Veruchev also noted that a period when uranium accumulated was always distinguished by particularly active development of plankton. We now know that radioactive nuclides are quickly absorbed into living tissue, at varying rates depending on the organism and its developmental stage. Therefore, phytoplankton function as the most effective, ecologically important filter for the region, capable of removing excessive uranium and other harmful elements in a matter of hours or days. In this way, phytoplankton protect the rest of the ecosystem from radioactive nuclides and other toxic substances by absorbing the first blow. A second line of defense is created by larvae, the fry of fish, tadpoles, insects, and others.
Mature fish represent the third line of defense against radiation.
Their gills, where radioactive nuclides, heavy metals, and other toxic substances can accumulate, are powerful filters. However, fish can only absorb a limited amount of radioactive nuclides before a decline of the ecosystem occurs. In this regard, it is worrisome that after a powerful atmospheric nuclear weapons test in 1962, the total biomass of phytoplankton in the Caspian Sea at first sharply increased and then bore a sharp decline by 1974. We must work to preserve the natural radiation defense system in the Caspian Basin ecosystem by establishing NGOs as a new line of defense. There are two fundamental tasks.