Meiofauna of the profundal zone of the northern part of Lake Ladoga as an indicator of pollution

The meiofauna of Ladoga lake was compared with that of smaller lakes, particularly Paijanne lake in Finland, to determine the comparative pollution situation in Ladoga lake. Benthic meiofauna was sampled at 19 stations, mostly in the northern part of the lake, at depths from 13 to 199 m and in a range of different types of environment. Certain quantitative ratios of meiofauna were correlated with environmental data. Most oligochaetes and harpacticoids were confined to the less eutrophic environments, though some species were concentrated in the more eutrophic or polluted areas. In general, pollution tolerance was high, probably due to the effective mixing of large water masses.