Oceanic productivity, fishery yields and the net marine sequestration of atmospheric greenhouse gases are all controlled by the structure and function of planktonic communities. Recent studies have documented increases in the magnitude of phytoplankton developments in various parts of the World Ocean in coastal areas as well as in remote oceanic sites. In the coastal ecosystems the increased phytoplankton bloom magnitude of the last decade has been hypothesized to originate from increased upwelling or coastal eutrophication. In the North–western Mediterranean there does not exist any complete data set of simultaneous time–series of bacteria, phytoplankton, and zooplankton.
Therefore, there is an important need for the monitoring of bacterial, archaeal and protistan communities in combination with other environmental data to provide not only a comprehensive data set on physical and biogeochemical characteristics but also on processes. The monitoring of biological community structures of the continuum bacteria–phytoplankton–zooplankton–resources, the latter including benthic and pelagic organisms will give new insights in :
1) the characterization of community dynamics for the definition of functional types to be taken into consideration in complex biogeochemical–ecological–physical coupled models ;
2) the temporal trends of ecosystem structure changes.