Mnemiopsis leidyi is an invasive gelatinous organism native to the American Atlantic coasts. This organism was observed for the first time in 2005 in the Berre pond. The Berre pond is the largest lagoon in Europe. This area, which was heavily industrialized in the past, is now undergoing rehabilitation. Due to its physiological characteristics, Mnemiopsis leidyi (or sea nut) has all the assets to be an invasive species: high spawning rate, voracious carnivorous predator, high growth rate, high abundance. My thesis is an interdisciplinary thesis linking an oceanography laboratory (MIO) and a human and social sciences laboratory (LPED). The introduction of an invasive species could attenuate the rehabilitation efforts implemented since 2006 by Europe. The aim is therefore to understand the impact of Mnemiopsis leidyi on zooplankton, and to determine the impacts of the proliferation of gelatinous organisms on human activities (pleasure boating, swimming, professional fishing). Thanks to this study we will try to implement management measures.