest that the differences in assemblage composition between smooth and rough substrates resulted from variability in species' capabilities to colonize substrates with or without crevices. This variability resulted in both nestedness and turnover.
{"title":"Substrate roughness affects stream benthic algal diversity, assemblage composition, and nestedness","authors":"Fabiana Schneck, A. Schwarzbold, A. S. Melo","doi":"10.1899/11-044.1","DOIUrl":"https://doi.org/10.1899/11-044.1","url":null,"abstract":"Abstract. Heterogeneity generated by irregularities on the surface of streambed substrates is an important determinant of local species diversity of algae. However, few investigators have examined the effects of substrate roughness on the composition of algal growth forms and on patterns of species distribution. We examined the influence of substrate roughness on stream benthic algal assemblages through a field experiment with 2 treatments (smooth and rough artificial substrates for algal colonization). We assessed whether species richness, density, and assemblage composition of benthic algae (all taxa and those in 5 growth-form groups) differed between treatments and whether differences in species composition between substrates were the result of species turnover or nestedness. We also used a data subsampling procedure to investigate the effect of differences in species richness between treatments. Total species richness was higher on rough than on smooth substrates, but density did not differ between treatments. Species richness, density, and composition of the adnate/prostrate growth form did not differ between treatments. The erect/stalked growth form had higher species richness on rough substrates, but did not differ in density between treatments. All other growth forms (filamentous, motile, and metaphyton) had higher species richness and density on rough substrates and differed in species composition between substrates. The results of the subsampling analysis indicated that assemblage composition was affected by differences in species richness and by changes in species composition (i.e., turnover). Species distribution had a nested pattern, in which the assemblages on smooth substrates were a subgroup of the species occurring on rough substrates. We suggest that the differences in assemblage composition between smooth and rough substrates resulted from variability in species' capabilities to colonize substrates with or without crevices. This variability resulted in both nestedness and turnover.","PeriodicalId":49987,"journal":{"name":"Journal of the North American Benthological Society","volume":"58 1","pages":"1049 - 1056"},"PeriodicalIF":0.0,"publicationDate":"2011-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75286661","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. Island biogeography theory can be used to explain patterns of species richness on various types of habitat islands, including freshwater lake systems. Mollusk production in these systems also has been linked to various water-chemistry variables, such as pH, alkalinity, hardness, and specific conductance. We examined how mollusk diversity patterns were related to geographical and limnological factors in insular lakes of the Beaver and Manitou Archipelagos in Lake Michigan (Laurentian Great Lakes), USA. The strongest correlations observed were with shoreline development (r = 0.80), specific conductance (r = 0.87), and pH (r = 0.87). Principal components analysis revealed that isolation by distance and PO43− concentration also may have affected species richness and abundance. Shoreline length was a better predictor of species richness than surface area, but both measures of habitat size were unable to account for much of the variation in species richness. The data suggest that shoreline length and development represent available habitat area more accurately than lake area for primarily littoral-dwelling mollusks. The relatively weak correlations observed with lake area and isolation from Lake Michigan suggest that application of island biogeography theory to predict mollusk species richness using only lake surface area and isolation by distance is limited for freshwater mollusks.
摘要岛屿生物地理学理论可以用来解释包括淡水湖系统在内的各种生境岛屿物种丰富度的格局。这些系统中的软体动物产量也与各种水化学变量有关，如pH值、碱度、硬度和比电导。我们研究了美国密歇根湖(Laurentian Great lakes)海狸群岛和马尼托群岛岛屿湖泊中软体动物多样性格局与地理和湖泊因素的关系。相关性最强的是岸线发育(r = 0.80)、比电导(r = 0.87)和pH (r = 0.87)。主成分分析表明，距离隔离和PO43−浓度对物种丰富度和丰度也有影响。海岸线长度比地表面积更能预测物种丰富度，但这两种栖息地大小的测量都不能解释物种丰富度的大部分变化。这些数据表明，对于主要生活在沿海的软体动物来说，海岸线长度和发育情况比湖泊面积更准确地代表了可用的栖息地面积。与密歇根湖的湖泊面积和隔离度的相关性相对较弱，这表明仅利用湖泊面积和距离隔离来预测淡水软体动物物种丰富度的岛屿生物地理学理论是有限的。
{"title":"Insular lake island biogeography: using lake metrics to predict diversity in littoral zone mollusk communities","authors":"A. T. Harris, D. Woolnough, D. Zanatta","doi":"10.1899/11-020.1","DOIUrl":"https://doi.org/10.1899/11-020.1","url":null,"abstract":"Abstract. Island biogeography theory can be used to explain patterns of species richness on various types of habitat islands, including freshwater lake systems. Mollusk production in these systems also has been linked to various water-chemistry variables, such as pH, alkalinity, hardness, and specific conductance. We examined how mollusk diversity patterns were related to geographical and limnological factors in insular lakes of the Beaver and Manitou Archipelagos in Lake Michigan (Laurentian Great Lakes), USA. The strongest correlations observed were with shoreline development (r = 