The Experts below are selected from a list of 309 Experts worldwide ranked by ideXlab platform
Maile C Neel - One of the best experts on this subject based on the ideXlab platform.
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limited pollen dispersal small genetic neighborhoods and biparental inbreeding in Vallisneria Americana
American Journal of Botany, 2018Co-Authors: Michael W Lloyd, Hayley R Tumas, Maile C NeelAbstract:PREMISE OF THE STUDY: Pollen dispersal is a key process that influences ecological and evolutionary dynamics of plant populations by facilitating sexual reproduction and gene flow. Habitat loss and fragmentation have the potential to reduce pollen dispersal within and among habitat patches. We assessed aquatic pollen dispersal and mating system characteristics in Vallisneria Americana-a water-pollinated plant with a distribution that has been reduced from historic levels. METHODS: We examined pollen neighborhood size, biparental inbreeding, and pollen dispersal, based on seed paternity using the indirect paternity method KinDist, from samples of 18-39 mothers and 14-20 progeny per mother from three sites across 2 years. KEY RESULTS: On average, fruits contained seeds sired by seven fathers. We found significant biparental inbreeding and limited pollen dispersal distances (0.8-4.34 m). However, in a number of cases, correlated paternity did not decline with distance, and dispersal could not be reliably estimated. CONCLUSIONS: Frequent pollen dispersal is not expected among patches, and even within patches, gene flow via pollen will be limited. Limited pollen dispersal establishes genetic neighborhoods, which, unless overcome by seed and propagule dispersal, will lead to genetic differentiation even in a continuous population. Unless loss and fragmentation drive populations to extreme sex bias, local pollen dispersal is likely to be unaffected by habitat loss and fragmentation per se because the spatial scale of patch isolation already exceeds pollen dispersal distances. Therefore, managing specifically for pollen connectivity is only relevant over very short distances.
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genetic rescue versus outbreeding depression in Vallisneria Americana implications for mixing seed sources for restoration
Biological Conservation, 2013Co-Authors: Brittany W Marsden, Katharina A M Engelhardt, Maile C NeelAbstract:The selection of seed stock for restoration remains a complex issue. Using local stock reduces the chances of outbreeding depression or genetic dilution, whereas mixing sources may increase diversity and counteract inbreeding depression. Evaluation of these opposing approaches remains difficult when planning a restoration project but is needed to increase chances of long-term population persistence. We evaluated seed production and germination success of seeds from controlled reproductive crosses of the submersed aquatic plant Vallisneria Americana (wild celery) collected from populations throughout the Chesapeake Bay. We assessed differences in seeds, capsules, and germination success in three types of crosses: (1) individuals within-populations, (2) among-populations but within-genetically differentiated regions, and (3) among-regions. We observed population level differences in within-population and among-region crosses. Levels of genetic relatedness among individuals, genetic diversity within populations, or differentiation across populations did not predict reproductive success. Our data show that mixing sources from different populations and regions has both benefits and drawbacks. Thus, minimizing the risks of outbreeding and inbreeding depression, presented as a mostly dichotomous issue in the restoration literature, is not an either-or issue in V. Americana.
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does genetic diversity of restored sites differ from natural sites a comparison of Vallisneria Americana hydrocharitaceae populations within the chesapeake bay
Conservation Genetics, 2012Co-Authors: Michael W Lloyd, Katharina A M Engelhardt, Robert K Burnett, Maile C NeelAbstract:The goal of ecological restoration is to re-establish self-sustaining ecosystems that will resist future perturbation without additional human input. We focus here on the re-establishment of submersed aquatic macrophyte beds in the restoration of the Chesapeake Bay estuary. Degraded environmental conditions are often to blame for poor bed establishment, but genetic factors could also be contributing to low survival. We quantified the effect of restoration practices on genetic diversity in the submersed aquatic plant species Vallisneria Americana Michx. (Hydrocharitaceae) in the Chesapeake Bay. In 2007, we collected 440 shoots from 8 restored/natural site pairs and 4 restoration stock repositories, and genotyped those individuals at 10 microsatellite loci. Restoration practices do not appear to negatively impact genetic diversity, and basic measures of genetic diversity within restored sites overlap with natural sites. However, small population size of restored sites, significant inbreeding coefficients within 3 sites, and low overlap of allele composition among sites provide cause for concern. These problems are relatively minor, and we propose several corrections that would alleviate them altogether. Managers should be encouraged by our findings as well as the current state of the genetic diversity within V. Americana restoration efforts.
