Effects of trichlorobenzene on natural phytoplankton populations.

Natural phytoplankton assemblages from an offshore station in Lake Michigan were exposed to individual isomers of trichlorobenzene (TCB) and incubated in situ for a 24 h period. One set of exposures was initiated with a lake assemblage collected at 0330 h from 30 m and the TCB isomers added at 0400 h. The second exposure experiment was initiated with an assemblage from 30 m collected at 1530 h and the TCB isomers added at 1600 h.Comparisons of the chlorophyll a to neutral lipid ratio and the neutral to polar lipid ratios suggest that 1,2,3-TCB is more toxic than 1,2,4-TCB. Furthermore, more effects were observed when exposures were initiated at 0400 h when compared with a parallel experiment initiated at 1600 h. These studies with natural assemblages support culture studies of effect as a function of time of exposure.