0.80), specific conductance (r = 0.87), and pH (r = 0.87). Principal components analysis revealed that isolation by distance and PO43− concentration also may have affected species richness and abundance. Shoreline length was a better predictor of species richness than surface area, but both measures of habitat size were unable to account for much of the variation in species richness. The data suggest that shoreline length and development represent available habitat area more accurately than lake area for primarily littoral-dwelling mollusks. The relatively weak correlations observed with lake area and isolation from Lake Michigan suggest that application of island biogeography theory to predict mollusk species richness using only lake surface area and isolation by distance is limited for freshwater mollusks.","PeriodicalId":49987,"journal":{"name":"Journal of the North American Benthological Society","volume":"498 ","pages":"1008 - 997"},"PeriodicalIF":0.0,"publicationDate":"2011-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1899/11-020.1","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72419398","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 goal of our study was to investigate the interaction between the invasive mussel Limnoperna fortunei and benthic invertebrate communities at different spatial scales and under different environmental conditions. We analyzed the effects of L. fortunei on benthic invertebrate communities at different downstream distances (meters) from mussel beds and compared these trends in 2 rivers characterized by dissimilar chemical disturbance levels. In areas distant from L. fortunei beds, invertebrate composition at the 2 rivers differed strongly, probably in response to different levels of environmental pollution. In areas near L. fortunei beds, invertebrate composition at the 2 rivers was similar, suggesting that golden mussels have strong homogenizing effects on faunal makeup. We also found that facilitation was species specific and, in contrast to the general paradigm, weaker (rather than stronger) under more stressful conditions. Our results show that understanding the effects of L. fortunei requires accounting for scale- and species-specific effects.
{"title":"Benthic community responses to invasion by the golden mussel, Limnoperna fortunei Dunker: biotic homogenization vs environmental driving forces","authors":"Paula Sardiña, E. Chaves, M. Marchese","doi":"10.1899/10-170.1","DOIUrl":"https://doi.org/10.1899/10-170.1","url":null,"abstract":"Abstract. The goal of our study was to investigate the interaction between the invasive mussel Limnoperna fortunei and benthic invertebrate communities at different spatial scales and under different environmental conditions. We analyzed the effects of L. fortunei on benthic invertebrate communities at different downstream distances (meters) from mussel beds and compared these trends in 2 rivers characterized by dissimilar chemical disturbance levels. In areas distant from L. fortunei beds, invertebrate composition at the 2 rivers differed strongly, probably in response to different levels of environmental pollution. In areas near L. fortunei beds, invertebrate composition at the 2 rivers was similar, suggesting that golden mussels have strong homogenizing effects on faunal makeup. We also found that facilitation was species specific and, in contrast to the general paradigm, weaker (rather than stronger) under more stressful conditions. Our results show that understanding the effects of L. fortunei requires accounting for scale- and species-specific effects.","PeriodicalId":49987,"journal":{"name":"Journal of the North American Benthological Society","volume":"26 1","pages":"1009 - 1023"},"PeriodicalIF":0.0,"publicationDate":"2011-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81708746","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. Our paper describes the ecological controls on algal-mat diatom communities in the dynamic stream ecosystems of the McMurdo Dry Valleys in Antarctica. Dry Valley diatom communities are relatively diverse, and nearly ½ of the taxa found in these mats are considered endemic. Diatom community composition was examined in 5 streams in Taylor Valley during a 15-y cooling period that included a discrete flood event. Two hydrologic variables, total annual discharge and historical variation in discharge, gave the most parsimonious model of among-stream and interannual variation in diatom communities. Algal-mat biomass and chlorophyll a concentrations decreased after the flood, which occurred during the 2001/2002 summer season. Most algal-mat diatom communities recovered quickly after the flood. However, Green Creek, a relatively high-flow stream with low historical variation in discharge, appears to have experienced a persistent diatom community shift toward increased relative abundance of small, generalist species. Diatom relative biovolume, a proxy for the size of diatoms within a sample, was negatively correlated with stream flow, such that higher-discharge streams contained greater relative abundances of smaller diatoms than lower-flow streams. Therefore, diatom size may play a role in determining the distribution of a species in these streams and may be useful for monitoring environmental changes. Our study demonstrates the importance of understanding factors affecting ecosystem resilience, especially in polar regions, which are experiencing rapid climate changes.