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development of 11 polymorphic microsatellite markers in a macrophyte of conservation concern Vallisneria Americana michaux hydrocharitaceae
Molecular Ecology Resources, 2009Co-Authors: Robert K Burnett, Katharina A M Engelhardt, Michael W Lloyd, Maile C NeelAbstract:: Vallisneria Americana Michaux (wild celery) is currently a target of submersed aquatic vegetation restoration efforts in the Chesapeake Bay watershed. To aid these efforts, we have developed 11 polymorphic microsatellite markers to assess the distribution and degree of genetic diversity in both restored and naturally occurring populations in the Chesapeake Bay. In 59 individuals from two populations, we detected two to 10 total alleles per locus. Observed heterozygosity ranged from 0.125 to 0.929, and two loci exhibited significant deviations from Hardy-Weinberg equilibrium in at least one of the populations assayed.
Jon Lovettdoust - One of the best experts on this subject based on the ideXlab platform.
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Vallisneria Americana hydrocharitaceae as a biomonitor of aquatic ecosystems comparison of cloned genotypes
American Journal of Botany, 1997Co-Authors: Maciej Biernacki, Jon LovettdoustAbstract:: We assessed the effects of local environment on survival, growth, and development in six clones (genotypes) of Vallisneria Americana grown at five sites in the Huron-Erie Corridor. Detrimental effects of local environment on plant performance (rate of clonal growth, leaf and root production, surface area of leaves and roots, plant biomass, rate of flowering, and turion production) were correlated with sediment toxicity and levels of organic contamination determined in independent studies, and differed among plant genotypes. All surviving clones used in the study ranked environmental quality of the five sites in the same order. Two genotypes, which were tolerant of contaminants, survived the 2 yr of exposure at all sites, while other nontolerant clones died within the 1st yr of study, at the two most contaminated sites. The leaf-to-root surface area ratio was highly indicative of site quality, and was not affected either by year-to-year variation, or by differences between genotypes. The use of cloned plants in this biomonitoring study reduced variance, and increased precision and accuracy of site assessment compared to biomonitoring with genetically variable plants. Clones of V. Americana tolerant of contaminants were particularly useful in assessing the most contaminated sites. An approach that uses an array of both tolerant and nontolerant clones is recommended.
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seed output and the seed bank in Vallisneria Americana hydrocharitaceae
American Journal of Botany, 1997Co-Authors: Cynthia Lokker, Lesley Lovettdoust, Jon LovettdoustAbstract:Seed banks and sexual reproduction are known to be significant in colonization and re-establishment of some aquatic macrophyte communities. For highly clonal aquatic macrophytes, however, there is a lack of information on seed production and seed fate as compared with annual sexual species. The seed bank for three populations of Vallisneria Americanain the Huron‐Erie corridor of the Great Lakes was sampled and quantified in the spring of 1994, and related to seed production in the previous season at these sites. Seed deposition rates during 1994 were also assessed. Sites varied in the proportion of plants flowering and in their tertiary sex ratios, but did not differ in seed numbers produced per unit area. The size of the seed bank was not significantly related to the previous season’s seed output, and estimates of seed deposition in the following year tended to be approximately tenfold greater than seed densities found in the seed bank. The stages between seed production and subsequent seed germination are generally very dynamic, with dispersal, mortality, and predation as likely regulating factors. The potential for seedling establishment in V. Americana needs to be assessed more fully before the role of seeds in population processes can be determined.
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laboratory assay of sediment phytotoxicity using the macrophyte Vallisneria Americana
Environmental Toxicology and Chemistry, 1997Co-Authors: Maciej Biernacki, Jon Lovettdoust, Lesley LovettdoustAbstract:In contrast to their ecological importance, submersed rooted macrophytes have been overlooked in environmental science. Presently, the array of standard phytotoxic bioassays includes only one free-floating vascular macrophyte (Lemna) and several algal species. A short-term and inexpensive assay was studied for feasibility in evaluating sediment quality. Cloned ramets of the macrophyte Vallisneria Americana were used to test phytotoxicity of sediments collected at different locations in the Detroit River. Ramets were planted in sediment samples and placed in greenhouse aquaria. After a week of exposure, ramets of V. Americana were destructively sampled and preserved. The leaf and root surfaces areas were determined, and plant biomass was recorded for each ramet. An index of the leaf-to-root surface area ratio was a reliable predictor of sediment phytotoxicity; the ratio of leaf-to-root mass was also useful but proved less consistent. Ramets grown in sediments that were relatively less contaminated with organic compounds had lower values of the leaf-to-root surface area ratio, while plants grown in more contaminated sediments had greater values. Results of analyses of variance indicated that the index of leaf-to-root surface area ratio responded to sediment quality but was not significantly affected by either variation in plant genotype or interaction between sediment and plant genotype. There was a significant correlation (p < 0.001) between rank-ordered results of the present greenhouse study and results of leaf-to-root surface area ratios for plants previously surveyed in the field.
