Nutrient Stoichiometry in Aquatic Ecosystems

In chemistry, the term ‘stoichiometry’ refers to the number of atoms of elements on both sides of a reaction. Stoichiometry tells you how many different molecules of each type of reactant you need to generate a specific product or set of products. Ecologists and limnologists can use these same principles of stoichiometry to understand aquatic ecosystems because individual species, like molecules, have defined chemical composition. The elemental formula of an individual species is normally not as strictly defined as the kinds of molecules we are most accustomed to thinking about, those with specific, unvarying composition. However, stoichiometry can still be a very useful approximation. Stoichiometry has much to say about the linkage of cycling of different elements and about patterns of nutrient limitation in primary producers and other parts of food webs. It bridges studies on individual species with studies dealing with the flow of matter and energy in ecosystems.