In this study, the influence of waste waters on the coastal environment of Rovinj aquatorium used for recreational and touristic activities was estimated. For that purpose, a characterization of the organic matter and the speed of its dissolution was conducted. Concentration of the particulate organic matter during the actual release was significantly higher than those at the control station and more than usual for Rovinj aquatorium. Increased values of enzymatic activities and a relatively fast time of the dissolution stopped the amounting of the inserted organic matter in the water column of that area. Increased enzyimatic activities are detected on the its release area. During the summer, these values at the area are much higher, but enzymatic dissolution of organic matter is important even during the winter. Time of the organic matter dissolution via extracellular enzymes was the shortest in the vicinity of the release. Highest enzymatic activity and the shortest time of the dissolution was recorded at the release area of factory „Mirna“. During the winter, enzymatic activities are significantly lower than those during the summer which is partially a consequence of significantly lower temperatures, and partially because of the division of the organic matter through the water column mixing. Part of the particulate matter sedimentates which increase the amount of the organic matter in the sediment.