Bioaccumulation and purification of cadmium in Tubifex tubifex

This study compared accumulation of cadmium (Cd) in Tubifex worms (Tubifex tubifex) during exposure to different doses of the metal (0.9 and 2.5 mg/kg) in bottom sediments and in water (0.9 and 2.5 mg/l). Elimination of Cd from these invertebrates by prior exposure was also examined. Cd concentration in water, sediments and worms was analysed by Atomic Absorption Spectroscopy (AAS) method. The results showed higher sensitivity of Tubifex worms to Cd concentration in water (Concentration factors from 16 to 60) than bottom sediments (CF from 0.44 to 0.77). Cd bioaccumulation in worms was positively correlated with its dose and exposure duration (0.88 to 0.94). The highest level of Cd in worms (150 mg/kg) was observed after two days of exposure in water to 2.5 mg Cd/L. The results of purification that was studied the first time after the previous exposure to Cd showed that Tubifex tubifex rapidly reduced Cd concentration (from 28.5 to 0.13 mg/kg) in 3 days after exposure cessation. The results indicate that it is possible to purify Tubifex worms taken from a population existing in contaminated environment to obtain safe food for aquarium fish. Additionally, Tubifex worms can be considered as an ideal cumulative bioindicator of Cd in the water environment.