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temporal biomonitoring using wild celery Vallisneria Americana
Journal of Great Lakes Research, 1997Co-Authors: Maciej Biernacki, Jon Lovettdoust, Lesley LovettdoustAbstract:Abstract This study was carried out to assess the effects of sediment type, local water column, source of plants, and duration of exposure between 1990 and 1994 upon growth, survivorship and reproduction of Vallisneria Americana at two sites in the Huron-Erie corridor of the Great Lakes. The major objective was to determine whether year-to-year variations affect consistency of results using Vallisneria as a biomonitoring tool. Relative annual rankings of results from experimental treatments did not change over a 4-year period. However, most of the absolute measures of plant performance varied significantly between years. Effects on plant growth and development were associated primarily with exposure to water columns, and secondarily to sediments. Measures of plant density, rate of clonal growth, leaf length, number of leaves per m 2 , and plant biomass per m 2 were unusually high in the first year compared with the subsequent 3 years, perhaps due to disturbance associated with set-up of the experiment. Leaf-to-root surface area ratios provided a simple, consistent, and reliable measure of environmental quality. Other measures of plant performance varied significantly from year-to-year and, therefore, are not advised for long-term comparisons. Results of this study indicate that Vallisneria can be an effective temporal biomonitor of environmental quality.
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Vallisneria Americana as a biomonitor of aquatic ecosystems leaf to root surface area ratios and organic contamination in the huron erie corridor
Journal of Great Lakes Research, 1996Co-Authors: Maciej Biernacki, Jon Lovettdoust, Lesley LovettdoustAbstract:Aquatic macrophytes are useful biomonitors of sub-lethal effects of organochlorine contamination. Ramets of Vallisneria Americana were sampled from natural populations at 243 sites in the Huron-Erie corridor in August 1993, and an index of leaf-to-root surface area ratios was determined. Sites were then ranked according to this index. Site rankings based on leaf-to-root surface area ratios were significantly correlated with the ranks of these sites using levels of organochlorine contamination of biota or sediment, reported independently in the published literature. The ratio of leaf-to-root surface areas ranged from 2 to 92, and higher values were found in more polluted sites. At four sites, plants were sampled monthly over one growing season, while at two sites plants were sampled each year for 4 years. The leaf-to-root surface area ratio changed little from year to year. At highly polluted sites there was a progressive increase in ratio over the growing season. Surveyed sites remained in the same relative ranking over the growing season, and a single survey within the same month could compare sites reliably. These results demonstrate that a very simple measure of ratios of leaf-to-root surface areas in Vallisneria may provide a rapid, sensitive, convenient and inexpensive metric of site quality from the perspective of macrophytes and organochlorine contamination. This could be used to prioritize sites for remedial action, and could confirm environmental improvement following remediation.
Lesley Lovettdoust - One of the best experts on this subject based on the ideXlab platform.
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biomonitoring site quality in stressed aquatic ecosystems using Vallisneria Americana
Ecological Applications, 2001Co-Authors: Kelly Potter, Lesley LovettdoustAbstract:Leaf-to-root surface area ratios in Vallisneria Americana have been shown to provide a simple and inexpensive relative measure of sublethal effects of organochlorine contamination. The present study was conducted to determine whether this index of surface area could be used as an effective biomonitor of overall site quality in stressed aquatic ecosystems. The leaf-to-root surface area ratio was determined for samples of V. Americana collected from 225 microsites within 12 Areas of Concern (environmentally contaminated areas designated by the International Joint Commission) throughout the Laurentian Great Lakes of Ontario. Statistical analyses indicate that 77% of the variation in the surface area index could be attributed to differences among microsites, with only 23% of variation occurring among plants within a microsite. A multiple regression equation was developed for predicting the leaf-to-root surface area ratio from several measures of microsite quality. Significant parameters affecting the surface area ratio included plant density, light intensity, and an index of sediment contamination. In contrast, measures of water contamination did not show any correlation with leaf-to-root surface area ratio. These observations support the hypothesis that V. Americana accumulates contaminants primarily from the sediments and that the leaf-to-root surface area ratio can be used to construct contours of point source impact zones in Areas of Concern. The regression model developed here provides a simple, inexpensive means for monitoring overall site quality throughout the Great Lakes.
