ABSTRACT
The cycles of chemical elements and substances are interrelated with biological, geochemical and physical processes. The distribution and concentration of elements and substances in water depend on ‘fi xation’ and the active concentration of macronutrients (carbon, hydrogen, nitrogen, phosphorus and sulphur) and micronutrients (magnesium, iron, copper and zinc). Macronutrients and micronutrients alike are found in living organic matter, particulate matter, decomposing matter, or dissolved in water. The nutrient recycling rate depends on the interactions between vertical and horizontal mixing and the activity and biomass of aquatic organisms.
