ANOXIA defines the lack of free molecular oxygen in an environment. In the presence of organic matter, anaerobic prokaryotes produce compounds such as free radicals, hydrogen sulfide, or methane that are typically toxic to aerobes. The concomitance of suppressed respiration and presence of toxic substances suggests these habitats are inhospitable to Eukaryota. Ecologists sometimes term such environments 'Death Zones'. This book presents, however, a collection of remarkable ad