Deliverable report of the project H2020 SEAMLESS (grant 101004032). The scope of this document is (i) to report on the developments of weakly coupled ensemble assimilation methods and assimilation experiments performed in Work Package 4 (Task 4.1) of SEAMLESS, and (ii) to provide methodological recommendations to perform weakly coupled physical-biogeochemical data assimilation in the CMEMS MFC 3D domains.