Variability of Trace-Metal Concentrations Within and Between Colonies of Pocillopora damicornis

Variations of cadmium, lead, copper, nickel and chromium concentrations in tissues and skeletons of the scleractinian coral Pocillopora damicornis were measured to provide information for designing bio-assay surveys involving this organism. Intra-colony variations were measured using multiple portions from individual colonies, and inter-colony variations were measured using single portions from different colonies of a coral community. We found that specific metals partitioned differently into tissue and skeletal parts, possibly because selectivity for each metal differed due to biochemical utility or toxicity. Intra-colony variations in metal concentrations were inconsistent, and skewed distributions of tissue-metal concentrations were sometimes observed. Overall, the application of tissues for heavy-metal bio-assays is compromised by inconsistent intra-colony variation, and the substantial material needed to represent tissue-biomass. In contrast, small replicate samples of skeleton can be collected from a colony, allowing representation of intra-colony metal variation with minimal damage to the organism.