It is generally well established that coastal lagoons continously enrich the adjacent seas. However, the function of hypersaline lagoons, also called negative estuaries, located inside marine regions influenced by upwelling waters, is no clear. In this paper, observations on the temporal variability of interactions between La Restinga lagoon and the adjacent Caribbean Sea are presented. Two stations, one located in the channel of the lagoon and other located in the open sea, three miles southeast and windward off the first station, were sampled every 10 days during a year (April/84 to March/85). Ecological variable like temperature, salinity, oxygen, chlorophylls, primary production and zooplankton abundance were studied. Channel water (St.1) showed higher temperature and salinity, but less oxygen than open waters (St.2). In Station 1, chlorophyll pigments reached their highest concentrations from July to October and lowest values from January to April. A similar tendency was shown for primary production values i.e. 800 mgC/m3/day from May to November and 350-450 mgC/m3/day from December to April. On the other hand, in the Station 2 located in the adjacent sea, the picture was inverse and highest values were found from December to April. Additionally, the zooplakton was more abundant in the open sea. It is concluded that during months of more high temperature (June to November) La Restinga lagoon notably enrich the adjacent sea and probably is one of the factors which contribute for the fertility of this area, when the upwelling effect is less intensive or disappears.