{"title":"Hydrologic processes influence diatom community composition in Dry Valley streams","authors":"L. Stanish, D. Nemergut, D. McKnight","doi":"10.1899/11-008.1","DOIUrl":"https://doi.org/10.1899/11-008.1","url":null,"abstract":"Abstract. Our paper describes the ecological controls on algal-mat diatom communities in the dynamic stream ecosystems of the McMurdo Dry Valleys in Antarctica. Dry Valley diatom communities are relatively diverse, and nearly ½ of the taxa found in these mats are considered endemic. Diatom community composition was examined in 5 streams in Taylor Valley during a 15-y cooling period that included a discrete flood event. Two hydrologic variables, total annual discharge and historical variation in discharge, gave the most parsimonious model of among-stream and interannual variation in diatom communities. Algal-mat biomass and chlorophyll a concentrations decreased after the flood, which occurred during the 2001/2002 summer season. Most algal-mat diatom communities recovered quickly after the flood. However, Green Creek, a relatively high-flow stream with low historical variation in discharge, appears to have experienced a persistent diatom community shift toward increased relative abundance of small, generalist species. Diatom relative biovolume, a proxy for the size of diatoms within a sample, was negatively correlated with stream flow, such that higher-discharge streams contained greater relative abundances of smaller diatoms than lower-flow streams. Therefore, diatom size may play a role in determining the distribution of a species in these streams and may be useful for monitoring environmental changes. Our study demonstrates the importance of understanding factors affecting ecosystem resilience, especially in polar regions, which are experiencing rapid climate changes.","PeriodicalId":49987,"journal":{"name":"Journal of the North American Benthological Society","volume":"29 1","pages":"1057 - 1073"},"PeriodicalIF":0.0,"publicationDate":"2011-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83584776","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}
M. K. Drinkard, M. Kershner, A. Romito, Julie E. Nieset, F. D. de Szalay
Abstract Flood-pulsing is a key environmental factor that structures biotic communities in large-order river systems, but we focused our study on the effects of flood-pulsing in headwater systems. We used 10 mesocosm wetlands (10 m × 20 m) to test 2 treatments: a flood-pulse regimen in which natural flood events caused water levels to fluctuate and a static regimen in which water levels remained artificially stable. Abiotic characteristics, plants, and aquatic invertebrate communities were monitored from 2002 through 2005 in permanent pools, nonflooded banks in static wetlands, and intermittently flooded banks in flood-pulse wetlands. The flood-pulse treatment had minimal effects on environmental conditions of permanent pools, and submersed plant and aquatic invertebrate communities in permanent pools were similar in both treatments. This result suggested that resource subsidies from the floodplain to the pools were minimal. However, flood-pulsing caused observable changes to plant communities in the intermittently flooded zone (IFZ) above the permanently flooded pool. Overall plant diversity was higher in static wetlands, and % bare ground was higher in flood-pulse wetlands, results suggesting that the short, stochastic floods were a strong environmental stressor. In flood-pulse wetlands, the fluctuating water levels may have reduced the proportion of introduced, weedy, and upland plant taxa. Flood-pulse and static wetlands had distinctly different plant assemblage compositions, indicating that the abiotic stressors caused pronounced changes in the floodplain community. An indicator species analysis showed that taxa classified as obligate wetland plants were indicators in flood-pulse wetlands (e.g., Juncus canadensis, Ludwigia palustris, Dulichium arundinaceum, Eleocharis obtusa, Carex crinita, Carex lupulina, Carex vulpinoidea), but taxa classified as facultative wetland or upland plants were indicators of static wetlands (Cirsium arvense, Eupatoriadelphus maculatus, Plantago lanceolata, Bidens frondosus, Melilotus officinalis, Mentha arvensis, Daucus carota, Poa palustris). Many functional categories of plant species that were common in flood-pulse wetlands (e.g., obligate wetland plants, perennial, native and nonweedy species) are considered beneficial from a management perspective.