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seed output and the seed bank in Vallisneria Americana hydrocharitaceae
American Journal of Botany, 1997Co-Authors: Cynthia Lokker, Lesley Lovettdoust, Jon LovettdoustAbstract:Seed banks and sexual reproduction are known to be significant in colonization and re-establishment of some aquatic macrophyte communities. For highly clonal aquatic macrophytes, however, there is a lack of information on seed production and seed fate as compared with annual sexual species. The seed bank for three populations of Vallisneria Americanain the Huron‐Erie corridor of the Great Lakes was sampled and quantified in the spring of 1994, and related to seed production in the previous season at these sites. Seed deposition rates during 1994 were also assessed. Sites varied in the proportion of plants flowering and in their tertiary sex ratios, but did not differ in seed numbers produced per unit area. The size of the seed bank was not significantly related to the previous season’s seed output, and estimates of seed deposition in the following year tended to be approximately tenfold greater than seed densities found in the seed bank. The stages between seed production and subsequent seed germination are generally very dynamic, with dispersal, mortality, and predation as likely regulating factors. The potential for seedling establishment in V. Americana needs to be assessed more fully before the role of seeds in population processes can be determined.
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laboratory assay of sediment phytotoxicity using the macrophyte Vallisneria Americana
Environmental Toxicology and Chemistry, 1997Co-Authors: Maciej Biernacki, Jon Lovettdoust, Lesley LovettdoustAbstract:In contrast to their ecological importance, submersed rooted macrophytes have been overlooked in environmental science. Presently, the array of standard phytotoxic bioassays includes only one free-floating vascular macrophyte (Lemna) and several algal species. A short-term and inexpensive assay was studied for feasibility in evaluating sediment quality. Cloned ramets of the macrophyte Vallisneria Americana were used to test phytotoxicity of sediments collected at different locations in the Detroit River. Ramets were planted in sediment samples and placed in greenhouse aquaria. After a week of exposure, ramets of V. Americana were destructively sampled and preserved. The leaf and root surfaces areas were determined, and plant biomass was recorded for each ramet. An index of the leaf-to-root surface area ratio was a reliable predictor of sediment phytotoxicity; the ratio of leaf-to-root mass was also useful but proved less consistent. Ramets grown in sediments that were relatively less contaminated with organic compounds had lower values of the leaf-to-root surface area ratio, while plants grown in more contaminated sediments had greater values. Results of analyses of variance indicated that the index of leaf-to-root surface area ratio responded to sediment quality but was not significantly affected by either variation in plant genotype or interaction between sediment and plant genotype. There was a significant correlation (p < 0.001) between rank-ordered results of the present greenhouse study and results of leaf-to-root surface area ratios for plants previously surveyed in the field.
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temporal biomonitoring using wild celery Vallisneria Americana
Journal of Great Lakes Research, 1997Co-Authors: Maciej Biernacki, Jon Lovettdoust, Lesley LovettdoustAbstract:Abstract This study was carried out to assess the effects of sediment type, local water column, source of plants, and duration of exposure between 1990 and 1994 upon growth, survivorship and reproduction of Vallisneria Americana at two sites in the Huron-Erie corridor of the Great Lakes. The major objective was to determine whether year-to-year variations affect consistency of results using Vallisneria as a biomonitoring tool. Relative annual rankings of results from experimental treatments did not change over a 4-year period. However, most of the absolute measures of plant performance varied significantly between years. Effects on plant growth and development were associated primarily with exposure to water columns, and secondarily to sediments. Measures of plant density, rate of clonal growth, leaf length, number of leaves per m 2 , and plant biomass per m 2 were unusually high in the first year compared with the subsequent 3 years, perhaps due to disturbance associated with set-up of the experiment. Leaf-to-root surface area ratios provided a simple, consistent, and reliable measure of environmental quality. Other measures of plant performance varied significantly from year-to-year and, therefore, are not advised for long-term comparisons. Results of this study indicate that Vallisneria can be an effective temporal biomonitor of environmental quality.
