Heavy metals enter the world's waterways from different sources, particularly road runoff, which carries zinc, lead and copper -- as well as smaller amounts of nickel, cadmium and other metals -- into storm drains and out to sea. Industrial waste also sends significant amounts of heavy metals into the oceans and rivers. These metals sink to the bottom and marine life, especially algae, absorbs them.
Numerous algae species occur throughout the world, with some forms such as brown algae thriving in highly polluted areas. Algae absorb heavy metal toxins and carry them throughout their lifespan. Some forms of microalgae can bind up to 10 percent of their biomass with metals. Biodiversity suffers in areas with high concentrations of metals, so algae species that survive in those areas demonstrate a high tolerance to metal toxicity.
Because algae accumulate heavy metal toxins quickly and carry them in all parts of the organism, measuring the levels of heavy metals in algae populations throughout the world provides information about pollution in the world's waters. By observing annual fluctuations in the bioaccumulation of metals in algae, the location and amount of heavy metal pollution can be tracked.
Research into clearing the waters of heavy metals has exploited algae's ability to absorb these toxins. Transgenic, or genetically altered, algae forms have been developed with heightened capacities for binding metals in their tissues. These algae variants are grown for the specific purpose of bioabsorbing heavy metals and and removing them from contaminated waterways. When introduced into polluted areas, these transgenic algae species spread quickly, drawing toxins from the water at a greater rate than naturally occurring algae can do.