{"title":"Responses of plants and invertebrate assemblages to water-level fluctuation in headwater wetlands","authors":"M. K. Drinkard, M. Kershner, A. Romito, Julie E. Nieset, F. D. de Szalay","doi":"10.1899/10-099.1","DOIUrl":"https://doi.org/10.1899/10-099.1","url":null,"abstract":"Abstract Flood-pulsing is a key environmental factor that structures biotic communities in large-order river systems, but we focused our study on the effects of flood-pulsing in headwater systems. We used 10 mesocosm wetlands (10 m × 20 m) to test 2 treatments: a flood-pulse regimen in which natural flood events caused water levels to fluctuate and a static regimen in which water levels remained artificially stable. Abiotic characteristics, plants, and aquatic invertebrate communities were monitored from 2002 through 2005 in permanent pools, nonflooded banks in static wetlands, and intermittently flooded banks in flood-pulse wetlands. The flood-pulse treatment had minimal effects on environmental conditions of permanent pools, and submersed plant and aquatic invertebrate communities in permanent pools were similar in both treatments. This result suggested that resource subsidies from the floodplain to the pools were minimal. However, flood-pulsing caused observable changes to plant communities in the intermittently flooded zone (IFZ) above the permanently flooded pool. Overall plant diversity was higher in static wetlands, and % bare ground was higher in flood-pulse wetlands, results suggesting that the short, stochastic floods were a strong environmental stressor. In flood-pulse wetlands, the fluctuating water levels may have reduced the proportion of introduced, weedy, and upland plant taxa. Flood-pulse and static wetlands had distinctly different plant assemblage compositions, indicating that the abiotic stressors caused pronounced changes in the floodplain community. An indicator species analysis showed that taxa classified as obligate wetland plants were indicators in flood-pulse wetlands (e.g., Juncus canadensis, Ludwigia palustris, Dulichium arundinaceum, Eleocharis obtusa, Carex crinita, Carex lupulina, Carex vulpinoidea), but taxa classified as facultative wetland or upland plants were indicators of static wetlands (Cirsium arvense, Eupatoriadelphus maculatus, Plantago lanceolata, Bidens frondosus, Melilotus officinalis, Mentha arvensis, Daucus carota, Poa palustris). Many functional categories of plant species that were common in flood-pulse wetlands (e.g., obligate wetland plants, perennial, native and nonweedy species) are considered beneficial from a management perspective.","PeriodicalId":49987,"journal":{"name":"Journal of the North American Benthological Society","volume":"40 1","pages":"981 - 996"},"PeriodicalIF":0.0,"publicationDate":"2011-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83567153","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 Urbanization is an important ecological modifier of stream catchments and significantly alters C type and concentration and heavy metal input to aquatic systems. C and heavy metals are important determinants of microbial community structure (population dynamics) and function (physiological processes). Understanding how changes at the landscape scale affect key nutrient-transformation processes (e.g., denitrification) and C metabolism (e.g., methanogenesis) at the micro scale requires simultaneous determination of the structural and functional responses of bacterial communities. We compared total bacterial (16S ribosomal ribonucleic acid [rRNA] gene) and denitrifying bacterial (nosZ gene) community structures in sediments taken from an urban and a nonurban stream before and after C and Zn additions. Microcosms containing stream sediment were supplemented with either proteinaceous or leaf-leachate C, increasing the C content by ∼36 and 130 mg/L, respectively. C was added in the presence and absence of Zn addition (200 mg/kg). Changes in community function were determined simultaneously with additions by measuring the rates of CO2, N2, and CH4 accumulation in the headspace of each mesocosm. Site had the greatest effect on total and denitrifying bacterial community structures. Added C caused a small but significant change in total bacterial community structure, but did not change denitrifying bacterial community structure. C enrichment caused a significant and rapid change in community function. Rates of methanogenesis were significantly higher at the nonurban than at the urban site and were significantly affected by C type (significant site × C interaction). Denitrification and CO2 production were unaffected by C additions but differed between sites. Zn addition changed total bacterial community structure but not denitrifying bacterial community structure. Zn affected the rate of methanogenesis, but the effect size was less than for C type. Community structures remained different between sites at the end of the study despite exposure to Zn concentrations that reflected conditions in urbanized streams and C sources that mimicked those from urban or nonurban streams. Our study supports previous observations that microbial community structure is strongly influenced by prior sediment history. The broader implication is that landscape-scale changes like urbanization alter other physical and chemical properties of the stream sediment that influence community structure more than the Zn or C concentrations in our study.
