Optical remote sensing (satellite ocean color) has demonstrated the capability to provide synoptic information of the optical and biogeochemical properties of the oceans. This is based on the determination of the spectrum of the water leaving radiance (i.e., the radiance emerging from below the sea surface obtained from the top-of-atmosphere signal corrected for the atmospheric perturbation). The amplitude and spectral shape of this primary geophysical ocean color product (i.e., the remote sensing reflectance), is then interpreted in terms of derived products such as concentrations of optically significant constituents or inherent optical properties for bio-geo-chemical and environmental applications at global or regional scales. Specifically, satellite ocean color has given another dimension to marine biogeochemistry and ecosystem studies, offering new opportunities for direct monitoring of biodiversity and shelf – sea fronts providing key information for instance on the timing and spatial distribution of plankton blooms, the magnitude of primary production and provision of environmental data layers crucial for building predictive models of species (fish and other pelagic animals) and habitat distributions, relevant for the implementation of important EU environmental policies (Water Framework Directive, Marine Strategy Framework Directive) and climate change projections. The main limitation in the operational use of satellite ocean colour data in the Black Sea and in other marginal seas is the lack of regional bio-optical algorithms linking the satellite signal to the specific bio-optical indicators. In fact operational satellite products generally rely on algorithms developed for global applications which are the source of large uncertainties (on the order of hundred percent for chlorophyll a) in the Black Sea coastal areas due to their optical complexity. This urges reinforcing efforts on the development of specific regional bio-optical algorithms by relying on in situ reference data sets of statistically representative and comprehensive bio-optical measurements. The reference bio-optical data, in addition to support algorithms development, will also be essential for the assessment of standard Sentinel-3 ocean colour data products delivered by Copernicus Marine and Climate Change services.