Abstract
In New-Caledonia,rearing of the Pacifie blue shrimp, Penaeus stylirostris, currently represents a major socio economic activity. However, since 2005,massive unexplained larval mortalities have been affecting the hatcheries and threatening the entire production. The lageon seawater,used during larval rearings, possesses physico-chemical characteristics and microbial patterns which are likely to vary according to various natural and anthropic factors. Yet, water quality and microorganisms associated with the rearings influence larval survival. ln this context,this project aimed to define if variations of the prokaryotic communities associated with the larval rearings couId explain the observed larval mortalities. This work first evidenced vertical and horizontal transmissions involved during the establishment of the larval microbiota. The identification of a core microbiota, associated with ali the considered samples and initially present in the eggs and in the reservoir waters,suggests a lasting impact of these transmissions during the larval development regardless of the larval health status. Eutrophication of the rearing water was aIso highlighted in ali the rearings which were exposed or not to mass larval mortalities. We showed that this eutrophicatior as weil as antibiotic addition,larval development and larval health status induced variations of the prokaryotic communities associated with the larval rearings. Finally,bacterial biomark ers of larval health status were highlighted.