DDT residues in marine phytoplankton: increase from 1955 to 1969.

Phytoplankton samples collected in Monterey Bay, California, from 1955 to 1969 contained compounds identified as p,p'-DDT, p,p'-DDD, and p,p'-DDE. Total concentrations of these compounds were approximately three times greater in the later samples. Lower concentrations throughout the period were associated with higher densities of standing crop.