The growth rates of two species of marine diatoms were reduced by polychlorinated biphenyls (PCB's), widespread pollutants of the marine environment, at concentrations as low as 10 to 25 parts per billion. In contrast, a marine green alga and two species of freshwater algae were not inhibited at these or higher concentrations. The sensitivity of these species to PCB's paralleled their sensitivity to DDT [1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane].
Abstract. Organic substances are suspected to influence the unpredictable, episodic blooms which characterize the planktonic pennate diatom Asterionella glacialis in certain coastal waters. Experiments to test its general responsiveness to organic enrichments in terms of growth rate and colony formation were carried out. An axenic clone was grown at 10° C, 0.039 l min‐1,12:12 LD cycle in Guillard's f/2 medium enriched with eight different organic substances. Growth rates in organically‐enriched media during exponential phase usually exceeded those in f/2 medium alone. Cell yields after 12 days in media enriched with glycyl‐glycin and trypticase + yeast extract were significantly greater than in the other treatments. Longer chain lengths accompanied organic enrichment, notably with trypticase + yeast extract and 100ppm soil extract. These results suggest that Asterionella glacialis is positively responsive to elevated levels of certain organic substances. A potential effect of organic substance ‐ trace metal ‐ silica interactions on colony‐size is suggested.
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