With the development of industry and agriculture, more and more heavy metals are released into water bodies.Today, many heavy metals constitute a global environmental hazard.Heavy metals such as copper, zinc, and nickel are essential for many physiological processes yet can be toxic at higher levels.Other metals such as cadmium, mercury and lead are nonessential and potentially highly toxic.Algae possess a range of potential cellular mechanisms that may be involved in the detoxification of heavy metals and thus tolerance to metal stress.These include roles for the following: for sequesteration of metals on extracellular components that reduce metal bioavailability;for chelation of metals in the cytosol by peptides and proteins;for sequestration of metals in polyphosphate bodies;for the com-partmentation of metals away from metabolic process by transporting them into the vacuole;for increasing the efflux or exclusion of metals;for producing stress proteins such as heat shock proteins that repair the stress-damaged proteins;in addition, some heavy metals cause oxidative stress in algae, with the result that metal toxicity can be altered by synthesis of appropriate enzymes or metabolites counteracting metal-induced oxidative stress. In recent years, some attempts to engineer the production of metallothioneins (MTs) and phytochelatins (PCs) in algae to increase metal tolerance and/or accumulation have been reported.To date, however, it is mainly the model plant species that have been genetically engineered.Phytoremediation strategies have been proposed as an attractive alternative owing to their low cost and high efficiency.The concept of phytoremediation of heavy metal contaminated water has been increasingly supported by research.And, algae have been widely used as pollution indicators in water quality determination.Thus, studies on tolerance and detoxification mechanism of heavy metal in algae have numerous ecological and public health implications.