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Vallisneria Americana as a biomonitor of aquatic ecosystems leaf to root surface area ratios and organic contamination in the huron erie corridor
Journal of Great Lakes Research, 1996Co-Authors: Maciej Biernacki, Jon Lovettdoust, Lesley LovettdoustAbstract:Aquatic macrophytes are useful biomonitors of sub-lethal effects of organochlorine contamination. Ramets of Vallisneria Americana were sampled from natural populations at 243 sites in the Huron-Erie corridor in August 1993, and an index of leaf-to-root surface area ratios was determined. Sites were then ranked according to this index. Site rankings based on leaf-to-root surface area ratios were significantly correlated with the ranks of these sites using levels of organochlorine contamination of biota or sediment, reported independently in the published literature. The ratio of leaf-to-root surface areas ranged from 2 to 92, and higher values were found in more polluted sites. At four sites, plants were sampled monthly over one growing season, while at two sites plants were sampled each year for 4 years. The leaf-to-root surface area ratio changed little from year to year. At highly polluted sites there was a progressive increase in ratio over the growing season. Surveyed sites remained in the same relative ranking over the growing season, and a single survey within the same month could compare sites reliably. These results demonstrate that a very simple measure of ratios of leaf-to-root surface areas in Vallisneria may provide a rapid, sensitive, convenient and inexpensive metric of site quality from the perspective of macrophytes and organochlorine contamination. This could be used to prioritize sites for remedial action, and could confirm environmental improvement following remediation.
Maciej Biernacki - One of the best experts on this subject based on the ideXlab platform.
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Vallisneria Americana hydrocharitaceae as a biomonitor of aquatic ecosystems comparison of cloned genotypes
American Journal of Botany, 1997Co-Authors: Maciej Biernacki, Jon LovettdoustAbstract:: We assessed the effects of local environment on survival, growth, and development in six clones (genotypes) of Vallisneria Americana grown at five sites in the Huron-Erie Corridor. Detrimental effects of local environment on plant performance (rate of clonal growth, leaf and root production, surface area of leaves and roots, plant biomass, rate of flowering, and turion production) were correlated with sediment toxicity and levels of organic contamination determined in independent studies, and differed among plant genotypes. All surviving clones used in the study ranked environmental quality of the five sites in the same order. Two genotypes, which were tolerant of contaminants, survived the 2 yr of exposure at all sites, while other nontolerant clones died within the 1st yr of study, at the two most contaminated sites. The leaf-to-root surface area ratio was highly indicative of site quality, and was not affected either by year-to-year variation, or by differences between genotypes. The use of cloned plants in this biomonitoring study reduced variance, and increased precision and accuracy of site assessment compared to biomonitoring with genetically variable plants. Clones of V. Americana tolerant of contaminants were particularly useful in assessing the most contaminated sites. An approach that uses an array of both tolerant and nontolerant clones is recommended.
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laboratory assay of sediment phytotoxicity using the macrophyte Vallisneria Americana
Environmental Toxicology and Chemistry, 1997Co-Authors: Maciej Biernacki, Jon Lovettdoust, Lesley LovettdoustAbstract:In contrast to their ecological importance, submersed rooted macrophytes have been overlooked in environmental science. Presently, the array of standard phytotoxic bioassays includes only one free-floating vascular macrophyte (Lemna) and several algal species. A short-term and inexpensive assay was studied for feasibility in evaluating sediment quality. Cloned ramets of the macrophyte Vallisneria Americana were used to test phytotoxicity of sediments collected at different locations in the Detroit River. Ramets were planted in sediment samples and placed in greenhouse aquaria. After a week of exposure, ramets of V. Americana were destructively sampled and preserved. The leaf and root surfaces areas were determined, and plant biomass was recorded for each ramet. An index of the leaf-to-root surface area ratio was a reliable predictor of sediment phytotoxicity; the ratio of leaf-to-root mass was also useful but proved less consistent. Ramets grown in sediments that were relatively less contaminated with organic compounds had lower values of the leaf-to-root surface area ratio, while plants grown in more contaminated sediments had greater values. Results of analyses of variance indicated that the index of leaf-to-root surface area ratio responded to sediment quality but was not significantly affected by either variation in plant genotype or interaction between sediment and plant genotype. There was a significant correlation (p < 0.001) between rank-ordered results of the present greenhouse study and results of leaf-to-root surface area ratios for plants previously surveyed in the field.
