Description: Light can be a key driver of diatom assemblages, influencing overall cell densities, biovolumes, and diatom assemblage structure. Light availability in aquatic systems can be limited by both canopy cover in riparian areas and physical parameters, including depth and suspended sediments. For example, in headwater systems, light is often restricted by terrestrial canopy cover, resulting in a low light-adapted diatom assemblage that is altered in composition with the reduction of canopy cover. In contrast, turbid rivers in aridland regions often lack canopy cover but do carry high sediment loads that result in diatom communities growing in compressed habitats along shallow sandbars and bank edges with sufficient light penetration to support photosynthesis. This presentation examines the role of light in shaping diatom diversity and structure in stream and river systems that are light-limited or co-limited by other environmental drivers, including discharge and depth.

Target audience: Analysts and researchers interested in environmental drivers of diatom assemblages, stream and river ecology, headwater and aridland river systems, and water management issues.