Using biomonitors, which provide time-integrated measurements of the parts of the total ambient metal load that are directly relevant to ecotoxicology, it is possible to identify regional and/or temporal variations in the bioavailability of heavy metals in the marine environment. Heavy metal biomonitors must meet a number of specifications, not the least of which is that they must be metal accumulators. Recognition of the presence and relative magnitude of various metal sources is made possible by the use of a variety of biomonitors. To enable intra-specific comparisons of bioavailabilities between geographical locations, it is necessary to find extensive global biomonitors. The alga Ulva Lactuca, the mussels of the genera Mytilus and Perna, the oysters Ostrea and Crassostrea, the barnacles Balanus amphitrite and Tetraclita squamosa, and the talitrid amphipod Platorchestia platensis are examples of such global biomonitors. The requirement for accurate, precise taxonomic identification continues to be a significant caution in the deployment of such global biomonitors
