Nucleation and new particle formation in the marine atmosphere is usually associated to the presence of macroalgea emerged at low tides in coastal areas, while these processes were very rarely detected away from coastlines. In the present study, we evidence the formation of new particles from the 1 nm size above the seawater surface in the absence of any macroalgea population. Within the SAM project (Sources of marine Aerosol in the Mediterranean), coastal seawater mesocosmss experiments were deployed in May 2013 at the Oceanographic andSTARESO Marine Station STARESO in western Corsica, with the goal of investigating the relationship between marine aerosol emissions and the sea water biogeochemical properties. Three mesocosms imprisoned 3. ,3 m3 of seawater each and their emerged part was flushed with filtered natural air. One of these mesocosms was left unchanged as control and the two others were enriched by addition of nitrates and phosphates respecting Redfield ratio (N:P = 16) in order to create different levels of phytoplanctonic activities. We followed both water and air characteristics of three mesocosms during a period of three weeks with by using online water and atmospheric probes and as well as seawater daily sampling daily samples for chemical and biological analysis of the sea water. Secondary new particle formation was followed on-line in the emerged parts of the mesocosms, using a SMPS for the size distribution above 6 nm and a Particle Size Magnifyer (PSM) for the number of cluster particles between 1 and 6 nm. We will present howThe results indicated that the cluster formation rates and early growth rates were related to the gaz-phase emissions from the seawater and to its biogeochemical properties. In the present study, we evidence the formation of new particles from the 1 nm size above the seawater surface in the absence of any macroalgea population.