Cyanotoxins: New Generation of Water Contaminants

Abstract

Cyanobacteria, more commonly known as blue-green algae, are found worldwide in various aquatic environments as well as in water distribution systems Atikovic 2003; Carmichael 1994; Madigan et al. 2003 . Blooms of cyanobacteria have recently become spatially and temporally more prevalent in the United States and worldwide as a consequence of increasing nutrient levels such as nitrates and phosphates from fertilizers and detergents. Cyanobacterial blooms impart color, odor, and taste problems in water. More importantly, such blooms produce and release toxic compounds that dramatically impair the quality of water bodies. Up to 50% of the recorded blooms can be expected to contain toxins Carmichael 1992 . These compounds have severe and sometimes irreversible effects on mammalian health. Episodes of human and animal poisoning by consumption of water contaminated with cyanobacterial toxins have been reported since the late 1800s Carmichael 1994 . Exposure to cyanobacterial toxins can affect the number and diversity of wild animal populations, cause bioaccumulation of toxins in the tissues of fish and shellfish, and indirectly affect other organisms through the food chain. Moreover, the presence of cyanobacteria and cyanobacterial toxins in sources of drinking water supply has raised major concerns. Another major issue is the lack of guidelines or regulations of cyanobacteria and cyanotoxins in terms of maximum contaminant level MCL and analytical detection methods. In the past few years, major research effort has been targeted toward the treatment of these toxins, especially the hepatotoxin microcystin-LR MC-LR . Cyanobacteria are present in various aquatic environments, including water distribution systems and can produce scum usually greenish observed at the bottom and surface of lakes. In ecosystems, the presence of cyanobacteria is crucial as they provide oxygen to specific aerobic microorganisms symbiotic living , convert inorganic nitrogen to organic forms that plants and phytoplankton can utilize and act as a source of energy to zooplankton primary producers . Recent studies have shown that zooplankton consumes cyanobacterial algal blooms selectively depending on the availability of food. The nonconsumable blooms can be lethal to or can reduce the number and size of progeny of zooplankton Carmichael 1994 . Cyanobacteria contain and release toxins as a metabolic byproduct and also