This collection contains freeze-dried subsamples of aquatic microalgae (NEON sample class: ptx_taxonomy_in.freezeDried). Periphyton, seston, and phytoplankton samples are collected three times per year at wadeable stream, river, and lake sites during aquatic biology bout windows, roughly in spring, summer, and fall. Samples are collected using the most approriate sampler for the habitat and substratum type, including rock scrubs, grab samples, and epiphyton. In wadeable streams, periphyton samples are collected in the two most dominant benthic habitat types (e.g. riffles, runs, pools, step pools), and seston samples are collected from the water column near the S2 sensor. In lakes, water-column phytoplankton samples are collected near the buoy, inlet, and outlet sensors using a Kemmerer sampler, and in littoral areas using the best benthic sampling method for the substratum type. In rivers, phytoplankton samples are collected near the buoy and two other deep-water locations using a Kemmerer sampler, and in littoral areas using the best benthic sampling method for the substratum type. Samples within this collection are preserved by freeze-drying. Samples are archived in 20 mL glass scintillation vials and stored at room temperature. See related links below for protocols and NEON related data products.