INTRODUCTION

Baikal is the largest lake in the world, containing one-fifth of the world’s store of surface fresh waters or half of the available drinkable water. The ecosystem of the lake has several unique features, which make the lake a notable natural phenomenon. It is the oldest and the deepest freshwater lake in the world, the only, among large lakes, where the water is saturated with oxygen to the maximum depth. Lake Baikal is a unique natural laboratory, from which we can study the origin, evolution of biodiversity, nonmixing of endemic and widely spread species complexes, and many problems of ecology, lake science, and other sciences. Nature has provided us with such great resource as lake Baikal to solve important tasks such as the problem of pure water and of global climate change.

Problem of Pure Fresh Water

From the point of view of the problem of pure fresh water lake Baikal is interesting in two aspects. First, it is interesting as a giant reservoir of fresh water. Lake Baikal is equal by volume (23,000 km3) to all the great Laurentian lakes together, while the purity of its water is incomparable with that of the American lakes, as they have not yet recovered after the catastrophes of 1960s and 1970s. Second, lake Baikal is not only a reservoir but is also a giant factory of pure drinkable water of the highest quality under natural conditions, as the functioning of the ecological system of the lake provides water of high quality.

Problem of the Global Climate Change

Baikal must be studied from this perspective as its great size makes it a very conservative system, changing very slowly. At the same time, these changes, if begun are irreversible. It

is necessary to look at the possible deviations of the ecosystem functioning from normal ones. The influence of global warming on some parameters of the ecosystem state of lake Baikal was studied by some authors.[1–4] Recent study by researchers at the Institute of Biology, Irkutsk State University carried out in collaboration with German, Czech, and U.S. scientists[5–14] demonstrates the average increase in the temperature of water by 18C for a year at the surface since 1946 and by 0.28C at a depth of 50 m. A sufficient increase of biomass of summer phytoplankton is registered, and there are some changes in the zooplankton composition.

This is the reason why an in-depth knowledge on the manner we study the ecosystem of the lake is necessary. Most detailed works on this subject were published decades ago.[15–25] The most interesting is the simplicity of the main ecosystem of the pelagic part of lake Baikal, providing the functioning of the ecosystem.[20–24] It consists of several species of algae (,10–15), super-dominant species of zooplankton Epischura baikalensis, accompanied by minor species of Cyclops kolensis, rotifers and cladoceran, one species of predatory zooplankton Macrohectopus, two species of Comephorid fishes, one species of seal:

Algae-Epischura-Macrohectopus-Comephorids-Seal

Recent reviews mainly correspond to materials of the state reports,[26–33] and hence does not dramatize the situation. They deal with physical and biological impact on the lake, while chemical pollution of the lake is described in another entry of this encyclopedia. Among various other impacts chemical pollution of lake Baikal is one of the most important part of the anthropogenic impacts on the lake. However, it is necessary to remember that although there is some contamination in the lake, nevertheless, the water of lake Baikal remains the most pure among the natural lake waters and is potable even in the regions of local pollution.