This dataset supports the recent publication "Microplastics increase the marine production of particulate forms of organic matter" by L. Galgani et al (2019) in ERL. It comprises all data presented in the manuscript and Supplementary Information. In the file, Control = mesocosm without plastic addition (1,2,3) and MP = mesocosm with plastic addition (1,2,3). The data proceed from the MESO-Plastic experiment in 2017 conducted at the Hellenic Center for Marine Research, a member of the European Aquacosm network of mesocosm facilities