Effects on the aquatic biota of lime (CaCO 3 ) application in acidified lakes and streams were studied in a number of waters . After treatment, lime-sensitive species of mosses (Sphagnum spp .) decreased, but species such as Potamogeton natans and Myriophyllum alterniflorum seemed to be favoured . A few years after liming species composition and diversity of phytoplankton, zooplankton and benthic insect larvae were almost identical to that found in oligotrophic and non-acid lakes . Molluscs and benthic crustaceans may have difficulties recolonizing . Reproduction of remaining species of fish was successful as soon as pH increased . High survival of larvae and fry can result in some extremely rich year classes with slow individual growth . In most cases restocking of depleted fish stocks was successful .

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Increases in pH from 4.5–5.3 to 7–7.6 after liming (1978–85) in six acidified lakes in the west coast area of Sweden caused increased concentration of humic compounds and decreased transparency compared with levels before liming. Concentrations of total P increased markedly whereas those of NO3-N decreased. The phytoplankton composition changed completely in all lakes shortly after liming, but a species richness similar to that in unacidified lakes was not reached until after 2–5 yr, and in the previously most acidified lakes, several species remained absent. The composition of the phytoplankton indicated increased primary production. The volumetric dominance within the zooplankton shifted generally from Eudiaptomus–Holopedium to Cyclops–Daphnia. The occurrence of Rotatoria and Cladocera species increased and the composition became similar to that in unacidified lakes 2–5 yr after liming. The biotic development is largely explained by chemical–physical changes such as increased pH, reduced Al concentration, increased P concentration, and increased organic content, particularly humus.

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