Aquatic Plants and Attached Algae

Both aquatic plants (macrophytes) and attached algae (periphyton) function as primary producers in lakes, but their roles in littoral zone dynamics are distinct. Although periphyton grows on all surfaces with sufficient light, macrophytes are usually restricted to low energy, depositional environments. Macrophytes form a complex 3-dimensional structure that can fill the water column, and are critical habitat for macroinvertebrates and fish. However, macrophytes appear to enter the food web primarily after decomposition. Periphyton is more cryptic, rarely extending more than a few centimeters into the water column. However attached algae are both highly productive and heavily grazed, contributing substantially to secondary production. The role of littoral primary producers in organic carbon and nutrient cycling is understudied relative to phytoplankton, but they can dominate primary production in small and oligotrophic lakes. Limited data suggest a high potential for macrophytes and periphyton to regulate nutrient flux into and out of the littoral sediments, and indicate that littoral primary producers compete with phytoplankton for inorganic nutrients under oligotrophic conditions. Spatial and seasonal variation in biomass, productivity, and taxonomic composition are poorly described for periphyton. The perception of intractable spatial heterogeneity has hampered the integration of littoral primary producers into models of lake ecosystem function