Toxicity assessment of cadmium chloride on planktonic copepods Centropages ponticus using biochemical markers

Pollution of the aquatic environment by heavy metals has become a worldwide problem. Most heavy metals exhibit toxic waste on aquatic organisms. Cadmium (Cd) is a highly toxic metal which affects aquatic organisms acutely and chronically. Planktonic calanoid copepods are the secondary dominant producers of pelagic ecosystems and play a considerable role in the transfer of energy and organic matter from primary producers to higher trophic levels. We investigated the effect of cadmium chloride on biochemical responses of the planktonic calanoid copepods Centropages ponticus which is a key species in the Mediterranean Sea. The response of copepods to cadmium chloride was examined under laboratory-controlled conditions during a 72-h exposure. Catalase (CAT), Glutathion Reductase (GR), Glutathione Peroxidase (GPx), Glutathione-S-Transferase (GST) and Acetylcholinesterase (AChE) were analyzed for cadmium chloride treatments (0, 0.2 and 0.4 μg/L) after 24, 48 and 72 h. Additionally, the thiobarbituric reactive species assay was used to evaluate lipid peroxidation (LPO) level of the copepod. In this study, it is observed that contents of protein increased gradually with an increase in concentrations of metals and exposure time. Our findings showed that cadmium chloride directly influenced malondialdehyde (MDA) levels in the treated copepods hinting that the copepods had suffered from oxidative damage. During exposure, the Cd treatments significantly influenced the biochemical markers (CAT, GR, GPx, GST and AChE). Thus, Centropages ponticus could be used as a suitable bioindicator of exposure to Cd using biochemicals markers. Keywords: Biomarker, Planktonic copepod, Cadmium, Centropages ponticu

Antioxidant activity of Aplysia depilans ink colleted from Bizerte Channel (NE Tunisia)

The ink secretion of molluscan species was identified as one of the novel sources of bioactive compounds. The present study aims to evaluate the in vitro antioxidant activity of Aplysia depilans ink extract. The antioxidant activity of ink extract were evaluated using 2,2- diphenyl-1-picrylhydrazyl (DPPH) scavenging activity, Hydroxyl radical scavenging activity, Ferric ion reducing power (FRP) and Ferrous ion chelating (FIC) activity. The results from the present work revealed the strongest antioxidant activity of Aplysia depilans ink. The electrophoretic profile showed band with molecular weight of 60 kDa. The highest antioxidant activity in ink extract probably may be due to the presence of this protein with lower moleculair weight

Zn(II), Pb(II) and Cd(II) levels in livers and muscles of wild duck (Anas platyrhynchos) hunting in El Melah Lagoon (NE Tunisia)

We investigated the levels of Zn(II], Pb(II] and Cd(II] in livers and muscles of the wild duck (Anas platyrhynchos) hunting in El Melah lagoon in northeastern Tunisia from December 2010. Analysis of variance shows that no significant differences in metals levels were found between samples, but it should be pointed out that the number of samples was small. HSD Tukey test show that the amount of Cd(II], Zn(II] and Pb(II] in the levers was higher than in the muscles. The results obtained suggest the importance of wild ducks as bioindicators of heavy metal pollution

Environmental controlling factors of copepod communities in the Gulf of Tunis (south western Mediterranean Sea)

The copepod community structure and the distribution of the main groups of zooplankton were studied along an inshore-offshore gradient in the Gulf of Tunis during the rainy and dry seasons of 2007-2008. Hydrological parameters were also measured to assess the potential role of abiotic and biotic factors in the distribution of copepod species. The copepod community in the Gulf of Tunis comprises 86 species dominated by Paracalanus parvus, Clausocalanus lividus, Centropages kroyeri and Acartia clausi. Time had a greater influence than space (horizontal and vertical gradients) in shaping the copepod community structure with a significant influence of the seasons; winter (cold and rainy) resulted in hydrological conditions that were strongly different from those observed in summer (warm and dry). These hydrological differences were concomitant with changes in the community structure, with a high copepod diversity observed in winter while the summer period was characterized by a low specific richness and the dominance of a few species, Centropages kroyeri and Paracalanus parvus along the inshore-offshore gradient and Paracalanus aculeatus along the vertical. Canonical correspondence analysis showed that temperature, salinity and to a lesser extent chlorophyll a were the most important environmental factors structuring the copepod community. Interestingly, temperature and salinity showed a negative significant correlation with copepod specific richness. Competition with grazers (cladoceran) as well as top down control by predators (chaetognaths and siphonophors) were also identified as key factors for the copepod community structure