TOXIC METALS IN AQUATIC ECOSYSTEMS - A MICROBIOLOGICAL PERSPECTIVE

Microbe-metal interactions in aquatic environments and their exact rol e in transport and transformations of toxic metals are poorly understo od. This paper will briefly review our understanding of these interact ions. Ongoing research in Lake Chapala, Mexico, the major water source for the City of Guadalajara, provides an opportunity to study the mic robiological aspects of metal-cycling in the water column. Constant re suspension of sediments provides a microbiologically rich aggregate-ba sed system. Data indicate that toxic metals are concentrated on aggreg ate material and bioaccumulate in the food chain. A provisional model is presented for involvement of microbial aggregates in metal-cycling in Lake Chapala.