Trace metal concentrations in marine macroalgae from different biotopes in the Aegean Sea

The commonest species of red, brown, and green macroalgae were sampled from a range of biotopes in the Aegean Sea and analysed for five different trace metals. Significant differences in metal concentrations were found among different seaweed species from the same biotope. The concentrations of metals in the various seaweed species may reflect their morphology, with those having a larger surface area having a greater internal content. Different species of seaweed have different affinities for different heavy metals. This may reflect competition between metals for binding or uptake sites in the seaweed. Comparing metal concentrations in algae among the studied sampling stations clearly indicates that the degree of accumulation depends not only on human activities but also on the geology of the specific area. While seaweed can be used successfully to assess the levels of heavy metals in the marine environment, not all elevated concentrations of heavy metals necessarily reflect increased levels of pollution. Indeed, the high concentrations of certain metals, e.g., Ni, found in our seaweed samples reflected the metaliferrous nature of the rock. It is therefore important to take account of a region's geology before attempting to interpret the data.