Photosynthetic response of Halophila ovalis to heavy metal stress

This paper deals with the photosynthetic effects of a range of heavy metals on the seagrass Halophila ovalis. In this study, the photosynthetic respon se of laboratory-cultured II. ovalis to four heavy metals (Cu, Cd, Pb, Zn) was investigated. The results indicated clearly that chlorophyll a fluoresc ence was effective in monitoring the onset and development of stress, and o ccasional recovery, of H. avails when exposed to a wide range of heavy meta ls. Heavy metals in concentrations from 1 to 10 mg litre(-1) produced sever al acute toxic responses. They had a variety of effects on the photosynthet ic processes of this seagrass, with Cu and Zn having substantially greater effects than Pb and Cd. Quantum yield was the most sensitive measure of the photosynthetic processes affected by all heavy metals tested. With some ex ceptions, photosynthetic pigment content generally confirmed the chlorophyl l a fluorescence responses. (C) 1998 Elsevier Science Ltd. All rights reser ved.