In order to monitor long-term variability and eventual changes in the planktonic community, a semiquantitative analysis of microplankton based on net sampling is ongoing weekly since 2020 at the Helgoland Roads station, before 9 a.m. The sampling is tightly linked to the LTER Helgoland Roads time series, thus enabling the coupling of species occurrences to the respective hydrochemical and physical conditions in the water column. These long-term data allow to quantify realized niches of frequently occurring microplankton species and to pinpoint rarely occurring species which cannot be detected in the quantitative plankton analysis.