During the previous H2020 framework program, we submitted in 2019 and in 2020 a European doctoral training network to the MSCA-ETN-ITN call. Our European Training Network aimed to train 15 early stage researchers (ESRs) at the interface between omics, modeling, and data sciences, to study the response of marine plankton to climate change and its impact on ecosystem services. Our consortium included 10 beneficiaries (including 2 non-academic) and 15 simple partners (including 11 non-academic). The building of this network was supported by the MRSEI Pré-Plankserv project in 2018-2019. Thus, our project had been very well evaluated during the previous calls, with a score of 87.60% for its first submission in 2019 and a score of 91.20% for its re-submission in 2020. With the implementation of the new Horizon Europe program, the H2020 MSCA-ITN call for will become the MSCA-Doctorates call, with significant modifications, and in particular a reduction of one third in the number of funded PhDs winthin the network, from 15 to 10 ESRs. Consequently, our doctoral training network will have to be modify and especially resized to respond to the future MSCA-Doctorates call. The MRSEI project "HorizonPlankton" therefore aims to support the re-submission of our European doctoral training network for the next Horizon Europe MSCA Doctorate call.