Comparative sensitivity of three tropical cladoceran species (Diaphanosoma brachyurum, Ceriodaphnia rigaudii and Moinodaphnia macleayi) to six chemicals.

The toxicities of six chemicals (cadmium chloride, potassium dichromate, sodium dodecyl sulfate, potassium chloride, Tritox X-100 and copper (II) sulphate) was determined for three tropical freshwater cladoceran, Moinodaphnia macleayi, Ceriodaphnia rigaudii and Diaphanosoma brachyurum. The data was subsequently used to compare the relative sensitivity of the three species. Relative sensitivities were determined by comparing the 48-hour LC50 values using an independent t-test and interspecies correlation. Potassium dichromate was the most toxic compound tested, while potassium chloride was the least toxic to all three species. The 48 h LC50 values for D. brachyurum ranged from 0.003 mg/L to 30.4 mg/L; M. macleayi LC50 values ranged from 0.003 mg/L to 30.1 mg/L whereas for C. rigaudii the values ranging between 0.002 mg/L to 21.1 mg/L. The LC50 values for C. rigaudii was significantly less (P < 0.05) than M. macleayi for five of the compounds tested, whereas for D. brachyurum it was significantly (P < 0.05) less than four of the compounds tested. The interspecies correlation also suggested that C. rigaudii and M. macleayi were more similar in sensitivity (R2 = 0.96) to each other than D. brachyurum (R2 = 0.91 with M. macleayi, and R2 = 0.87 with C. rigaudii).