SCAPA will investigate the structural and dynamic attributes of the planktonic system in the Cantabrian Sea. This scientific objective will be in turn the base for a critical testing of the plankton indicators proposed by the Marine Strategy Framework Directive (MSFD) and for the development of new alternatives if necessary. SCAPA will carry out a crossed comparative approach enclosing the main modes of plankton variability; i.e. shelf, slope and oceanic waters with vertical resolution at seasonal and circadian time scales. It will study all planktonic components, from viruses to macrozooplankton at several organization levels (species, functional groups and trophic level), including also non-living organic matter derived from their activity (i.e. dissolved organic matter, aggregates and phaecal pellets). It will quantify production and biomass ratios across these organization levels and organic matter pools, specifically measure bacterial and primary production and downward fluxes (vertical migration and sediment traps) to diagnose food web structure and trophic pathways. SCAPA will focus on several aspects currently identified to present a deficit of information: seasonal variability in the oceanic domain (critical to implement indicators), the role of macroplankton (mainly at slope and oceanic domains) and microphagous gelatinous zooplankton, add on scarcely studied plankton vertical migration and quantification and quality of sinking biogenic material. The methodological approach takes advantage of the ongoing monitoring program RADIALES and will increase sampling effort to resolve vertical and circadian resolution at four times during the seasonal cycle. It includes a series of methodologies and techniques (e.g. flow cytometry, HPLC, plankton image analysis and automated classification) that are particularly efficient in sample time processing; a critical aspect for implementing plankton indicators, which have to be obtained by robust methodologies with reasonable costs and at operational temporal scales. SCAPA approaches the societal challenge of an ecosystem-based marine management, explicit in the European MSFD. Management actions related with the marine environment (e.g.: Fisheries) require implementing a series of indicators that resume the main structural and dynamic attributes of the plankton system. The latter is challenged, however, by the high complexity of the structure and dynamics of this system. Resolving this complexity is the main scientific objective of SCAPA. The development of indicators in marine ecology is in its founding state, although recently fostered by the MSFD.