Phytoplankton are the autotrophic (self-feeding) components of the plankton community and a key part of oceans, seas and freshwater basin ecosystems. The name comes from the Greek words phyton, meaning plant and planktos, meaning wanderer or drifter. Most phytoplankton are too small to be individually seen with the unaided eye. However, when present in high enough numbers, some varieties may be noticeable as colored patches on the water surface due to the presence of chlorophyll within their cells and accessory pigments (such as phycobiliproteins or xanthophylls) in some species. This data collection activity includes sampling of phytoplankton within the Burrishoole catchment lakes Lough Feeagh and Lough Furnace. Phytoplankton has been sampled on a continuous basis since 2008. Phytoplankton has been collected via water samples and laboratory analysis. Phytoplankton has been sampled to support information and knowledge on the health of the catchment lakes ecosystem. Phytoplankton has been collected by the Newport catchment facility team of the Marine Institute. Dataset complete for the samples collected since the activity became operational.