The objectives of this study were to compare the sensitivity of three freshwater macroinvertebrate shredder species (Atyaephyra desmarestii, Echinogammarus meridionalis and Schizopelex festiva) to acute stress induced by eucalyptus leaf extracts and copper, independently and in mixtures, and the ability of temperature to influence the chemicals’ toxicity. Laboratory bioassays based on mortality with single substances and mixtures were carried out with the three species at 10 and 20°C. After 96 h of exposure, S. festiva, A. desmarestii and E. meridionalis were found to have differences of sensitivity to copper, eucalyptus leaf extracts and their mixtures, with S. festiva being the least sensitive species at both 10 and 20°C. The relative sensitivity of A. desmarestii and E. meridionalis to chemical exposure seems to be chemical and temperature dependent. Overall, these findings suggest that chemical stress may modulate the biodiversity of stream shredders communities due to differential sensitivity of individual species to environmental contaminants, and that temperature may influence the process. Thus, more knowledge on the combined effects of multi-stressors is needed, particularly on temperature and chemicals’ interactions and on the molecular mechanisms underlying the responses observed at individual level.

The Asian clam Corbicula fluminea is one of the most invasive species in freshwater aquatic ecosystems. The rapid growth, earlier sexual maturity, short life span, high fecundity and its association with human activities makes C. fluminea a non-indigenous invasive species likely to colonize new environments. This species, originally distributed in Asiatic ecosystems, is now a common inhabitant of American and European freshwater habitats. The present paper reviews the information related to the life cycle, ecology and potential ecological and economic impacts caused by C. fluminea in the invaded habitats. Furthermore, this paper also proposed future works that may be implemented in order to increase our general knowledge about the ecology of this bivalve.

This study evaluated the status of the Asian clam Corbicula fluminea (Müller, 1774) in the River Lima estuary (Portugal), which it first invaded in 2002. During the summers of 2004 and 2005, spatial and temporal variations in the abundance, biomass and population structure of C. fluminea were investigated in this estuary. This species was present in a limited intertidal area of the estuary and was rarely found in the subtidal zone. Its abundance and biomass were considerably lower than those found in other estuarine systems. Based on these studies it appears that salinity fluctuations and possibly other factors such as nutrients and environmental contaminants are keeping this invasive species from reaching its full potential. Given the lower abundance and biomass recorded and the restrict distribution of the species in this estuary, the eradication of this nonindigenous invasive species is still possible. The findings of this study may be useful for the management of this species not only in the River Lima estuary but also in other locations it may invade.

Ten species of molluscs were identified in the freshwater tidal area of the River Minho estuary. Species richness per site ranged from 1 to 9. Abundance ranged from 230 to 4130 individuals per m², with an average of 1412 individuals per m2. Corbicula fluminea(Müller, 1774) presented the highest density, corresponding to 88.7 % of the total specimens gathered, followed by Pisidium amnicum (Müller, 1774) with 5.8 %. Biomass ranged from 17.0 to 249.6 g AFDW m-2, with an average of 99.8 g AFDW m-2. C. fluminea was the species dominating the total biomass (95.4 %), followed by Bithynia tentaculata (Linnaeus, 1758) with 1.6 %. A multivariate analysis revealed a community with two distinct groups : one group almost or exclusively represented by C. fluminea, and another group with a more diverse assemblage.