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  • 1
    ISSN: 1573-5117
    Keywords: Coenagrionidae ; life history ; lowland river ; urbanpollution ; Ischnura ; Cercion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The species composition of the damselfly assemblage and the life history patterns of two Coenagrionidae (Ischnura elegans and Cercion lindeni) were investigated along the urban tract of a river characterized by increasing organic pollution. The assemblage was dominated by generalist species, usually recorded in lentic habitats, rather than by typical riverine species and the proportion of the latter decrease at the most polluted sites. At the end of Winter, the mean size and in star distribution were different between the sampling sites showing that the life history of both species examined were influenced by a degradation of the environmental quality. A longer reproductive period, absence of diapause, and tolerance of low oxygen concentration appear to be key factors that allow generalist species I. elegans and C. lindeni to predominate at the polluted sites.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-5117
    Keywords: Biomonitoring ; macrobenthos ; chronological clustering ; artificial substrates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The lowland stretches of rivers are usually the ones where a macroinvertebrate species collection is more difficult to obtain because of the depth and turbidity of the water. Since the choice of the index and of the specific sampling technique is critical for the final result, there is a strong interest into setting up reliable methods for assessing the biological water quality. The aim of this paper is to elucidate the performances of four biotic indices and the influence of four sampling methods on the water quality assessment of a deep and turbid stretch of a river. We collected macroinvertebrates seasonally at 10 sampling sites along the final stretch of the Tiber River using four sampling methods (including hand net, wood and plastic artificial substrates). At the same time, chemical, physical, and bacteriological variables were recorded monthly along the same river stretch. Considering those variables, sampling sites were grouped into three clusters with different water quality, using the chronological clustering method. The same result was obtained from macroinvertebrate data using the same method. We then examined the ability of four biotic indices widely used in Italy to discriminate between the three clusters. The indices are: BMWP' (British Monitoring Working Party, modified for Spain), ASPT' (Average Score Per Taxon, modified for Spain), EBI (Extended Biotic Index) and IBE (Indice Biotico Esteso). BMWP' and ASPT' showed the best results. BMWP' and ASPT' scores – but not those of EBI and IBE – were sensitive to the different sampling methods utilised. We concluded that in this type of river stretch, BMWP' and ASPT' could be more useful than EBI and IBE although the relative efficiency of the chosen sampling method should be taken into account.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-5117
    Keywords: biomass size spectra ; area–weight relationships
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The absence of a rapid and inexpensive method for estimating macroinvertebrate individual biomass is a limit to the study of freshwater communities, given that traditional methods are time- and money-consuming. We propose an inexpensive method to quickly estimate individual biomass from video-recorded images of pond macroinvertebrates. We used a software that automatically measures several body dimensions (area, perimeter, minor and major axes) on each individual and linear regression to relate these body dimensions to dry weight. Area was found to be the best predictor of dry weight. The method allows individual measures of macroinvertebrates at a reasonable speed and accuracy, and may be useful for biomass size spectra or secondary production studies.
    Type of Medium: Electronic Resource
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  • 4
    Publication Date: 2017-01-31
    Description: Human activities have differentially altered biogeochemical cycling at local, regional and global scales. We propose that a stoichiometric approach, examining the fluxes of multiple elements and the ratio between them, may be a useful tool for better understanding human effects on ecosystem processes and services. The different scale of impacts of the elements carbon, nitrogen and phosphorus and the different nature of their biogeochemical cycles, imply a large variation of their stoichiometric ratios in space and time and thus divergent impacts on biota. In this paper, we examine the effects of anthropogenic perturbations on nutrient ratios in ecosystems in two examples and one case study. Altered stoichiometry in agricultural systems (example 1) can affect not only crop yield and quality but also the interactions between plants and their pollinators, pests and pathogens. Human activities have also altered stoichiometry in coastal ecosystems (example 2). Increased N loading has especially lead to increased N:P and reduced Si:N ratios, with detrimental effects on ecosystem services derived from coastal pelagic food webs, such as fish yield and water quality. The terrestrial–aquatic linkage in stoichiometric alterations is illustrated with a case study, the Mississippi River watershed, where anthropogenic activities have caused stoichiometric changes that have propagated through the watershed into the northern Gulf of Mexico. Coupled with altered stoichiometric nutrient inputs are the inherent differences in variation and sensitivity of different ecosystems to anthropogenic disturbance. Furthermore, the connections among the components of a watershed may result in downstream cascades of disrupted functioning. Applying a multiple element perspective to understanding and addressing societal needs is a new direction for both ecological stoichiometry and sustainability.
    Type: Article , PeerReviewed
    Format: text
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