Ecological eects, transport, and fate of mercury: a general review

Mercury at low concentrations represents a major hazard to microorganisms. Inorganic mercury has been reported to produce harmful e€ects at 5 lg/l in a culture medium. Organomercury compounds can exert the same e€ect at concentrations 10 times lower than this. The organic forms of mercury are generally more toxic to aquatic organisms and birds than the inorganic forms. Aquatic plants are a€ected by mercury in water at concentrations of 1 mg/l for inorganic mercury and at much lower concentrations of organic mercury. Aquatic invertebrates widely vary in their susceptibility to mercury. In general, organisms in the larval stage are most sensitive. Methyl mercury in ®sh is caused by bacterial methylation of inorganic mercury, either in the environment or in bacteria associated with ®sh gills or gut. In aquatic matrices, mercury toxicity is a€ected by temperature, salinity, dissolved oxygen and water hardness. A wide variety of physiological, reproductive and biochemical abnormalities have been reported in ®sh exposed to sublethal concentrations of mercury. Birds fed inorganic mercury show a reduction in food intake and consequent poor growth. Other (more subtle) e€ects in avian receptors have been reported (i.e., increased enzyme production, decreased cardiovascular function, blood parameter changes, immune response, kidney function and structure, and behavioral changes). The form of retained mercury in birds is more variable and depends on species, target organ and geographical site. With few exceptions, terrestrial plants (woody plants in particular) are generally insensitive to the harmful e€ects of mercury compounds. Ó 2000 Elsevier Science Ltd. All rights reserved.