ABSTRACT
Nutrients are the material currency of energy flow and structural form in biological systems. All essential elements, molecular structures not synthesized endogenously, and useful biochemical energy may be treated as nutrient entities. Biochemical and geochemical nutrient processes in aquatic habitats have been reviewed on a number of occasions. Fundamental molecular and physiological processes of nutrient uptake, metabolism, and storage in tropical aquatic ecosystems are identical to those operating in terrestrial and high latitude aquatic ecosystems. The elemental composition of organisms, community biomass, and derived detritus reflect organismal and ecosystem nutrient status. The generalization is frequently made that nutrient levels in tropical waters are lower than in comparable temperate systems. Nitrogen is the second most abundant nutrient element and, like carbon, exists in a wide range of organic forms although most nitrogen-containing molecules in living things tend to be constructed from a narrow range of organic building blocks.
