This article describes the historical data series produced by the SRN network managed by Ifremer. Since 1992, the SRN (‘Suivi Régional des Nutriments’ in French; Regional Nutrients Monitoring Programme) network has been analysing phytoplankton species and measuring twelve physicochemical parameters at ten different stations distributed along three different transects located in the Eastern English Channel, and the Southern Bight of the North Sea. The SRN collects a maximum of 184 samples per year and detects up to 281 taxa, including harmful algal bloom species (HABs), with a bi-weekly to monthly sampling frequency (depending on the location and the season). The objectives of this monitoring program are to assess the influence of continental inputs on the marine environment, and their implications on possible eutrophication processes. It also aims to estimate the effectiveness of development and management policies in the marine coastal zone. The regular acquisition of data allows the establishment of a long-term monitoring of the evolution of coastal water quality, as well as the observation of the consequences of large-scale alterations and modifications that are more related to regional anthropogenic activities. This paper provides an overview of the main characteristics of SRN data (descriptive statistics and data series main patterns) as well as an analysis of temporal trends using specific numerical tools available as an R package to help make use of such data. Main results of several research projects are also highlighted providing the readers with examples of what is doable with such a data set.