FLUCTUATION OF SALINE / HYPERSALINE LAKE ECOSYSTEMS BETWEEN ALTERNATIVE STATES AND SUSTAINABLE AQUACULTURE IN THE ARID AND SEMI-ARID AREAS

Introduction of aquaculture should proceed in the context of regional sustainable development. This is especially important in arid and semi-arid regions, where the environment is highly variable, and conflicts between the different users of natural resources  easy  arise. Such conflicts are especially acute when using fresh water, which is always in short supply. Development of aquaculture in saline/hypersaline lakes  without compromising the supply of drinking water can partly avoid the freshwater use conflicts. Such aquaculture must be profitable and sustainable. To be so its development needs to be based on sound scientific background and take into account individual peculiarities of water bodies.

РисунокWhat concept is better to  manage aquaculture development in saline lakes? In general ecology, there is the traditional view on ecosystem being in a quasi-stable equilibrium, fluctuating around a single global equilibrium point, and smooth changes prevail in its dynamics. However, all real ecosystems have several alternative stable states and may demonstrate a regime shift, which is a abrupt, persistent large change in the structure and functioning of them. Every ecosystem may realizes a smooth adaptation to environmental changes if they are within an existing norm of reaction. If changes exceed this norm, destabilization of an ecosystem occurs and its transit into a new state (Fig.). In an extreme and highly changeable environment of arid areas, lake ecosystems  are more responsive to climate changes and anthropogenic impacts; different alternative stable states may be separated more easily. Own data of long-term study on hypersaline lakes in arid Crimea (Russia) helped us identify several alternative stable states in the dynamics of their ecosystems. Similar alternative states were also found in the Australian saline lakes. Transiting from one state to another, lakes/lagoons/ponds shift from one potential of aquaculture development to a different one. Different ecosystem stable states generate different resource potential and various possibilities for their  use by humans. An example of the Crimean saline/hypersaline lakes show that  humans may use filamentous green algae Cladophora and the crustacean Artemia during one ecosystem state, but in other years, they may harvest amphipod crustaceans and grow fish. Long-term sustainable use of saline lakes requires a diversity of alternative strategies of aquaculture development, and timely switch from one strategy to the alternative.

This study was supported by the Russian Science Foundation (grant 18-16-00001).