The sea of the maritime zone of Dugi Otok Island has the same or similar physical and chemical properties as the Central Adriatic parts of the sea. The average temperature is from 12°C in winter to 24°C in summer. The salinity is 38.2 ‰, and the thermocline is at a depth of 14-30 metres. Surface currents are weaker in summer and stronger in winter, within a range of 0.3 to 0.8 knots.
The predominating direction of the sea currents is from the SE direction. Sea currents, along with wind and waves, have a significant influence to the distribution of anthropogenic pollution of the sea. With its position in the E-W direction, Dugi Otok Island is located within an isobath of 100.0 m, and according to the types of benthic biocenosis, it falls into the biocenosis of coastal terrigenous muds. Its westernmost part, together with the islands, falls into the biocenosis of the open sea detritic bottom. With regard to oligotrophic waters, the sea in this area represents a very favourable ecological niche for the development of many plant and animal species whose habitats are richest in the rough and rocky bottoms.
Sea quality of the Nature Park is influenced by the growing trend of development and expansion of nautical tourism offer. In the last 15 years there has been a significant increase in docking and anchoring of boats, sailboats and motorboats. In addition to that, wastewater releases from a few restaurants and other facilities are located in the bays of the Nature Park.
In 2008, Ruđer Bošković Institute prepared the “Basic Ecological Study of Nature Park Telašćica”. The fundamental aim of the study was to determine the “zero state” of concentrations of selected macro- and microelements, and the distribution of natural and artificial 137Cs radionuclide in twenty stations in surface sediments of the seabed in the area of Telašćica. A model of acceptance capacity was created based on the aforementioned, as well as other parameters. The results of the study will be used for the advancement of the system of visits and optimum management of the Nature Park. Analyses of wastewater from the restaurants in Mir Bay are regularly conducted by the Institute of Public Health in Zadar.