Effect of Humic Acids on Mercury Toxicity to Marine Algae

Humic acids extracted from the sediment of Cochin inshore areas exhibited impairment of mercury toxicity to marine algae maintained in Walne's medium under laboratory conditions. Cultures of marine micro alga Isochrysis galbana contaminated with sublethal concentration of 10 ppb of inorganic mercury and 10 ppm humic acids registered 18%, 21% and 37% increase in oxygen production for two, four and six hours incubation in light respectively, when compared to the controls. Similarly the daily growth rate of seaweed Ulva lactuca registered 26% increase over the control when the seaweed was maintained in medium containing 30 ppb Hg and 30 ppm humic acids. The results are discussed in the light of employing humic acids as growth promoter of marine algae as well as abetting agent of mercury toxicity.