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Mesotrophic Lake (mesotrophic + lake)

Distribution by Scientific Domains

Life Sciences	66%

Selected Abstracts

Population Density of the Crayfish, Orconectes limosus, in Relation to Fish and Macroinvertebrate Densities in a Small Mesotrophic Lake , Implications for the Lake's Food Web

INTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 5-6 2005
Susanne S. Haertel-Borer
Abstract The population density of Orconectes limosus in a mesotrophic lake was assessed in the context of fish and macroinvertebrate biomasses, and crayfish consumption by fish. The average O.limosus (,6 cm total length) abundance and biomass in the littoral zone was 2200 ind ha,1 and 32.2 kg ha1, respectively. O.limosus biomass accounted for a large percentage (49%) of the lake's macroinvertebrate biomass. O.limosus was equal to 35% of the non-predatory fish biomass and to 81% of the predatory fish biomass. O.limosus comprised 15 and 48% of the annual consumption of pike and predatory perch, respectively. Altogether, O.limosus was identified as quantitatively important for the lake's littoral food web, and might also subsidize the pelagic food web. This strengthens the need for an integrated view on lake food webs. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Metagenomic approach studying the taxonomic and functional diversity of the bacterial community in a mesotrophic lake (Lac du Bourget , France)

ENVIRONMENTAL MICROBIOLOGY, Issue 9 2009
Didier Debroas
Summary The main goals of this work were to identify the metabolic pathways of the bacterial community in a lacustrine ecosystem and to establish links between taxonomic composition and the relative abundances of these metabolic pathways. For this purpose, we analysed a 16S rRNA gene library obtained by gene amplification together with a sequence library of both insert ends on c. 7700 fosmids. Whatever the library used, Actinobacteria was the most abundant bacterial group, followed by Proteobacteria and Bacteroidetes. Specific aquatic clades such as acI and acIV (Actinobacteria) or LD12 and GOBB-C201 (Alphaproteobacteria) were found in both libraries. From comparative analysis of metagenomic libraries, the metagenome of this lake was characterized by overrepresentation of genes involved in the degradation of xenobiotics mainly associated with Alphaproteobacteria. Actinobacteria were mainly related to metabolic pathways involved in nucleotide metabolism, cofactors, vitamins, energy, replication and repair. Betaproteobacteria appeared to be characterized by the presence of numerous genes implicated in environmental information processing (membrane transport and signal transduction) whereas glycan and carbohydrate metabolism pathways were overrepresented in Bacteroidetes. These results prompted us to propose hypotheses on the ecological role of these bacterial classes in lacustrine ecosystems. [source]

Population Density of the Crayfish, Orconectes limosus, in Relation to Fish and Macroinvertebrate Densities in a Small Mesotrophic Lake , Implications for the Lake's Food Web

Biotic and abiotic influences on the recruitment of male perch in Windermere, U.K.

JOURNAL OF FISH BIOLOGY, Issue 6 2004
C. G. M. Paxton
Perch Perca fluviatilis recruitment (based on the catch per unit effort, CPUE, of 2 or 3 year male perch) varied greatly from 1941 to 1995 in Windermere, U.K., with year class strengths strongly synchronous between the two basins of this temperate, mesotrophic lake. Statistically significant modified Ricker (Saila-Lorda) stock-recruitment curves could be fitted to data from three of four sampling sites, while the presence of widespread disease and late summer water temperature were also important explanatory variables. Multiple-regression analyses revealed no influences of pike Esox lucius recruitment, zooplankton abundance, or the climatic influences (i.e. North Atlantic Oscillation and displacement of the summer position of the Gulf Stream) on perch recruitment over and above associated influences from temperature. Fitted models realistically explained up to c. 60% of the observed variation in perch recruitment. [source]

Effects of temperature on isotopic enrichment in Daphnia magna: implications for aquatic food-web studies

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 14 2003
M. Power
Laboratory experiments were conducted with Daphnia magna and Hyalella sp. grown on a single food source of known isotopic composition at a range of temperatures spanning the physiological optima for each species. Daphnia raised at 26.5°C were enriched in ,13C and ,15N by 3.1 and 2.8,, respectively, relative to diet. Daphnia raised at 12.8°C were enriched 1.7 and 5.0, in ,13C and ,15N, respectively. Results imply a significant negative relationship between the ,13C and ,15N of primary consumers when a temperature gradient exists. Similar responses were observed for Hyalella. Results indicate a general increase in ,13C enrichment and decrease in ,15N enrichment as temperature rises. Deviations from the commonly applied isotopic enrichment values used in aquatic ecology were attributed to changes in temperature-mediated physiological rates. Field data from a variety of sources also showed a general trend toward ,13C enrichment with increasing temperature in marine and lacustrine zooplankton. Multivariate regression models demonstrated that, in oligotrophic and mesotrophic lakes, zooplankton ,13C was related to lake-specific POM ,13C, lake surface temperature and latitude. Temperature-dependent isotopic separation (enrichment) between predator and prey should be taken into consideration when interpreting the significance of isotopic differences within and among aquatic organisms and ecosystems, and when assigning organisms to food-web positions on the basis of observed isotope values. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Lake habitat suitability for the rare European macrophyte Najas flexilis (Willd.) Rostk.

AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 3 2005
& Schmidt
Abstract 1.Najas flexilis (Willd.) Rostk. & Schmidt is a submerged annual macrophyte, rare in Europe, which is protected under the EC Habitats Directive. 2.N. flexilis grows in deep, often coloured or turbid water in mesotrophic lakes. Because of this habitat preference it is difficult to locate and assess the ecological state of populations of the species for conservation monitoring purposes. 3.A method is described based on plant community information that can be used to determine the baseline probability that conditions in a lake are suitable for supporting N. flexilis growth. This can be applied to conservation management decisions, such as whether a detailed underwater survey is justified for monitoring the integrity of existing populations of N. flexilis, or whether the lake may be a suitable site for introduction, or reintroduction, of populations of the plant. 4.Two methods of plant community description are compared: a quantitative micro-habitat scale approach and a whole-lake-scale qualitative approach. Plant community data collected using each method were grouped using TWINSPAN, and environmental descriptors of the sites comprising each plant community group were compared statistically. 5.Micro-habitat-scale community groups differed significantly only in the light extinction coefficient, indicating the zone within the lake in which N. flexilis occurred. 6.The whole-lake-scale community groups differed in a number of environmental variables indicative of eutrophication and acidification, two major environmental threats to N. flexilis survival. 7.This study suggests that a lake-scale qualitative plant community description would be a better indicator of site suitability for N. flexilis growth than a quantitative micro-habitat plant community description. This is because the whole-lake-scale approach could detect a difference in the environmental factors that affect N. flexilis growth, which the micro-habitat scale approach could not. Copyright © 2005 John Wiley & Sons, Ltd. [source]