Gudrun De Boeck

Contamination by heavy metals in aquatic environments is a serious concern due to increasing human activities over the last decades. Moreover, productive areas such as estuaries have even been more affected because of the complex interaction between fluvial and marine processes, creating a stressful environment with gradients of salinity and other important parameters which can intensify negative effects of pollutants on biota such as euryhaline fish. (Oliva et al., 2012; Mieiro et al 2012). European sea bass (Dicentrarchus labrax l.) is a euryhaline species able to withstand a large variation in salinity and is considered as a bioindicador due to both economic and ecological importance (Joseph., et al 2011; Loizeau, 2001). Copper as essential micronutrient has important roles in cellular, enzymatical and protein mechanisms but is potentially toxic when its concentration increases above a certain threshold (Blanchard & Grosell, 2005; Grosell et al., 2007), and can even be more toxic than cadmium, a non-essential metal (Roméo et al., 2000) which is ubiquitous in environment and one of the most deleterious heavy metal pollutants (Nath et al., 1984 cited by Loaiza, 2011). Therefore, the effect of salinity on the acute toxicity of copper and cadmium in European sea bass D. labrax l. was examined to determine 96h-LC50 values (the lethal concentration where 50% of the population dies) at different exposure concentration of both metals (at 0 to 5100 μgCu L-1 and at 0 to 20000 μgCd L-1) over a broad salinity range (1, 2.5, 5, 10, 20, 28, 35‰) in juvenile sea bass during a period of 10 days. The results showed an important influence of the salinity in the toxicity in both elements, where for Cu mortality first decreased with increasing salinity but increased again at higher salinities and for Cd, mortality decreased continuously with increasing salinity, to a point where no reliable LC50 could be determined at the 2 highest salinities. In addition, it was observed that the individuals were affected in different ways. For instance Cu exposed fish at low salinity showed opened gills at die-off. Copper is readily taken up by the gill, where it inhibits the action of Na+/K+ adenosine triphosphatase, resulting in an osmoregulatory disturbance as Na+ is lost to the dilute external environment (Blanchard et al. 2006). In conclusion, the salinity influences the toxicity differently for Cu and Cd. This not only occurs due to the fact that salinity plays an important role in the speciation of pollutants and competition by cations in uptake processes, but as can be clearly seen in the case of Cu, also by the physiology of the fish that responds to the changes in the environment. Further research on the relationship between bio-accumulation of the metals and the mortality at different salinities is planned.

The present study was conducted to link the heavy metal load in three species of mussels (Perna perna, Mytella falcata and Mytella guyanensis) from the estuaries and bays around Vitória island, south-east of Brazil, with the salinity gradient and the heavy metal levels in the abiotic environment (including water, suspended particulate matter (SPM) and sediment). Primarily based on the salinity gradient, a total of 26 sites around Vitória Island were selected for sampling of water, SPM, sediments and organisms. Besides tissue metal levels, the condition index and energy stores (glycogen, lipid and protein) were quantified as an indicator of fitness in response to metal pollution. Dissolved metals in water indicate that Cd and Mn content was higher along Espírito Santo Bay, while Al, Co, Cu, Cr and Fe were elevated in the sites with low salinity such as river mouths, estuarine and sewage canals. Likewise, suspended matter sampled from low salinity sites showed a higher heavy metal loa...

The aim of this study was to investigate metal accumulation and detoxification processes in cattle from polluted and unpolluted areas. Therefore dairy cows from farms and free ranging Galloway cows from nature reserves were used as study animals. The concentrations of Ag, Cd, Pb, Al, Cr, Mn, Fe, Co, Ni, Cu, Zn and As were determined in muscle, kidney, liver and lungs of cattle from polluted and reference areas in Belgium. In kidney and liver also the metallothionein concentrations were measured. For Ag, Mn, Co, Cu, Zn and As the concentrations in the different tissues were significantly higher in the sampled Galloways than in the sampled dairy cows. On the other hand Cd and Pb were significantly higher in tissues of both cattle breeds from polluted sites. Cadmium seemed to be the most important metal for metallothionein induction in kidneys whereas Zn seemed to be the most important metal for the induction of metallothionein in the liver. This study also suggested that only for Mn a...

The present study aimed to determine whether gill macro- and microstructure show compensatory responses in three freshwater fish differing in their sensitivity to high environmental ammonia (HEA). The highly ammonia-sensitive salmonid Oncorhynchus mykiss (rainbow trout), the less ammonia-sensitive cyprinid Cyprinus carpio (common carp) and the highly ammonia-resistant cyprinid Carassius auratus (goldfish) were used as test species and were exposed for 0 h (control), 3h, 12h, 24h, 48 h, 84 h and 180 h to 1mM ammonia (as NH4HCO3; pH 7.9). In cyprinids, dramatic alterations were initiated quickly evident by thickening of filaments and lamellae, retraction of lamellae, enlargement of interlamellar cell mass (ILCM), and increase in the water-blood diffusion distance; while in trout, these modifications were absent or developed very slowly. These reorganizations may attempt to reduce the surface area presumably protecting against the water borne ammonia; and were more pronounced in goldfi...

In the present study, the combined effects of hypoxia and nutritional status were examined in common carp (Cyprinus carpio), a relatively hypoxia tolerant cyprinid. Fish were either fed or fasted and were exposed to hypoxia (1.5-1.8mg O2L(-1)) at or slightly above their critical oxygen concentration during 1, 3 or 7days followed by a 7day recovery period. Ventilation initially increased during hypoxia, but fasted fish had lower ventilation frequencies than fed fish. In fed fish, ventilation returned to control levels during hypoxia, while in fasted fish recovery only occurred after reoxygenation. Due to this, C. carpio managed, at least in part, to maintain aerobic metabolism during hypoxia: muscle and plasma lactate levels remained relatively stable although they tended to be higher in fed fish (despite higher ventilation rates). However, during recovery, compensatory responses differed greatly between both feeding regimes: plasma lactate in fed fish increased with a simultaneous b...