Modeling of intra-annual abundance distributions: Constancy and variation in the phenology of marine phytoplankton species over five decades at Helgoland Roads (North Sea)

•Complex phenological response of phytoplankton species related to warming.•Temperature accounts for seasonally different proportions of phenological variation.•Shifts in timing are differently related to shifts in biomass.•Constant and extending species-specific phenological time slots co-occur.•Superposition of anthropogenic and hydro-climatic drivers forms local fingerprint.