Effect of Trichodesmium blooms on water quality in the Great Barrier Reef lagoon

Abstract

Studies carried out in Cleveland Bay and John Brewer Reef, C Great Barrier Reef, show significant changes in water quality during the presence of Trichodesmium blooms. Elements most affected include particulate Fe and Mn, dissolved Mn and Ni, as well as pH, suspended sediments, phosphate, nitrate, chlorophyll-a and ammonium. Cd, Pb and Cu ions in seawater become more bioavailable during the presence of Trichodesmium. Coincident with the increased bioavailability of trace elements during the blooms, significant and sustained increases in total Fe, Zn, Cd, Cu, Ag and Mn occurred in black lip oyster Saccostrea amassa. Levels of Zn, Cd, Cu in S. amassa exceeded health guidelines by 8000%, 4000% and 3000% respectively. Increased bioavailability of some trace elements during Trichodesmium blooms may also be a cofactor along with anthropogenic input for the increased metals in these oysters. -from Author