{"title":"Sediment bacterial community structure and function in response to C and Zn amendments: urban and nonurban streams","authors":"S. Perryman, G. Rees, M. Grace","doi":"10.1899/11-009.1","DOIUrl":"https://doi.org/10.1899/11-009.1","url":null,"abstract":"Abstract Urbanization is an important ecological modifier of stream catchments and significantly alters C type and concentration and heavy metal input to aquatic systems. C and heavy metals are important determinants of microbial community structure (population dynamics) and function (physiological processes). Understanding how changes at the landscape scale affect key nutrient-transformation processes (e.g., denitrification) and C metabolism (e.g., methanogenesis) at the micro scale requires simultaneous determination of the structural and functional responses of bacterial communities. We compared total bacterial (16S ribosomal ribonucleic acid [rRNA] gene) and denitrifying bacterial (nosZ gene) community structures in sediments taken from an urban and a nonurban stream before and after C and Zn additions. Microcosms containing stream sediment were supplemented with either proteinaceous or leaf-leachate C, increasing the C content by ∼36 and 130 mg/L, respectively. C was added in the presence and absence of Zn addition (200 mg/kg). Changes in community function were determined simultaneously with additions by measuring the rates of CO2, N2, and CH4 accumulation in the headspace of each mesocosm. Site had the greatest effect on total and denitrifying bacterial community structures. Added C caused a small but significant change in total bacterial community structure, but did not change denitrifying bacterial community structure. C enrichment caused a significant and rapid change in community function. Rates of methanogenesis were significantly higher at the nonurban than at the urban site and were significantly affected by C type (significant site × C interaction). Denitrification and CO2 production were unaffected by C additions but differed between sites. Zn addition changed total bacterial community structure but not denitrifying bacterial community structure. Zn affected the rate of methanogenesis, but the effect size was less than for C type. Community structures remained different between sites at the end of the study despite exposure to Zn concentrations that reflected conditions in urbanized streams and C sources that mimicked those from urban or nonurban streams. Our study supports previous observations that microbial community structure is strongly influenced by prior sediment history. The broader implication is that landscape-scale changes like urbanization alter other physical and chemical properties of the stream sediment that influence community structure more than the Zn or C concentrations in our study.","PeriodicalId":49987,"journal":{"name":"Journal of the North American Benthological Society","volume":"62 1","pages":"951 - 962"},"PeriodicalIF":0.0,"publicationDate":"2011-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84659039","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}
J. Pozo, J. Casas, M. Menéndez, Salvador Mollá, I. Arostegui, A. Basaguren, Carmen M. Casado, E. Descals, J. García-Avilés, J. M. González, A. Larrañaga, E. López, Mirian Lusi, Ó. Moya, J. Pérez, T. Riera, Neftalí Roblas, M. Salinas
Abstract The main purpose of our work was to elucidate factors responsible for the geographical differences in leaf-litter decomposition rates in Spanish oligotrophic headwater streams. Decomposition experiments with alder (Alnus glutinosa) leaf litter were carried out in 22 headwater streams in 4 different climatic regions across the Iberian Peninsula (Cornisa Cantábrica, Cordillera Litoral Catalana, Sierra de Guadarrama, and Sierra Nevada). Streams that were similar in size, flowed mainly over siliceous substrate in catchments with scarce human settlements and activities, and fell within a range of low nutrient concentrations were chosen in each region. Breakdown rates were regionally variable and were low (0.109–0.198% ash-free dry mass [AFDM]/degree day [dd]) in the Cornisa Cantábrica, the most mesic and Atlantic region, and high (0.302–0.639% AFDM/dd) in Sierra de Guadarrama, one of the coldest and most inland areas. Temperature was not the determining factor affecting differences in breakdown rates among regions, and breakdown rates were not related to concentrations of dissolved nutrients. However, microbial reproductive activity (sporulation rates) was significantly correlated with dissolved P concentration. Breakdown rates were explained better by presence and feeding activities of detritivores than by decomposer activity. Incorporation of breakdown rates in assessment schemes of stream ecological status will be difficult because leaf processing does not respond unequivocally to environmental factors when climatic regions are considered. Thus, regional adjustments of baseline standards in reference conditions will be required.
摘要本研究的主要目的是阐明西班牙少营养源流凋落叶分解速率地理差异的影响因素。在伊比利亚半岛4个不同气候区(Cornisa Cantábrica、Cordillera Litoral Catalana、Sierra de Guadarrama和Sierra Nevada)的22条水源中进行了桤木(Alnus glutinosa)凋落叶分解实验。在每个区域选择的河流大小相似，主要在人类住区和活动稀少的集水区流过硅质基质，并且在低营养浓度范围内。分解率存在区域差异，在corisa Cantábrica(最湿润和大西洋地区)低(0.109-0.198%无灰干质量[AFDM]/度日[dd])，在Sierra de Guadarrama(最寒冷和最内陆地区之一)高(0.302-0.639% AFDM/度日)。温度不是影响区域间分解率差异的决定性因素，分解率与溶解营养物浓度无关。微生物繁殖活性(产孢率)与溶磷浓度显著相关。分解率用腐食动物的存在和摄食活动比用分解者的活动更能解释。在河流生态状况评估方案中纳入分解率将是困难的，因为当考虑气候区域时，树叶加工并不明确地响应环境因素。因此，需要在参考条件下对基准标准进行区域调整。
