Above- and below-ground biomass of five species of mangroves was estimated for the Mary River, south-eastern Queensland. Below-ground : above-ground biomass ratios of species in the upstream reaches ( Avicennia marina , Aegiceras corniculatum and Excoecaria agallocha ) averaged <0.5, and those of species in the saline conditions of the mouth ( Avicennia marina , Rhizophora stylosa ) ranged between 0.9 and 1.5. Within the estuary mouth, above-ground biomass of Avicennia marina and Ceriops tagal decreased between frontal saline and upper-intertidal hypersaline environments, and this was reflected in the below-ground : above-ground biomass ratios, which increased to approximately 3.5 for both species.