In the last two decades, during the summer season, mass mortalities of sessile species have occurred in the Mediterranean Sea due to the influence of increased sea temperature (positive temperature anomalies) down to 50 meters depth. These disturbances cause severe consequences for the sustainability of populations due to their longevity (they can be up to a hundred years old) and slow population dynamics. The research was conducted at 6 stations within the Brijuni National Park during autumn 2022. 34 species of corals were found at the research stations, which is 29.3% of the species found in the Adriatic Sea. The most species of corals in NP Brijuni were found at stations Vrsar (26 species of corals) and Peneda (25 species of corals). Sea surface temperature values in 2022 were slightly lower (up to 27.7°C) than in previous years when sea temperatures reached up to 30°C. In the case of the species Balanophyllia europaea, Cladocora caespitosa, Leptopsammia pruvoti and Parazoanthus axinellae, during the research, an increasingly negative influence of increased sea temperature through necrosis of polyp tissue and increased mortality of individuals and colonies was determined. At all investigated stations, an increase in the biomass of planktonic and benthic algae, as well as the formation of mucus, which have a negative effect on coral populations, was determined. The brown alga Acinetospora crinita covers the seabed at all investigated stations. During the research of corals in NP Brijuni, a wide distribution of the invasive alga Caulerpa cylindracea Sonder was found at all researched stations. Although left fishing tools were found at the researched stations, these tools are not the cause of any major threats to benthic species. Protected areas justify their purpose in the Adriatic Sea through reduced negative anthropogenic influence, which is evident in the results of this work.