The observation of biogeochemical cycles and ecosystems has traditionally been based on ship-based platforms. The obvious consequence is that the measured properties have been dramatically undersampled. Recent technological advances in miniature, low power biogeochemical sensors and autonomous platforms open remarkable perspectives for observing the "biological" ocean, notably at critical spatio-temporal scales which have been out of reach until present. The availability of this new observation technology thus makes it possible to envision the development of a globally integrated observation system that would serve both scientific as well as operational needs. This in situ system should be fully designed and implemented in tight synergy with two other essential elements of an ocean observation system, first satellite ocean color radiometry and second advanced numerical models of biogeochemical cycles and ecosystems. This paper gives guidelines and recommendations for the design of such system. The core biological and biogeochemical variables to be implemented are first reviewed, trying also to identify those for which the observational demand is high although the technology is not yet mature. A review of the five platforms now available (gliders, floats, animals with sensors, mooring at eulerian site and ships) allows their specific strengths with regards to biological and biogeochemical observations to be identified as well as to point out the community plans with respect to ongoing implementation. The critical issue of data management is addressed, acknowledging that the availability of