The Invasion of the Alien Species Bonnemaisonia hamifera Hariot in Coastal Phytocenoses Near the Southern Coast of Crimea (the Black Sea)

Based on the results of hydrobotanical research in 2015–2021, it has been found that the global expansion of the Bonnemaisonia hamifera Hariot filamentous sporophyte stage had reached the Southern Coast of Crimea (SCC) by 2017. At present, the invader is registered in all horizons of the SCC phytal. Massively developing in the epiphyton of native species, it inhibits their growth, and in some areas it becomes one of the dominants. This changes the appearance, structure, and production indicators of algal communities (up to their degradation in some areas), which makes it possible to attribute this invasive species to the “transformers” category. It has been shown that the invasion develops rapidly, its vector coincides with the direction of the Main Black Sea Current. Eutrophication can play a stimulating role. Presumably, the species is already present on the southwestern and western coasts of the Crimean Peninsula and will populate the western and northwestern regions of the Black Sea in the next one or two years; expansion into the Sea of Azov is also likely. B. hamifera invasion may threaten biological diversity of the of the entire Azov-Black Sea basin, which under the conditions of its relative isolation can lead to ecological catastrophe that will affect all countries in the region. Currently, there are no ways that could stop or slow down the process of invasion.