|abstract:||Submerged and floating mats of predominantly blue-green algae, commonly referred to as periphyton, are a conspicuous feature of the Water Conservation Areas (WCA). Periphyton are communities of microorganisms (primarily algae) that live attached to the surfaces of stems and leaves of aquatic plants and other submerged substrates. As primary producers, periphyton convert carbon dioxide, water and other nutrients into organic plant material which is foraged upon by a wide variety of Everglades invertebrates (amphipods, crayfish, snails, insect larvae, etc.) and juvenile fishes. In some portions of the everglades, periphyton carbon fixation and standing crop measurements have been shown to exceed adjacent macrophyte communities. Consequently, the periphytons represent an important primary food source of the Everglades food chain. Recent studies of algal populations in WCA-3A show that some blue - green algae have the ability to fix free nitrogen from the atmosphere and utilitize it for cell growth. As a result, periphyton can play an important role in the cycling of nitrogen in the marsh ecosystem.