ABSTRACT
Emphasis is placed on interactions among microbial processes at the sediment-water interface and spatial and temporal variations in the factors that control solute fluxes. Microbial regeneration of inorganic nutrients within sediments results in concentration gradients that force diffusion of the solutes from interstitial water in the sediments to the overlying water. The sedimentation rate of particulate organic carbon varies widely within and among lakes. Subsequent to the arrival at the sediment surface, particles are subject to resuspension via hydrodynamic forces, burial through bioturbation and sedimentation, and dissolution through chemical or biological processes. Sedimentation rates in lentic systems invariably exceed dissolution and mineralization rates so that particles eventually become buried below the oxic zone, where subsequent degradation occurs only through anaerobic metabolism. The presence or absence of oxygen determines the distribution of essentially all of the microbial processes responsible for the cycling of elements in sediments.
