Expansion of Ulva maeotica and Cladophora siwaschensis (Chlorophyta, Chlorophyceae) in the Sea of Azov and the Black Sea

The trends of changes in the spatial distribution of endemic species of macroalgae in the Sea of Azov and the Black Sea are shown using the example of Cladophora siwaschensis C. Meyer and Ulva maeotica (Proshkina-Lavrenko) P.M. Tsarenko. Currently, these algae are expanding their ranges and colonizing new biotopes in the Azov and Black Seas. From 2000-2010, U. maeotica was recorded in the area of the Kerch Strait, in the Temryuk Bay and Beysug Estuary of the Sea of Azov, in the Tsokur, Bugaz, Vityazevsky estuaries, and in the Tuzla Spit estuaries (Taman Peninsula), where it lived in a salinity up to 40% and in high-water trophicity. In the early part of 2010 the seaweed appeared near the coast of Crimea. Such rapid expansion of new biotopes by these macroalgae may be the result of climatic changes in the area of the Sea of Azov and the Black Sea, i.e., warming and reduced transparency of surface waters, and increased eutrophication in certain parts of the Black Sea coastal zone. Obviously, such changes in the marine environment are favorable for the distribution of U. maeotica and C. siwaschensis in most of the Azov and Black Sea coastal zones. Active construction and water pollution, especially in the Black Sea, can prevent these endemic species from inhabiting the estuaries. A possible way for U. maeotica and C. siwaschensis to actively expand their distribution is through the penetration into shallow saltwater coastal estuaries-lakes, where they can grow in large numbers and relatively quickly inhabit new biotopes. New findings and the distribution of endemic algae in the Sea of Azov and the Black Sea indicate that a further increase in temperature and a decrease in the transparency of sea water are optimal conditions for their distribution in most Sea of Azov, Black Sea and, probably, Mediterranean coastal waters and estuaries.