{"title":"Leaf-litter decomposition in headwater streams: a comparison of the process among four climatic regions","authors":"J. Pozo, J. Casas, M. Menéndez, Salvador Mollá, I. Arostegui, A. Basaguren, Carmen M. Casado, E. Descals, J. García-Avilés, J. M. González, A. Larrañaga, E. López, Mirian Lusi, Ó. Moya, J. Pérez, T. Riera, Neftalí Roblas, M. Salinas","doi":"10.1899/10-153.1","DOIUrl":"https://doi.org/10.1899/10-153.1","url":null,"abstract":"Abstract The main purpose of our work was to elucidate factors responsible for the geographical differences in leaf-litter decomposition rates in Spanish oligotrophic headwater streams. Decomposition experiments with alder (Alnus glutinosa) leaf litter were carried out in 22 headwater streams in 4 different climatic regions across the Iberian Peninsula (Cornisa Cantábrica, Cordillera Litoral Catalana, Sierra de Guadarrama, and Sierra Nevada). Streams that were similar in size, flowed mainly over siliceous substrate in catchments with scarce human settlements and activities, and fell within a range of low nutrient concentrations were chosen in each region. Breakdown rates were regionally variable and were low (0.109–0.198% ash-free dry mass [AFDM]/degree day [dd]) in the Cornisa Cantábrica, the most mesic and Atlantic region, and high (0.302–0.639% AFDM/dd) in Sierra de Guadarrama, one of the coldest and most inland areas. Temperature was not the determining factor affecting differences in breakdown rates among regions, and breakdown rates were not related to concentrations of dissolved nutrients. However, microbial reproductive activity (sporulation rates) was significantly correlated with dissolved P concentration. Breakdown rates were explained better by presence and feeding activities of detritivores than by decomposer activity. Incorporation of breakdown rates in assessment schemes of stream ecological status will be difficult because leaf processing does not respond unequivocally to environmental factors when climatic regions are considered. Thus, regional adjustments of baseline standards in reference conditions will be required.","PeriodicalId":49987,"journal":{"name":"Journal of the North American Benthological Society","volume":"124 1","pages":"935 - 950"},"PeriodicalIF":0.0,"publicationDate":"2011-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77089637","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 Freshwater mussels are one of the most imperiled groups of animals in North America. Effective resource management and conservation efforts require reliable estimates of species diversity and their distributions. However, sampling protocols for qualitative mussel surveys have not been well established and tested. Furthermore, the sampling effort required for a given data-quality goal (90% of species captured) often varies substantially among sites, and application of a standard effort probably would introduce bias into assemblage comparisons. We tested the sampling adequacy of time-based hand searches. We conducted 16-man-hour (mh) searches at each of 18 wadeable stream sites in Illinois that differed widely in environmental factors and historical species diversity and collected 27 to 942 individuals and 5 to 18 species per site. We accounted for imperfect species detectability by using the Chao-1 richness estimator and measured sampling adequacy as the % of the estimated number of species sampled. Four-mh searches, a frequently used effort, captured 15 to 100% of all species with an average of 61%, and yielded estimates of richness that were not significantly correlated with the estimated total richness (Pearson's r = 0.39, p > 0.05). Ten-mh searches captured >70% of all species at >70% of sites and resulted in a significant correlation between observed and estimated richness (Pearson's r ≥ 0.78, p < 0.01). A Random Forests (RF) model based on watershed and habitat characteristics (e.g., stream size and dominant substrate types) accounted for 45% of the variance in sampling adequacy of 4-mh searches. Sampling adequacy decreased with increasing stream size and substrate size but increased with % forest in the riparian zone and logs in the stream. A 2nd RF model was developed to predict the number of man-hours required to capture 70 ± 3% of all species, and it accounted for 37% of the variance. Our findings should serve as a guide for setting standard sampling efforts for mussel surveys in Illinois and probably other midwestern states and should provide a baseline for setting site-specific efforts. Our modeling approach is of general applicability for addressing sampling-adequacy issues in studies of any assemblage.
淡水贻贝是北美最濒危的动物群体之一。有效的资源管理和保护工作需要对物种多样性及其分布进行可靠的估计。然而，定性贻贝调查的抽样方案尚未很好地建立和测试。此外，给定数据质量目标(捕获物种的90%)所需的采样努力通常在不同地点之间有很大差异，并且应用标准努力可能会在组合比较中引入偏差。我们测试了基于时间的手部搜索的抽样充分性。我们在伊利诺伊州18个环境因素和历史物种多样性差异很大的可涉水溪流地点进行了16个工时(mh)的搜索，每个地点收集了27 ~ 942个个体和5 ~ 18个物种。我们使用Chao-1丰富度估计值和测量的采样充分性作为估计的采样物种数量的百分比来解释不完全物种可检测性。4 -mh搜索是一种常用的搜索方法，它捕获了所有物种的15%至100%，平均为61%，并且得出的丰富度估估值与估计的总丰富度不显著相关(Pearson’s r = 0.39, p > 0.05)。10 -mh搜索在70%以上的地点捕获了70%以上的物种，并且观测到的丰富度与估计的丰富度之间存在显著的相关性(Pearson’s r≥0.78,p < 0.01)。基于流域和生境特征(如河流大小和主要基质类型)的随机森林(RF)模型占4-mh搜索样本充分性方差的45%。采样充分性随河流大小和基质大小的增加而降低，但随河岸带森林和河流中原木的增加而增加。第二个RF模型用于预测捕获所有物种的70±3%所需的工时，它占方差的37%。我们的研究结果应该作为伊利诺斯州和其他中西部州贻贝调查的标准采样工作的指南，并为设定特定地点的工作提供基线。我们的建模方法一般适用于解决任何组合研究中的抽样充分性问题。
