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Biotic interactions such as predation may influence the success of invasive alien species (IAS). Although the Asian clam Corbicula fluminea is recognized as one of the most problematic aquatic IAS, few studies have investigated its use as a food resource. In this study, we aimed to investigate (i) the palatability of C. fluminea under natural (Minho River) and laboratory conditions and (ii) if C. fluminea submitted to different conditions (individuals from Lima and Minho Rivers) vary in palatability. Soft tissues from different Corbicula populations, plus soft tissues from a native clam, tuna and Corbicula shell powder were offered to consumers. Field assays were performed seasonally and laboratory assays only in summer; both assays also tested possible differences during distinct periods of the day. Overall, in natural conditions, the treatments containing C. fluminea had a low palatability. In laboratory assays, higher consumption (almost two times) was observed for Cyprinus carpio and Anguilla anguilla. Also, C. fluminea palatability was different between populations, with the treatment Corbicula Lima being more consumed than Corbicula Minho. Despite the low values of consumption in the field, laboratory results suggest that C. fluminea soft tissues can be a food resource to some species. [ABSTRACT FROM AUTHOR]

Forty-nine surface sediment samples from the Minho estuary sector between Tui and Caminha were analyzed for grain-size contents, Al, As, Cr, Cu, Hg, Li, Pb, Sn, and Zn concentrations. Selected heavy metal (Cu, Cr, Hg, and Zn) and metalloid (As and Sn) distributions were normalized against Al and Li with the main goal of compensating for natural grain-size variability and to separate natural from anthropogenic contributions, by using a combination of normalization techniques (definition of regional geochemical baselines (RGB) and determination of enrichment factors (EF)). Lead did not reveal a significant relationship with Al and Li. Aluminum explained more variance than Li for As, Cu, Hg, and Zn. Assuming the general non-impacted metal character of the Minho River estuary sediments, RGBs are defined for differentiating between natural and anthropogenic contributions. Based on RGB defined for each heavy metal/metalloid, the degree of enrichment is estimated through the determination of EF. Despite the relatively low total heavy metal and metalloid concentrations, the defined RGB identifies a set of samples characterized by presenting As, Cu, Cr, Hg, and Zn enrichments relatively to expected natural levels. Mercury is the element showing the highest level of enrichment relative to the baseline values being spread through all the study area. Tin present enrichments relatively to Al and or Li always lower than 1.5 suggesting natural contributions. [ABSTRACT FROM AUTHOR]