Soil Organic Matter, Anaerobic Respiration, and Oxidation—Reduction

Abstract

Oxidation—reduction reactions are important in pond aquaculture because many biological processes that affect soil condition, water quality, and aquatic animal production are biologically mediated oxidations and reductions. Photosynthesis is a well-known reduction reaction; inorganic carbon in carbon dioxide is reduced to organic carbon in carbohydrate with the capture of energy. Aerobic respiration is an oxidation reaction in which carbon in organic matter is oxidized to carbon dioxide with the release of energy. Respiration by microorganisms decomposing organic matter in pond soil consumes oxygen faster than it can penetrate the soil mass, and only the surface layer is aerobic. Pond soil is vertically stratified according to electron acceptors used by microbes in respiration. Below the thin, aerobic surface layer where oxygen is the terminal electron acceptor in respiration are successive layers where nitrate, iron and manganese, sulfate, and carbon dioxide, respectively, are used as electron acceptors or oxidants in respiration. Fermentation also occurs in anaerobic soil.