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temporal biomonitoring using wild celery Vallisneria Americana
Journal of Great Lakes Research, 1997Co-Authors: Maciej Biernacki, Jon Lovettdoust, Lesley LovettdoustAbstract:Abstract This study was carried out to assess the effects of sediment type, local water column, source of plants, and duration of exposure between 1990 and 1994 upon growth, survivorship and reproduction of Vallisneria Americana at two sites in the Huron-Erie corridor of the Great Lakes. The major objective was to determine whether year-to-year variations affect consistency of results using Vallisneria as a biomonitoring tool. Relative annual rankings of results from experimental treatments did not change over a 4-year period. However, most of the absolute measures of plant performance varied significantly between years. Effects on plant growth and development were associated primarily with exposure to water columns, and secondarily to sediments. Measures of plant density, rate of clonal growth, leaf length, number of leaves per m 2 , and plant biomass per m 2 were unusually high in the first year compared with the subsequent 3 years, perhaps due to disturbance associated with set-up of the experiment. Leaf-to-root surface area ratios provided a simple, consistent, and reliable measure of environmental quality. Other measures of plant performance varied significantly from year-to-year and, therefore, are not advised for long-term comparisons. Results of this study indicate that Vallisneria can be an effective temporal biomonitor of environmental quality.
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Vallisneria Americana as a biomonitor of aquatic ecosystems leaf to root surface area ratios and organic contamination in the huron erie corridor
Journal of Great Lakes Research, 1996Co-Authors: Maciej Biernacki, Jon Lovettdoust, Lesley LovettdoustAbstract:Aquatic macrophytes are useful biomonitors of sub-lethal effects of organochlorine contamination. Ramets of Vallisneria Americana were sampled from natural populations at 243 sites in the Huron-Erie corridor in August 1993, and an index of leaf-to-root surface area ratios was determined. Sites were then ranked according to this index. Site rankings based on leaf-to-root surface area ratios were significantly correlated with the ranks of these sites using levels of organochlorine contamination of biota or sediment, reported independently in the published literature. The ratio of leaf-to-root surface areas ranged from 2 to 92, and higher values were found in more polluted sites. At four sites, plants were sampled monthly over one growing season, while at two sites plants were sampled each year for 4 years. The leaf-to-root surface area ratio changed little from year to year. At highly polluted sites there was a progressive increase in ratio over the growing season. Surveyed sites remained in the same relative ranking over the growing season, and a single survey within the same month could compare sites reliably. These results demonstrate that a very simple measure of ratios of leaf-to-root surface areas in Vallisneria may provide a rapid, sensitive, convenient and inexpensive metric of site quality from the perspective of macrophytes and organochlorine contamination. This could be used to prioritize sites for remedial action, and could confirm environmental improvement following remediation.
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effects of trichlorethylene plant sex and site of origin on modular demography in Vallisneria Americana
Journal of Applied Ecology, 1995Co-Authors: Maciej Biernacki, Jon Lovett Doust, Lesley Lovett DoustAbstract:Summary 1. The demographic effects of an organochlorine contaminant on the dioecious aquatic macrophyte Vallisneria Americana are reported. Plants were sampled from two natural populations in the Huron-Erie corridor of the Great Lakes Basin, and placed in experimental treatments of high (396 mg per litre), medium (132 mg per litre), low (66 mg per litre) and zero concentrations of trichloroethylene (TCE). Plant responses were determined in terms of genet mortality (i.e. death of the entire genetic individual), ramet production (clonal growth) and mortality, leaf birth- and death rates, leaf area and sexual reproduction. 2. TCE in the water caused significant ramet and genet mortality, and reduced the growth of surviving plants. Control plants produced significantly more leaves than contaminated plants. Contaminant-exposed plants continued producing their leaves for 4-6 weeks longer than controls, and showed greater rates of leaf death. The total leaf area of genets exposed to TCE was significantly lower than that of unexposed plants. TCE was associated with a significant decrease in flower production. 3. The concentration of TCE was determined in plant tissues, water and sediment. Levels of TCE were greatest in the sediment, and sediment originating from each site adsorbed TCE to differing degrees. TCE was more concentrated in the underground storage tissues (roots and turions) than it was in leaves. Root and turion tissues of plants from one site contained significantly less TCE than those of plants from the other site, despite an identical concentration of TCE in the water; differences may have been due to contrasting sediment affinities for TCE, and/or different rates of TCE accumulation by the plants from each site. 4. TCE was bioaccumulated, particularly in roots. This appeared to be attributable to the fact that TCE accumulated, in the first instance, in sediments. The logIo of TCE concentrations in sediment were linearly correlated with TCE concentrations in roots, suggesting that TCE uptake is through the root system rather than the leaves, and that uptake is driven by the concentration gradient between sediment and plant. 5. Plants that survived the TCE treatment appeared to be resistant to the chemical; they were as likely to flower as surviving untreated plants. Males were more likely than females to survive TCE treatment. 6. It is concluded that modular demography can be used to characterize the performance of plants that are stressed by exposure to various concentrations of the organochlorine solvent trichloroethylene, and that plants from different sites differ in their ability to survive contaminant stress.
