Periphyton is an important primary producer throughout the Everglades ecosystem. It consists of an assemblage of algal, bacterial and fungal microbes and associated plants, detritus and aquatic invertebrates. Periphyton biomass and productivity can be high (often exceeding plants) in freshwater and marine sites in the FCE, and therefore is an important contributor to the base of the food web, prey refuge, soil formation, nutrient cycling and gas exchange. At FCE sites where periphyton is present, we measure biomass and productivity on a quarterly basis. Biomass is measured by harvesting periphyton from a measured area of substrate and quantifying its dry mass, ash-free dry mass and chlorophyll a content. We also measure the nutrient content (C, N and P) of the periphyton as a measure of nutrient exposure. Productivity is measured by incubating artificial substrates in situ for a measured period of time or by gas exchange in light and dark chambers. Subsamples are archived permanently to facilitate compositional or other content analyses.