Abstract. The French coast of the eastern English Channel (ECC) is classified as a potential eutrophication zone by the Oslo and Paris (OSPAR) Convention and as moderate to poor according to the phytoplankton quality element of the Water Framework Directive (WFD). It is regularly affected by Phaeocystis globosa bloom events, which have detrimental effects on the marine ecosystem, economy, and public health. In this context and to improve our observation strategy, MAREL Carnot, a multi-sensor oceanographic station, was installed in the eastern English Channel in 2004 at the Carnot wall in Boulogne-sur-Mer. The aim of this station was to collect high-frequency measurements of several water quality parameters to complement conventional low-resolution monitoring programs. The purpose of this paper is to describe the MAREL Carnot dataset and show how it can be used for several research objectives. MAREL Carnot collects high-frequency, multi-parameter observations from surface water as well as meteorological measurements and sends the data in near real-time to an onshore data center. In this paper, we present several physical, chemical, and biological parameters measured by this station. We also demonstrate that the MAREL Carnot dataset can be used to assess environmental or ecological statuses and conduct research in the field of marine phytoplankton ecology and oceanography. In addition, we show that this dataset may indirectly aid in improving European environmental management strategies. The MAREL Carnot dataset is publicly accessible via https://doi.org/10.17882/39754 (MAREL Carnot, 2023).