The effects of DDT (2,2-bis-(p-chlorophenyl)-1, 1, 1-trichloroethane) on to develop a reasonable picture of its distribution in marine air, water, biota, or sediment. Present evidence shows DDT residues being found in widely separated geographical areas and in many levels of food chains, their concentrations increasing in the higher levels (8,16,18,19,25,26 The medium used to culture the phytoplankton was similar in composition to one described by Carlucci and Bowes (7).All species were bacteria-free. Sterility tests were made periodically by introduction of a small inoculum of the culture into peptone-enriched medium. Cultures were also checked for purity by phase microscopy.All glassware used in the experiment was rinsed with redistilled hexane and checked for the presence of DDT and related compounds.Culture vessels were 250-ml Erlenmeyer flasks. Each contained 150 ml of mediulm. The flasks were plugged with cotton 172 www.plantphysiol.org on May 11, 2018 -Published by Downloaded from