Effects of tributyltin on the chlorophyll contents of marine microalga Tetraselmis tetrathele, Nannochloropsis oculata and Dunaliella sp.

Abstract

Three species of marine microalga Tetraselmis tetrathele, Nannochloropsis oculata and Dunaliella sp., the important phyto-plankton in many hatcheries, were used in an acute toxicity test of TBT with emphasis on the chlorophyll a and b contents. After a very short exposure time of three concentrations of TBT, 0.1, 0.5 and 1μgl^<-1>, the three species of algae showed different responses. The chlorophyll a and b contents of T. tetrathele in all treatments were higher than those in controls, even be doubled in 1μgl^<-1> of TBT. N. oculata and Dunaliella had a slightly higher chlorophyll a and b contents in the lowest TBT concentration tested (0.1μgl^<-1>) than those in control, but as the TBT concentration increased their chlorophyll contents decreased. Three levels of TBT tested are within the range of the no observable effect concentration (NOEC) for T. tetrathele, while the lowest observable effect concentrations (LOEC) for N. oculata and Dunaliella are between 0.1 to 0.5μgl^<-1>. Among the three species, N. oculata has a highest sensitivity towards TBT.