Effect of lipid composition on the toxicity of trichlorobenzene isomers to diatoms. I. Short-term effects of 1,3,5-trichlorobenzene

Abstract

Cultures of Cyclotella meneghiniana and Melosira varians were split into four flasks. Two flasks of each taxon were used for exposure experiments and two were used as controls. Exposure to 1,3,5-trichlorobenzene was initiated in one flask of each taxon in the 1 lth hour of the light period on a 16:8 h L/D regime. Another exposure was initiated four hours later in the same day (the 15th hour of the light period) in the second experimental flask of each taxon. These experiments were conducted at 15°C and 20°C for 2–4 days and were analyzed for lipid class composition. Cyclotella demonstrated some short-term changes in lipid class composition when exposures were initiated in the 11th hour of the light cycle at 20°C and in both exposures at 15°C. In contrast, short-term effects were only observed in Melosira when the exposure was initiated in the 11th hour of the light period at 20°C. Control cells demonstrated periodicities in lipid composition that appeared to be entrained with the light/dark cycle. The cultures that demonstrated toxicity effects were characterized by low triacylglycerol content, low neutral/polar lipid ratios, and a pattern of chlorophyll synthesis at the time of exposure. It is suggested that rapidly growing cells are more susceptible to short term effects of this trichlorobenzene isomer. Furthermore, timing of the initial exposure may alter toxicity results and this may be a consequence of lipid class composition at the time of exposure.