Effect of ultra-low concentrations of TBT on the microalgae Tetraselmis sp. and Chattonella subsalsa

Bioencrustation is a natural process resulting from the colonisation and growth of organisms on solid substrates. For more than 40 years, Tributyltin (TBT) has been used as a biocide in antifouling paint. Since microalgae are constantly exposed to TBT, the growth of two microalgae species of the Guanabara Bay (Tetraselmis sp. and Chattonella subsalsa) was analysed in the present study. For this, the microalgae were grown using f/2 medium; potassium dichromate was used to guarantee the validity of the used method. To assess the effects on both genera of microalgae, different concentrations of TBT (ranging from 0.1 to 50 ng.L−1 diluted in f/2 medium) were used. All tests were carried out under a germination chamber, and the cell density was measured after 96 h. The results indicated that concentrations below 4.2 ng.L−1 were sufficient to inhibit 50% of the microalgae growth, demonstrating TBT can still be toxic even in ultra-low concentrations.