EFFECT OF FUEL-OIL AND DISPERSANT ON CELL-CYCLE AND MACROMOLECULAR-SYNTHESIS IN THE CHLOROCOCCAL ALGA SCENEDESMUS-ARMATUS

Growth and reproductive processes in synchronous cultures of the alga Scenedesmus armatus (isolated from Baltic phytoplankton) were followed in the presence of various concentrations of dispersant DP-105, oil, and mixtures of oil and dispersant. The inhibition of protoplast fissi on was the most prominent effect of oil. Nuclear division was inhibite d to a lesser extent. With an increasing concentration of oil, dispers ant, or a mixture of both, the inhibitory effects were expressed earli er. The presence of oil compounds did not effect the timing of DNA rep lication, but it did reduce the number of replication rounds in a conc entration dependent manner. The inhibition of DNA synthesis was accomp anied by slightly delayed cessation of RNA and protein synthesis. Star ch synthesis was always inhibited to a lesser extent, and at a later t ime, than other macromolecular syntheses. Pigment synthesis continued almost to the end of the cell cycle. Thereafter, a rapid degradation o f all pigments began and the cells became bleached. No inhibitory effe ct on reproductive processes was found if oil or dispersant were added to cultures transferred into darkness. Furthermore, recovery from inh ibition of reproductive processes caused by oil in continuously illumi nated cultures was observed in darkened cells. Chemically dispersed fu el oil was only slightly more toxic than mechanically dispersed fuel o il; an additive, rather than synergistic, effect of oil/dispersant mix ture was found.