Growth and Adaptation of Estuarine Unicellular Algae in Media with Excess Copper, Cadmium or Zinc, and Effects of Metal-Contaminated Algal Food on Crassostrea virginica Larvae

Abstract

Responses of the estuarine unicellular algae ~Monochrysis lutheri, Isochrysis galbana, Dunaliella euchlora, and Phaeodactylum tricornutum to excess CuCl,, CdCl,, and ZnC1, in growth media were determined. Tolerance to metals in artificial seawater was much greater than in enriched natural seawater, presumably because of the higher concentration of metal ligands in the former. Growth differences between species in media containing excess Cu or Cd were observed in both rnedla tested. Growth of M. lutheri and I. yalbana was inhibited considerably more than that of the other test organisms. This difference did not occur in media w ~ t h excess Zn. After extended periods of subculture in sublethal concentrations of Cu and Cd, algae developed tolerances to metal concentrations that were inhibitory upon initial exposure. Strains of I. galbanaadapted to grow in a medium with 10 mg% CuC1, (47.3 pprn Cu) or 2.5 mg% CdCl, (15.3 ppm Cd) were fed to laboratory-reared veliger larvae of the oyster Crassostrea virginica. These algal foods induced poor growth and high mortalities in grazing larvae. We conclude that pollution of estuarine waters with high concentrations of metals can decrease primary productivity and alter algal species dominance With continued exposure to sublethal concentrations, phytoplankters can exh~b i t a limited increase in tolerance and adaptation to the metals These populat~ons are then potentially toxic for grazing species at higher trophic levels.