{"title":"Assessing sampling adequacy of mussel diversity surveys in wadeable Illinois streams","authors":"Jian Huang, Yong Cao, K. Cummings","doi":"10.1899/10-172.1","DOIUrl":"https://doi.org/10.1899/10-172.1","url":null,"abstract":"Abstract Freshwater mussels are one of the most imperiled groups of animals in North America. Effective resource management and conservation efforts require reliable estimates of species diversity and their distributions. However, sampling protocols for qualitative mussel surveys have not been well established and tested. Furthermore, the sampling effort required for a given data-quality goal (90% of species captured) often varies substantially among sites, and application of a standard effort probably would introduce bias into assemblage comparisons. We tested the sampling adequacy of time-based hand searches. We conducted 16-man-hour (mh) searches at each of 18 wadeable stream sites in Illinois that differed widely in environmental factors and historical species diversity and collected 27 to 942 individuals and 5 to 18 species per site. We accounted for imperfect species detectability by using the Chao-1 richness estimator and measured sampling adequacy as the % of the estimated number of species sampled. Four-mh searches, a frequently used effort, captured 15 to 100% of all species with an average of 61%, and yielded estimates of richness that were not significantly correlated with the estimated total richness (Pearson's r = 0.39, p > 0.05). Ten-mh searches captured >70% of all species at >70% of sites and resulted in a significant correlation between observed and estimated richness (Pearson's r ≥ 0.78, p < 0.01). A Random Forests (RF) model based on watershed and habitat characteristics (e.g., stream size and dominant substrate types) accounted for 45% of the variance in sampling adequacy of 4-mh searches. Sampling adequacy decreased with increasing stream size and substrate size but increased with % forest in the riparian zone and logs in the stream. A 2nd RF model was developed to predict the number of man-hours required to capture 70 ± 3% of all species, and it accounted for 37% of the variance. Our findings should serve as a guide for setting standard sampling efforts for mussel surveys in Illinois and probably other midwestern states and should provide a baseline for setting site-specific efforts. Our modeling approach is of general applicability for addressing sampling-adequacy issues in studies of any assemblage.","PeriodicalId":49987,"journal":{"name":"Journal of the North American Benthological Society","volume":"102 1","pages":"923 - 934"},"PeriodicalIF":0.0,"publicationDate":"2011-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75722988","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 Headwaters (stream orders 1–2) traditionally have been considered depauperate compared to mid-order streams (orders 3–4)—a conclusion that arises from a perception of streams as linear systems and emphasizes change in average &agr; (local) diversity along streams. We hypothesized an opposite pattern for &bgr; (among-site) diversity and suggest that headwaters might account for a large degree of basin-scale biodiversity if considered within the more realistic framework of streams as branching networks. We assembled pre-existing biodiversity data from across the globe to test this hypothesis broadly at the population-genetic (mitochondrial haplotype diversity within species) and community (species/taxonomic diversity) levels, with a focus on macroinvertebrates. We standardized 18 (9 headwater and 9 mid-order) population-genetic and 16 (10 headwater and 6 mid-order) community-level ecoregional data sets from 5 global ecozones for robust comparisons of &bgr;-diversity estimates between the 2 stream-size categories. At the population-genetic level, we applied measures of among-site variation commonly used at both population-genetic (FST and &PHgr;ST) and community (Sørensen's dissimilarity with both presence/absence and abundance data) levels and developed a novel strategy to compare expected rates of loss of &ggr; (regional) diversity as individual sites are eliminated sequentially from regions. At the community level, we limited analyses to Sørensen's presence/absence measures. We found that Sørensen's dissimilarity was significantly greater among headwaters than among mid-order streams at both population-genetic and community levels. We also showed that individual headwater reaches accounted for greater proportions of genetic &ggr; diversity than did mid-order reaches. However, neither FST nor &PHgr;ST was significantly different between stream-size categories. These measures, which have been used traditionally for comparisons of population-genetic variation, measure proportions of total variation rather than solely among-site variation (i.e., they also are influenced by within-site variation). In contrast, Sørensen's dissimilarity measures only among-site variation and, therefore, is presumably more useful for reflecting general &bgr; diversity. Overall results suggest that, on average, headwaters probably contribute disproportionately to biodiversity at the network scale. This finding demands a shift in thinking about the biodiversity contributions of small headwaters and has strong conservation implications for imperiled headwater streams around the world.
