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.

Effects of chlorinated benzenes on diatom fatty acid composition and quantitative morphology. I. 1,2,4-Trichlorobenzene.

Cells of the diatom Cyclotella meneghiniana were exposed in a closed system to 0.245 ppm 1,2,4-trichlorobenzene. Response to this chlorinated benzene was monitored over a period of 5 days by quantitative ultrastructure and fatty acid percent composition. Over the time period examined, 41 significant morphological changes and 12 significant changes in fatty acid composition were observed. Autophagic-like vacuoles were frequently observed, indicating lysis of cellular constituents. In general, there was an increase in the C20:5 fatty acid, which may be indicative of photosynthetic impairment, since this fatty acid probably substitutes for linolenic acid in diatoms. The most significant numbers of changes were observed after 8 hr of exposure to this lipophilic toxicant, and these changes occurred in membranous organelles. It is suggested that the daily photoperiodic variation in lipid content of phytoplankton may be an important consideration in evaluating effects of lipophilic toxicants.

Effects of chlorinated benzenes on diatom fatty acid composition and quantitative morphology. II. 1,3,5-Trichlorobenzene.

Cells of the diatom Cyclotella meneghiniana were exposed in a closed system to 0.245 ppm 1,3,5-trichlorobenzene. Response of the diatom was measured by quantitative ultrastructure and fatty acid percent composition over a 5-day period. During that time, 28 significant morphological and 13 significant fatty acid percent composition changes occurred. Autophagic-like vacuoles were observed consistently through the sampling periods. In comparison with exposure to 1,2,4-trichlorobenzene, 1,3,5-trichlorobenzene exerts fewer effects in the parameters studied, and these effects were observed most frequently in membranous components during the initial eight hours of exposure. It is suggested that the amount of cellular lipid and the relative reactivity of the isomer are responsible for the observed effects.

Effects of chlorinated benzenes on diatom fatty acid composition and quantitative morphology. III. 1,2,3-Trichlorobenzene.

Cells of the diatom Cyclotella meneghiniana were exposed in a closed system to 0.245 ppm 1,2,3-trichlorobenzene. Response of the diatom was measured by quantitative ultrastructure and fatty acid percent composition over a 5-day period. During that time, 35 significant morphological and 12 fatty acid percent composition changes occurred. The most pronounced morphological change that occurred was a significant increase in lipid volume. In addition, changes were observed in vacuolar relative volume, suggesting that the tonoplast became more permeable. Fewer significant changes were observed in fatty acid percent composition upon exposure to this isomer. However, there was a consistent increase in oleic acid (C18:1). The observed changes in morphological and fatty acid percent composition were uniformly distributed with time after the first hour of exposure. Results support the hypothesis that increased lipid stores may alter the timing of response to lipophilic toxicants.

Effects of chlorinated benzenes on diatom fatty acid composition and quantitative morphology. IV. Pentachlorobenzene and comparison with trichlorobenzene isomers.

Cells of the diatom Cyclotella meneghiniana were exposed in a closed system to 0.095 ppm pentachlorobenzene over a period of 5 days. Changes in fatty acid and morphological percent composition were monitored to determine the effect of the toxicant. The greatest morphological change observed was an increase in lipid volume. Most morphological changes occurred in the 1 hour and 5 day sampling periods. Few changes in morphological characteristics or fatty acid percent composition were observed at eight hours, when the cells were in the dark. The C18:1 and C20:5 fatty acids were most variable with exposure to pentachlorobenzene. Results suggest that at sublethal doses, lipophilic toxicants exert effects that are biphasic. That is, immediately measurable effects are observed in the cells that include increases in storage products and changes in membranous organelles. Long-term effects are postulated to be the result of mobilization of lipophilic toxicants that have partitioned into lipid stores and are more available when lipids are metabolized. Although pentachlorobenzene has a higher octanol/water partition coefficient, it appears to exert fewer cellular changes than any trichlorobenzene isomer.

Fine structure of the cell wall of the cyanobacterium Microcoleus vaginatus (Vauch.) Gomont.

The organization of the cell wall of Microcoleus vaginatus (Vauch.) Gomont is described. The four layered wall possesses an unusual layer 2 (mucopolymer containing layer). This layer is 20 nm thick near the crosswall, but abruptly increases in thickness to 90 nm away from the crosswall. In many filaments a perforated sheet 20 nm in thickness was observed on the face of layer 2 which is toward the plasma membrane. It is suggested that this sheet represents an area of mobilization of mucopolymer from layer 2. Electron dense deposits in the cytoplasm or in layer 1 are sometimes observed in association with the developing crosswalls. Junctional pores 12.6 nm in diameter, and spaced 19 nm apart were observed in the longitudinal wall on each side of the junction between the cross and longitudinal walls. Other pores through layer 2 were also observed. These 10 nm pores in the longitudinal wall were randomly arranged (15 to 40 nm apart) and were located on each side of the crosswall up to a distance of 0.6 micrometer from the junction. The relationship between the thickness of layer 2, and the diameter of M. vaginatus and other blue-green algae is discussed.

Phosphate metabolism in blue-green bacteria. V. Factors affecting phosphate uptake in Plectonema boryanum.

Plectonema boryanum requires approximately 5 days of exposure to a culture medium lacking phosphorus to induce the "polyphosphate overplus" phenomenon. At pH9, phosphate uptake is greatest both from normal culture medium and from dilute salt solutions. Phosphate uptake from dilute salt solutions was greatest when Na+ or K+ are combined with Ca2+ or Ca2+ and Mg2+. Cells starved of phosphorus in the presence of a high concentration of K+ or Ca2+ in the medium, and then allowed to take up phosphorus under the same conditions, assimilate more phosphorus than with other major ions.