Thomas C Michot - One of the best experts on this subject based on the ideXlab platform.
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effect of nutrients and salinity pulses on biomass and growth of Vallisneria Americana in lower st johns river fl usa
Royal Society Open Science, 2015Co-Authors: Ronald G Boustany, Thomas C Michot, Rebecca F MossAbstract:We determined the interactive effects of nutrient loading and salinity pulsing on Vallisneria Americana Michx., the dominant submerged aquatic vegetation species in the lower St Johns River (LSJR),...
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effects of nutrient pre exposure on atrazine toxicity to Vallisneria Americana michx wild celery
Archives of Environmental Contamination and Toxicology, 2010Co-Authors: Darrin D Dantin, Ronald G Boustany, Rebecca F Moss, Michael A Lewis, Stephen J Jordan, Thomas C MichotAbstract:Accelerated eutrophication is common to many freshwater and marine environments and often co-occurs with the presence of anthropogenic chemicals. However, the toxic effects of common chemical stressors such as herbicides in the presence of elevated nutrients are not well understood for most aquatic flora, particularly vascular species. To provide insight, field-collected Vallisneria Americana Michx. (wild celery) were sequentially exposed to three nutrient concentrations for 3 months and then to nominal 11 and 110 μg L−1 atrazine for 96 h. Nutrient concentrations (combined NH4+, NO2−, NO3−, PO4−) were based on ambient concentrations in the St. Johns River (FL) and ranged from 0.013 to 0.668 mg L−1. Nutrient pretreatment potentiated the toxicity of atrazine as determined by chlorophyll fluorescence activity. Electron transport rates (ETR) were significantly less (48–59%) for plants pretreated with low and ambient nutrient levels in the presence of an average of 107.5–128.1 μg L−1 atrazine. Significant ETR reductions were also observed for plants exposed to an average of 11.4 μg L−1 atrazine after exposure to nutrients three times the ambient concentration in the St. Johns River. The results indicate the importance of considering the presence of nutrients in chemical hazard assessments, particularly for phytotoxicants and nontarget vascular plants.
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effects of salinity and light on biomass and growth of Vallisneria Americana from lower st johns river fl usa
Wetlands Ecology and Management, 2010Co-Authors: Ronald G Boustany, Thomas C Michot, Rebecca F MossAbstract:A mesocosm study was conducted to determine the effects of variable salinity and light on Vallisneria Americana Michx. (wild celery) and associated algal community components in the lower St. Johns River, Florida. Fifteen centimeter diameter intact plant plugs were collected from the LSJR in March 2001 and transported to mesocosm facilities in Lafayette, Louisiana. A factorial experimental design was used consisting of three salinity levels (1, 8, and 18 ppt), three light levels (0, 50, and 90% shading), and three replicate mesocosms of each for a total of 27 mesocosms. The experiment consisted of a 4-week acclimation period followed by a 5-month treatment period. V. Americana responded negatively to increased salinity. Although V. Americana survived 8 ppt salinity, growth was limited. At 18 ppt, almost all V. Americana aboveground biomass had perished within 10 weeks, but when salinity was lowered back to 1 ppt, approximately 20% of the aboveground biomass recovered within the following 10 weeks. At midtreatment harvest, light did not affect V. Americana biomass directly (P = 0.8240), but by final harvest (20 weeks) light affected belowground biomass (P < 0.0014). Both salinity and light affected algal growth. Macroalgae dominated 1 ppt salinity treatments in ambient light, but phytoplankton dominated 8 and 18 ppt salinity treatments in ambient light. Algal communities were greatly inhibited by 90% shading. While salinity directly impacted V. Americana growth and survival, light effects were less direct and involved algal community associations.
