Determination of the toxicity of cadmium in three populations of Littorina littorea taken from a pollution and salinity gradient in the Scheldt estuary (Mollusca: Gastropoda)
Kwamla Atupra, D. (2001). Determination of the toxicity of cadmium in three populations of Littorina littorea taken from a pollution and salinity gradient in the Scheldt estuary (Mollusca: Gastropoda). MSc Thesis. Vrije Universiteit Brussel: Brussel. 88 pp.
In this study, we determined the toxicity of cadmium in three populations of Littorina littorea, taken from a pollution and salinity gradient in the Scheldt estuary .Lethal toxicity that kills Littorina littorea at a given time, (e.g. LC5, LC50, and LC95) were calculated after a toxicity range finding test using EPA probit model. For instance the LC5o at 96 hours was found to be 476.48µM, with the lower and upper confident interval of 320.95µM -730.56 µM. Subsequently L. littorea from different populations of Weskapelle, Ellewoutsdijk and Hansweert were exposed to different concentration regimes of Cadmium chloride (CdCl2) of lOµM -320µM. Then finally an experiment in which they were kept in varying salinity ranging from 15‰--35‰, but constant total cadmium concentration of 10µM. The mortality and tissue level of Cd in L. littorea increased in the order: Weskapele < Ellewoutsdijk< Hansweert. Then in the salinity-cadmium experiment we obtained higher mortality in the lower salinity and the order of the mortality is from the marine population of Weskapelle to the relatively fresh water population of Hansweert. This we attribute to the "salinity factor" with decreased amount of free Cd2+ due to the higher Cd complexation in the higher salinity. Secondly, within each salinity the observed difference in mortality and metal body burden we attribute to the inherent adaptation and also to the already higher levels of metals (body burden) which increase from the marine population of Weskapelle to the relatively fresh water population of Hansweert. Within each salinity also irrespective of the population higher levels of Cd and Cu were accumulated but not for Na, K, Mg, and Zn probably due probably to their osmoregulatory functions they were not bioaccumulated.
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