African Journal of Aquatic Science

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A chronic toxicity test protocol using Caridina nilotica (Decapoda: Atyidae) and the generation of salinity toxicity data

AR Slaughter, CG Palmer, WJ Muller


Salinization of freshwater resources is an increasing global problem, yet there is a paucity of chronic salinity tolerance data linked to very few chronic toxicity test protocols. This research aimed to generate a chronic toxicity test protocol and protective salinity tolerance data for the indigenous South African freshwater shrimp Caridina nilotica. In addition, the theory that LC5s (concentration causing 5% lethality) are indicative of No Observed Effect Concentrations (NOECs) was tested. NaCl and Na2SO4 were used as toxicants as they are indicative of natural and industrial salinization, respectively. NOEC values of 1.9 g l–1 were calculated for both salts. Within the chronic toxicity tests, LC5s that were calculated using regression methods approximated the calculated NOEC values for both salts. Chronic NOECs calculated here are lower, by a factor of 3, than the acute LC50s calculated for the same species and salts. Although evidence exists to suggest that C. nilotica is generally sensitive to toxicants, it was found to be not particularly sensitive to salinity. However, the species was found to be a good chronic toxicity test organism for partial life-cycle toxicity tests where growth was measured as the test endpoint, and may yield valuable chronic toxicity data for other toxicants.

Keywords: freshwater shrimp, toxicity tests, chronic response, growth rate, mortality, reproduction

African Journal of Aquatic Science 2008, 33(1): 37–44
AJOL African Journals Online