FIG. 4.

Effect of PQ on the growth of two diatom species and a phytoplankton-diatom natural assemblage. (A) Filtered (pore size, 63 μm) seawater; (B) C. fusiformis. (C) T. weissflogii. C. fusiformis and T. weissflogii were grown in f/20 media, and all preparations were treated with PQ and grown with a cycle consisting of 12 h of light and 12 h of darkness. Cell density and fluorescence were monitored by flow cytometry. The insets show the results for ethanol controls for each treatment. Grey squares, control (no PQ); open symbols, PQ concentrations between 0.1 and 100 nM; ♦, 1 μM PQ; •, 10 μM PQ; ▴, 100 μM PQ.