Limnological characteristics and recent ostracods (Crustacea, Ostracoda) of freshwater wetlands in the Parco Oglio Sud (Northern Italy)
ABSTRACT We report the results of a study carried out in 2002 on the main limnological characteristics and on the ostracod communities of 16 wetlands of the Parco Oglio Sud (Northern Italy). Physical and hydrochemical variables were measured and ostracod samples were collected in different seasons (April, June, August, and October). Most of the considered sites were characterised by high concentrations of nitrogenous compounds due to washing out from cultivated areas, intermittent river flooding and internal recycling. Observed differences in macrophyte communities were consistent with trophic status of waters, with pleustonic forms dominating most degraded areas. Both morphology of valves (by scanning electron microscopy) and anatomy of soft parts were analysed for ostracod species identification. Nineteen ostracod species in five families were found. Two species, Candona weltneri and Pseudocandona compressa, are new records for Italy. Cypria ophthalmica was collected from all sampling sites; other relatively common species were Cypridopsis vidua, Cyclocypris ovum, and Candona weltneri. No clear seasonality was observed in community structure; highest species diversity occurred in June in most of the studied wetlands. The maximum number of species per site was seven, and a maximum of six species was found in a single sample. Ostracod occurrence in relation to environmental factors was examined using Canonical correspondence analysis (CCA). Total alkalinity and pH were the most important variables structuring the species assemblages. The ostracod fauna found in this area was compared to the known distribution of recent non-marine ostracods in Italy, and the validity of published checklists is discussed.
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ABSTRACT: The sometimes sharp thermal variations and irregular precipitations and force concentrated over short periods characterize the Mediterranean climate. The structure of the zooplanktonic settlement was analyzed during one year in three Algerian reservoirs (lakes) with different geographical and climatic situation, in relation to abiotic factors (temperature, dissolved oxygen, pH, suspended matter, carbonates, nitrogenized and phosphorated nutritive salts). A canonical correspondence analysis was used to estimate the influence of the abiotic factors on the temporal distribution.The studied lakes are located, on the one hand, in northern Algeria, in a sub-humid area (Lake Boukourdane) and, on the other hand, in the South of the country, in the arid region (Foum El Ghorza and Djorf Torba). Analysis of the environmental parameters indicates that there is a seasonal variation in the three reservoirs. In Lake Foum El Ghorza, the temperature and hydrology variations, linked with the arid climate, affects the concentration of dissolved oxygen, which strongly decreases (1.5 mg/l), involving a pH reduction; suspended matters are sometimes high, coming from the stripped catchment area, causing a turbidity in this not very deep lake. The study of the distribution of the species allowed us to highlight a seasonal temporal variation. Lake Boukourdane, in the sub-humid zone, has an increased specific richness (SR=13). The various species evolve in alternation during the annual cycle. The representative species of this lake is Copidodiaptomus numidicus, characteristic of the rainy and endemic zone of the western Mediterranean; it is dominant (67%) in the spring. The Stenothermal species Diaphanosoma brachyurum, endemic of hot waters, is common to the two lakes; it evolves particularly in the summer (51.3%) at Boukourdane, whereas it is perennial and dominant (55%) in the spring at Djorf Torba. The specific richness is lower in Djorf Torba (SR=7) and in Foum El Ghorza (SR=6). The species collected in these two lakes are common and cosmopolitan, but they are adapted to the extreme conditions of the arid climate. Nevertheless, the species evolving in Lake Foum El Ghorza have undergone a significant decline, which has reduced the number of species and their density in the summer–autumn period. Thus, we can say that in the studied lakes, the hydrological factors and the temperature related to the Mediterranean climate would be two of the principal causes of the temporal distribution of the species. To cite this article: M. Cherbi et al., C. R. Biologies 331 (2008).Comptes Rendus Biologies - C R BIOL. 01/2008; 331(9):692-702.
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ABSTRACT: This paper revises the response of freshwater ostracods to different environmental conditions and anthropogenic impacts, with a worldwide overview of the potential use of these microcrustaceans as bioindicators and several examples of applications in different scenarios. The development of either a single species or an ostracod assemblage is influenced by physical–chemical properties of waters (salinity, temperature, pH, dissolved oxygen), hydraulic conditions, bottom grain sizes or sedimentation rates. In addition to population and community changes, morphological and geochemical changes can also be detected in the ostracod carapace, which serves as a tracer of the water quality. All these features permit to delimit the spatial effects of urban sewages, mining effluents, agricultural wastes, watershed deforestation or road building. These data are the basis for the palaeoenvironmental reconstruction of cores, with an interesting application to archaeology. In addition, favourable results of recently developed bioassays, coupled with an important variability of local assemblages under changing conditions in both waters and sediments, suggest that these microcrustaceans may included between the most promising sentinels groups in freshwater areas. These microcrustaceans show high sensitivity to pesticides, herbicides, heavy metal pollution and oil inputs.International journal of Environmental Science and Technology 03/2013; · 1.79 Impact Factor