Cadmium effects on growth and physiology ofUlva lactuca

Abstract

The chlorophyceanUlva lactuca L. was grown in the laboratory in unialgal culture to sufficient size so that up to 70 discs, 24 mm in diameter, could be punched out of a single plant. Using such discs,U. lactuca was then tested with various concentrations of Cd under continuous-flow conditions. A concentration of 4.5 ppm Cd was lethal toU. lactuca within 6 days. Control discs in unpolluted water increased in diameter at a rate of 8 to 13 % day⁻¹ over a 6-day period. At sublethal concentrations of Cd a sharp reduction in growth rate was observed at increasing concentrations up to approximately 0.3 ppm Cd, whereas from 0.3 ppm Cd to the lethal concentration the reduction of the growth rate was significantly less. Reduction in photosynthetic performance corresponded closely to the reduction in growth rate. At ambient concentrations of 0.8 ppm Cd, the plants concentrated Cd by a factor of approximately 50 in 6 days. Much higher concentration factors were attained in lower ambient concentrations. After removal from Cd-polluted water into flow-through culture in unpolluted water, a subsequent loss of Cd was indicated and the plants recovered rapidly. Plants exposed up to 3 d to 0.7 ppm Cd recovered sufficiently to produce viable gametes 7 days after removal from Cd. Because it has a relatively short life span and apparently loses Cd subsequent to exposure to Cd-polluted water,Ulva lactuca is not recommended as an alga for monitoring in-situ environmental pollution.