Other Important Elements

In addition to the major nutrients carbon, nitrogen, and phosphorus, many minor elements play an important role in the function of freshwater systems. Such elements may function as essential micronutrients, or they may affect the biota by being toxic, or they play an indirect role by influencing the mobility and availability of other elements. This chapter covers the fundamentals of important minor elements in freshwaters, including their sources, forms, cycling, and transformations. This chapter also includes the biogeochemical cycle of sulfur, which is in fact an abundant macronutrient but is included here due to its close interaction with iron and manganese. The chapter also includes silicon, which is an element of key importance to specific organisms in freshwaters.