Comparative sensitivity ofCaridina nilotica, Haplochromis nubilus, Bulinus africanusandBulinus forskaliifrom Lake Victoria, Tanzania to mercury chloride

Lake Victoria has been under increasing threat of mercury pollution derived from artisanal gold mining, where mercury is amalgamated with gold. Despite the fact that mercury and its derivatives can adversely affect the aquatic biota in Lake Victoria, comparative studies to determine the susceptibility of native biota to mercury have seldom been done. This study was done to compare the susceptibility of shrimps (Caridina nilotica), fish Astatotilapia nubia (Boulenger, 1906) or Haplochromis nubilus, and two species of fresh water snails (Bulinus africanus and Bulinus forskalii) to mercury chloride (HgCl2) in water. The results indicated that C. nilotica is the most susceptible to mercury-induced toxicity among the tested organisms with 96 h LC50 of 8 μg/l. The second most susceptible species was B. forskalii which exhibited LC50 of 98 and 68 μg/l after 72 h and 96 h of exposure respectively. Hypochromis nubilus was the least sensitive species to mercury toxicity of the four tested organisms with 96 h LC50 of 162 μg/l. Findings from the present study suggest that C. nilotica is sensitive to mercury chloride and can be used to assess Hg environmental risk in Lake Victoria.