The Northern Adriatic represents the northernmost biogeographic sector in the Mediterranean Sea. The seabed along the western Istrian coast is mostly rocky and therefore particularly suitable for the growth of brown macroalgae of the genus Cystoseira. The western coast of Istria extends for about 100 km in a north-south direction. This particular orientation affects a large variation of oceanographic variables and wave dynamics. The intertidal zone is dominated by the settlement of the species Cystoseira amentacea, whose maximum abundance is in the south of Istria. In the proposed project, we will examine the distribution and density of the settlement of the species C. amenatacea along the entire Istrian coast with special attention to determining the topography of its habitats. A general regression of species of the genus Cystoseira has been recorded on the western coast of Istria, primarily in the infralittoral zone. Before 2015, mixed communities of brown macroalgae Cystoseira compressa, Cystoseira barbata, Cystoseira crinita, Cystoseira foeniculacea and Cystoseira humilis formed rich habitats, which mainly dominated the rocky bottom. The chronology of the regression of the Cystoseira species population was monitored from spring 2015 to autumn 2018 at several stations. Based on the above mentioned observations in the proposed project we will assess the current status of Cystoseira species and possible first signs of regression of their habitats due to local and global stressors, among which we will pay more attention to monitoring the impact of increased summer temperatures, benthic blooms and sea urchins, as scavengers. Furthermore, we will examine in more detail the reproductive phenology of Cystoseira species, which is a prerequisite for their successful reproduction, growth and development, and we will also test some economically justified and effective methods for the possible restoration of some degraded habitats of Cystoseira species along the Istrian coast.