Long-term plankton and environmental monitoring dataset from the Marine Protected Area of the Iroise Marine Natural Park (2010–2023) in the Iroise Sea, North Atlantic

Abstract. This data paper presents a long-term monitoring dataset of phytoplankton (2010–2022) and zooplankton (2010–2023) communities, as well as associated environmental parameters (2010–2023), from the Iroise Marine Natural Park, Iroise Sea, North Atlantic, France's first Marine Protected Area. The dataset combines traditional microscopy-based phytoplankton counts with zooplankton data (abundances) obtained from digitized images using the ZooScan imaging system, along with surface and bottom temperature and salinity measurements. Sampling was conducted seasonally along two main transects and three coastal stations, capturing both spatial and temporal dynamics of plankton communities. Phytoplankton was identified at the species level by the same taxonomist during all the time-series (573 taxa in total). From their individual images, zooplankton was automatically sorted into 103 taxonomic and morphological groups, validated by an expert, and compiled into a data table allowing both community and individual approaches using abundances and biovolumes at both individual and community levels. Individual zooplankton images have also been made available for further morphometric analyses. This 14-year long, spatially and temporally resolved zooplankton imaging dataset is part of an ongoing effort to enhance the availability of zooplankton imaging data, locally and globally. This, as a whole dataset, can be used to study the influence of coastal-offshore environmental gradients on marine plankton biodiversity patterns, especially in protected waters at the intersection of the English Channel and the Atlantic Ocean, in a region characterized by the presence of the Ushant front.