Toxic Effect of Tributyltin (TBT) on Different Green Microalgal Species

Abstract

The toxic affect of tributyltin (TBT) on six species of two different genera of microalgae, namely Chlorella sp. and Scenedesmus sp. was examined. The resistance of the commercially available species and isolates obtained from polluted water in Hong Kong and Wuhan, PRC to TBT were also compared. Chlorella vulgaris and S. dimorphus were commercial species while C. sorokiniana, S. quadricauda, C. miniata, and S. platydiscus were isolates. Among the tested species, C. vulgaris was most resistant to TBT, and the 7-d IC50 values measured in terms of cell number and chlorophyll content were 220 and 262 µg/l, respectively. The second most resistant species was C. sorokiniana (Wuhan isolate) and their IC50 value was around 100 µg/l. On the other hand, C. miniata (Hong Kong isolate) was the most sensitive species, their growth was strongly inhibited by TBT and the 7-d IC50 was 21 µg/l. For the three Scenedesmus species, S. dimorphus and S. platydiscus (both were isolates) had similar growth rate and similar 7-d IC50 (around 50 µg/l) but S. quadricauda had lower growth and was more sensitive to TBT (7-d IC50 value was 30 µg/l). Chlorella species were generally more resistance to TBT than Scenedesmus species except C. miniata. Results also showed that the IC50 values based on cell number were not significantly different from that based on absorbance at 650 nm. The acute 72-h IC50 values (based on 72-hour measurements) were comparable to the data taken at the end of the 7th day of exposure (7-d IC50).