Physiological responses of five seagrass species to trace metals

Trace metal run-off associated with urban and industrial development poses potential threats to seagrasses in adjacent coastal ecosystems, Seagrass fr om the largest urban (Moreton Bay) and industrial (Port Curtis) coastal reg ions in Queensland, Australia were assessed for metal concentrations of iro n (Fe), aluminium (Al), zinc (Zn), chromium (Cr) and copper (Cu), Trace met al concentrations in seagrass (Zostera capricorni) leaf and root-rhizome ti ssue had the following overall trend: [Fe] > [Al] > [Zn] > [Cr] > [Cu]. Rai nfall events and anthropogenic disturbances appeared to influence metal con centrations in seagrasses with the exception of Al, which does not appear t o bioaccumulate, In laboratory experiments, five seagrass species (Halophil a ovalis, H. spinulosa, Halodule uninervis, Z. capricorni, Cymodocea serrul ata) were incubated with iron (1 mg Fe l(-1)) and copper (1 mg Cu l(-1)) an d responses assessed by changes in PSII photochemical efficiency (Fv/Fm), f ree amino acid content and leaf/root-rhizome metal accumulation. Iron addit ion experiments only affected Halophila spp, while copper additions affecte d other seagrass species as well, Trace metal contamination of seagrasses c ould have ramifications for associated trophic assemblages through metal tr ansfer and seagrass loss, The use of photosystem II photochemical efficienc y as well as amino acid concentrations and composition proved to be useful sublethal indicators of trace metal toxicity in seagrasses. (C) 2000 Publis hed by Elsevier Science Ltd.