the aggregate of plants that inhabit rivers, lakes, and other freshwaters. Freshwater flora includes more than 50 percent of algae species (only brown and red algae are almost exclusively marine), a small percentage of fungus and lichen species, and a substantial number of mosses, ferns, and angiospermous plants. A characteristic feature of freshwater flora is the adaptation to life in water containing a small quantity of salt (up to 0.03 percent or, less frequently, 0.05 percent). Some of the plants can live in water of varying degrees of salinity. The role of freshwater flora in nature and in the national economy is very great. Photosynthesizing plants serve as a primary link in the food chains of all aquatic organisms; for example, microscopic algae serve as food for small aquatic animals. Moreover, the plants play a major role in the self-purification of water.
Excessive growth of freshwater flora can be harmful. For example, overgrowth in reservoirs and canals hinders the operation of hydrotechnical structures. Water bloom—the coloration of water as a result of massive development of microscopic, mainly blue-green, algae—causes destruction of fishes, disables water-pipe filters, and affects the taste of water. Hundreds of grams of algae may be found per sq m.
REFERENCESVoronikhin, N. N. Rastitel’nyi mir kontinental’nykh vodoemov. Moscow-Leningrad, 1953.
Zhizn’ presnykh vod SSSR, vols. 2–4. [Part 1.] Moscow-Leningrad, 1949–56.
Lipin, A. N. Presnye vody i ikh zhizn’, 3rd ed. Moscow, 1950.
IU. E. PETROV