Evaluation of the metal content of farm grown Gracilaria tikvahiae and Saccharina latissima from Long Island Sound and New York Estuaries

In the US, seaweed aquaculture is still a developing industry. Since a significant number of seaweed farms are located in urbanized estuaries, cultured seaweeds could accumulate contaminants such as heavy metals. A warm temperate red algal species, Gracilaria tikvahiae and a cold-water brown algal species, Saccharina latissima were cultivated at three sites in Long Island Sound (LIS) and New York (NY) estuaries to biomonitor potentially toxic metals. Metal concentrations were below almost all national and international regulatory limits for human consumption. For example, the highest measured concentrations of Hg in tissue samples of G. tikvahiae and S. latissima are 88–93% less than the limit set by the Food and Drug Administration of the USA. Concentration maxima of Cd in G. tikvahiae and S. latissima were 20% and 32%, respectively, lower than stringent French limits. Maximum levels of Pb in tissue samples of G. tikvahiae (but not S. latissima) were close to the French limits at the NY estuary site. These results indicate generally that heavy metal contents of seaweeds cultivated urbanized estuaries should be monitored since accumulation appears to be site-dependent. The great capacity for the accumulation of nitrogen and other nutrients in seaweed tissues, improving water quality, is also accompanied by the uptake of other, less desirable materials.