The ISO-ZOKO project, as an extended continuation of the MARRES project, aims to investigate the variability of stable isotope signatures (13C, 15N, 34S) and C/N/S ratios of organic matter (OM) in different water layers of the Rogoznica Lake (RL) - Zmajevo oko marine system, with special focus on the hypooxygenated epilimnion and the euxinic chemocline and monimolimnion. Stable isotopes will be studied together with other relevant proxies as indicators of the origin and fate of OM with respect to the physico-chemical stability of the RL water column and possible wet and dry inputs from precipitation, pollen, surface runoff and karst groundwater. The main objective is to distinguish between different allochthonous and autochthonous sources and characteristics of OM in this highly stratified marine environment. An important goal, but also the outcome of this project, is the installation of a permanent station for continuous monitoring of the physico-chemical parameters (T, S, O2, pH) with high spatial and temporal resolution in the centre, above the deepest point of the lake. The measuring station will be an important data source for monitoring subtle changes in the stratification of the water column not only within this project, but also in the future for all those interested in limnological and/or research on changing environmental conditions. Such research in times of intense climatic and ecological change has a very important local but also broader scientific impact.The project results will contribute significantly to the knowledge of the sources, fate and cycling of OM in coastal environments such as shallow bays, lagoons and marine lakes, as well as to the systematic monitoring, sustainable use, protection and management of RL and similar marine systems. An important contribution is seen in the strengthening of research capacity and collaboration within the complementary and interdisciplinary research group, including the training of young researchers.