This paper describes two approaches to evaluate the use of fish macroparasites as bioindicators of heavy metal pollution at selected river stretches in Austria. Firstly changes in the diversity and richness of endoparasites of the cyprinid barbel, Barbrus barbuls (L.), were tested in relation to heavy metal contents in the aquatic system. Secondly, the bioaccumulation potential of cadmium, lead and zinc was assessed in the acanthocephalan, Pomphorhynchus laevis (Miller, 1776), and compared with that in the muscle, liver and intestine of its barbel host. The present results indicated that in order to validate the role of parasite community patterns related to heavy metal pollution, more investigations on food web dynamics, interelationships between parasites and the presence/absence of intermediate hosts will be essential. Heavy metal concentrations differed significantly between the organs of barbel and P. laevis (P=0.001) with levels up to 2860 fold in the parasite. The high level of heavy metal accumulation in P. laevis compared with that in its barbel host, suggests that despite variability in the parasite infrapopulation, host mobility and feeding behaviour, P. laevis is a most sensitive indicator of heavy metals in aquatic ecosystems.
This study analyses interspecific differences in anuran tadpole swimming behaviour that could influence vulnerability and therefore prey selection by dragonfly nymphs (Aeshna cyanea). Laboratory experiments showed that Bufo bufo tadpoles were almost continually and slowly in motion, which makes them easy prey for the dragonflies. Hyla arborea tadpoles were also very active and slow in swimming; in contrast to Bufo, however, they showed effective predator avoidance strategies (different habitat preferences, high evasiveness). The predation risk of Rana dalmatina larvae was low because the tadpoles were immobile and benthic, rare movements were made with high speeds. Bombina bombina is intermediate in swimming activity, velocity, and vulnerability.
Dragonflies are reliable indicators of the ecological quality of land -water ecotones, habitat heterogeneity and the hydrological dynamics of water bodies. In recent years, surveys of dragonfly communities have become a powerful tool for the ecological assessment of floodplain areas. The goal of this paper is to present a new approach towards assessing the ecological integrity of river-floodplain systems by analysing resident breeding dragonfly species. The methodology is based on experiences with existing approaches using macroinvertebrates as bioindicators, in particular, calculations of saprobic indices, longitudinal zonation and functional feeding group patterns. In addition to the total number of species and the number of sensitive species, the 'Odonate Habitat Index' (OHI) is a key element of the assessment method. It indicates characteristic features of a river -floodplain system, such as connectivity aspects, flow dynamics and terrestrialization processes. The OHI is calculated from the species-specific habitat values (expressing habitat preferences), abundances and the species-specific indication weight, which distinguishes eurytopic from stenotopic species. The comparison of the status quo with a reference condition allows an assessment of individual water bodies and/or of a whole area in a five-tiered classification scheme. The approach presented may also be used for the evaluation of restoration measures (e.g. reconnection of side arms) and for the definition of management objectives. Apart from the methodological framework, the results of a first application of this approach are presented in the paper as well. The study areas were selected floodplain systems of the Austrian section of the Danube and man-made inshore structures of the impounded Danube section in Vienna. Copyright
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