Algae Caulerpa cylindracea Sonder is organism of tropical and moderately warm seas widespread around the world. Invasive variety of this algae is growing from surface to 50 m of depth, at all types of marine benthic habitat in the polluted and clean seas as well. In the Mediterranean Sea was first found in 1926. in Tunisia and is considered to belong to a group of lesepian species. Field research was conducted at the National Park "Mljet" at 8 stations. In the area of NP Mljet in the all research stations, strong hydrodynamism has been noticed, which is why the breaking and dispersion of algae particles by sea currents is the most common way of spreading it. The measurements of the alga C. cylindracea cauloide growth were carried out in summer and fall months. The measured annual growth of C. cylindracea algae averaged 10.1 millimetres per day at all research stations, and the maximum average algae growth measured at the Veliko jezero station was 15.6 mm per day. The growth rate of the algae C. cylindracea thallus is in a positive correlation with the higher summer temperature of the sea. The amount of light has a lower impact on growth than the higher sea temperature. Algae growth at 40 and more meters of depth in the Adriatic Sea, and the size of its habitats confirms the thesis that this green algae does not need much light for its growth. Benthic sessile organisms, such as algae, sponges, corals, polychaetes and bryozoans, are the most endangered by the extinction of their habitats by invasive algae C. cylindracea. Meadows of seagrass P. oceanica stops spreading invasive algae, and alga grows only on damaged parts of the meadow. During the research at any stations, no feeding of sea urchins with invasive algae was found, while the fish from the Sparidae family by feeding are likely to increase the spread of algae rather than help eradicate the invasive algae. The best way to clean the invasive C. cylindracea algae was to clean it manually. Mamuth pump and black foil cover negatively affects benthic organisms.