The objective was to determine the spatial-temporal distribution of total mercury (T-Hg) bioavailability at the Goiana Estuary using Anomalocardia brasiliana as model organism. Two seasons (rainy in February and dry in August), three habitats of the tidal flats (upper, middle and lower) and two size classes (<20 mm and &gt;20 mm) were considered. In addition, depurated and non-depurated samples were tested. Individuals (N = 600) were pooled in samples representing the combinations of the above situations. T-Hg in the tissues of the pooled samples of A. brasiliana from Goiana Estuary varied from 0.06 and 0.18 &#956;g g-1 dry weight. Significant differences occurred between treatments (P < 0.05). In average (10-30%), after depuration T-Hg concentrations decreased, especially at the tidal flat areas most exposed to tidal variations (upper and middle). There were no significant differences between seasons or size classes.