Pollution from heavy metals has increased in recent decades and has become an important concern for environmental agencies. Arsenic, cadmium, mercury and lead are among the trace elements that have the greatest impact and carry the highest risk to human health. The aim of the present study is to compare the accumulation of Cd, Pb, Hg and As in the seaweeds collected from the coast of. Khanh Hoa. Because of that, the authors were interested to (1) determine the concentration range of heavy metals in seaweed species in Khanh Hoa
(2) describe the temporal variation of heavy metal concentrations in the seaweeds seasonal collections were done in March, April, May 2009, 2010, 2011. Lead, arsenic, mercury and cadmium contents were determined in 7 species of sea'weed in Khanh Hoa. The concentration ranges found, expressed in mg/kg dry weight, were: Pb (0.02-0.46) As (0.03-22.91), Hg (0.02-0.59) and Cd (0.03-1.16).