{"title":"Small but mighty: headwaters are vital to stream network biodiversity at two levels of organization","authors":"D. Finn, N. Bonada, Cesc Múrria, J. Hughes","doi":"10.1899/11-012.1","DOIUrl":"https://doi.org/10.1899/11-012.1","url":null,"abstract":"Abstract Headwaters (stream orders 1–2) traditionally have been considered depauperate compared to mid-order streams (orders 3–4)—a conclusion that arises from a perception of streams as linear systems and emphasizes change in average &agr; (local) diversity along streams. We hypothesized an opposite pattern for &bgr; (among-site) diversity and suggest that headwaters might account for a large degree of basin-scale biodiversity if considered within the more realistic framework of streams as branching networks. We assembled pre-existing biodiversity data from across the globe to test this hypothesis broadly at the population-genetic (mitochondrial haplotype diversity within species) and community (species/taxonomic diversity) levels, with a focus on macroinvertebrates. We standardized 18 (9 headwater and 9 mid-order) population-genetic and 16 (10 headwater and 6 mid-order) community-level ecoregional data sets from 5 global ecozones for robust comparisons of &bgr;-diversity estimates between the 2 stream-size categories. At the population-genetic level, we applied measures of among-site variation commonly used at both population-genetic (FST and &PHgr;ST) and community (Sørensen's dissimilarity with both presence/absence and abundance data) levels and developed a novel strategy to compare expected rates of loss of &ggr; (regional) diversity as individual sites are eliminated sequentially from regions. At the community level, we limited analyses to Sørensen's presence/absence measures. We found that Sørensen's dissimilarity was significantly greater among headwaters than among mid-order streams at both population-genetic and community levels. We also showed that individual headwater reaches accounted for greater proportions of genetic &ggr; diversity than did mid-order reaches. However, neither FST nor &PHgr;ST was significantly different between stream-size categories. These measures, which have been used traditionally for comparisons of population-genetic variation, measure proportions of total variation rather than solely among-site variation (i.e., they also are influenced by within-site variation). In contrast, Sørensen's dissimilarity measures only among-site variation and, therefore, is presumably more useful for reflecting general &bgr; diversity. Overall results suggest that, on average, headwaters probably contribute disproportionately to biodiversity at the network scale. This finding demands a shift in thinking about the biodiversity contributions of small headwaters and has strong conservation implications for imperiled headwater streams around the world.","PeriodicalId":49987,"journal":{"name":"Journal of the North American Benthological Society","volume":"2006 1","pages":"963 - 980"},"PeriodicalIF":0.0,"publicationDate":"2011-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86983257","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 Establishment of dreissenid mussels in aquatic systems is often accompanied by major changes in the abundance, diversity, and community composition of benthic invertebrates. However, few studies have been published that address the effects of long-term dreissenid presence on the littoral benthos inhabiting hard substrata in lakes. We present the results of a depth-stratified, quantitative survey of littoral benthos conducted at 4 sites in 1993, just before dreissenid invasion, and in 2008, 14 y after the establishment of dreissenids in Lake Simcoe, Ontario. Average densities of nondreissenid invertebrates were 45× greater in 2008 than in 1993. Amphipods, isopods, chironomids and oligochaetes underwent the largest increases in absolute abundance. The taxonomic diversity of the benthic invertebrate community (&agr; diversity) increased significantly. Community structure was more similar within and between depths and sites in 2008 than in 1993, a result implying lower &bgr; diversity of the postdreissenid littoral benthos. In addition, fewer differences were found in the densities of organisms between sampling locations in 2008 than in 1993. We suggest that dreissenids increase resource availability to benthic organisms and homogenize the littoral benthos by increasing the evenness of the distribution of food and physical-habitat resources across sites and depths. The transformation of the littoral benthic community of Lake Simcoe reflects a major change in the distribution of energy in the lake and is consistent with a dreissenid-mediated redirection of production from the pelagic to the littoral zone.
{"title":"Fourteen years of dreissenid presence in the rocky littoral zone of a large lake: effects on macroinvertebrate abundance and diversity","authors":"T. Ozersky, D. Barton, David O. Evans","doi":"10.1899/10-122.1","DOIUrl":"https://doi.org/10.1899/10-122.1","url":null,"abstract":"Abstract Establishment of dreissenid mussels in aquatic systems is often accompanied by major changes in the abundance, diversity, and community composition of benthic invertebrates. However, few studies have been published that address the effects of long-term dreissenid presence on the littoral benthos inhabiting hard substrata in lakes. We present the results of a depth-stratified, quantitative survey of littoral benthos conducted at 4 sites in 1993, just before dreissenid invasion, and in 2008, 14 y after the establishment of dreissenids in Lake Simcoe, Ontario. Average densities of nondreissenid invertebrates were 45× greater in 2008 than in 1993. Amphipods, isopods, chironomids and oligochaetes underwent the largest increases in absolute abundance. The taxonomic diversity of the benthic invertebrate community (&agr; diversity) increased significantly. Community structure was more similar within and between depths and sites in 2008 than in 1993, a result implying lower &bgr; diversity of the postdreissenid littoral benthos. In addition, fewer differences were found in the densities of organisms between sampling locations in 2008 than in 1993. We suggest that dreissenids increase resource availability to benthic organisms and homogenize the littoral benthos by increasing the evenness of the distribution of food and physical-habitat resources across sites and depths. The transformation of the littoral benthic community of Lake Simcoe reflects a major change in the distribution of energy in the lake and is consistent with a dreissenid-mediated redirection of production from the pelagic to the littoral zone.","PeriodicalId":49987,"journal":{"name":"Journal of the North American Benthological Society","volume":"3 1","pages":"913 - 922"},"PeriodicalIF":0.0,"publicationDate":"2011-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91098308","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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