Mean and standard deviation of the trace metal concentrations in Tivela mactroides, Crassostrea rhizophorae and Thalassia testudinum tissues from the two sampling times are presented in Tables 4, 5 and 6, respectively. Significance levels were fixed at p < 0.05 on 95 % confidence level. For each organism studied, mean values of metals with significant concentration differences between the sampling sites are marked by an asterisk.