This chapter describes the influence of heavy metals on hydrobionts, presenting
generalized information on heavy metal distribution in the atmosphere, atmospheric
precipitation, bottom sediments of rivers and lakes of different regions of the world.
Data on metal concentrations in water of a number of water bodies in Russia are
compared, and some water quality criteria for heavy metals in different countries are
discussed. Special attention is given to the danger of mercury. It is shown that the most
globally widespread organic pollutants are oil and oil products, chlorinated organic
hydrocarbons and polycyclic aromatic hydrocarbons. The highest levels of hydrocarbon
content are typical for inland seas as well as for near-coastal, and shelf zones, and for
seas where oil production and transportation are carried out. A general scheme is
presented for development of biologic effects of oil pollution, including acute and
chronic impact on hydrobionts. It is noted that chlorinated hydrocarbons, as well as oil
products and heavy metals, have become toxicants of global abundance.