Regional and seasonal variations of trace metals in tropical Phaeophyceae from North Queensland

The brown algae Padina tenuis and P. tetrastromatica were selected as indicator organisms to monitor levels of ten metals (Fe, Cu, Co, Cd, Ni, Cr, Ag, Pb, Mn, Zn) in seawater from stations within Halifax Bay, Cleveland Bay, and Bowling Green Bay, near Townsville, on the northeast coast of Australia. Samples were collected monthly for one year to determine regional and seasonal variations of metal concentrations. The highest Cu, Pb and Zn concentrations in algae were found at the Townsville Harbour station in Cleveland Bay. However, seawater samples from the Harbour and Bowling Green Bay showed significantly higher levels only for Zn in the harbour waters. Furthermore, levels of dissolved Cd and Mn did not differ significantly between the two stations whereas levels of both metals were significantly lower in algae from the Harbour. It was concluded that the availabilities of, at least, Cd, Pb and Mn to algae were not readily identified by the techniques employed. Location-dependent variability was observed regarding correlations between metal pairs in algae and in those metals which were significantly correlated with temperature and salinity changes.