CHEMICAL, BIOLOGICAL AND SOCIOECONOMIC APPROACHES TO THE LIMING OF LAKE-ALINENJARVI IN SOUTHERN FINLAND

The aim of this comprehensive study is to estimate the effects and use fulness of liming Lake Alinergarvi based on chemical, biological and s ocio-economic studies. Methodological standpoints concerning the limes tone dissolution rate, acidic surges and reacidification are also disc ussed. L Alinenjarvi (0.45 km(2)) is located near the city of Nokia wi th a surrounding population of over 5 000 (< 2 km). Before liming,the lake had only a sparse crayfish (Astacus astacus L) population left, b ecause reproduction had been failing since the early 1980s. The most i mportant effect of liming is that it should connect with the potential production of crayfish. The roach (Rutilus rutilus L) population was also affected The liming improved the chemical quality of the water, a nd decreased also the Al and Mn concentrations. The number of phytopla nkton species increased, and the species composition of periphyton cha nged after liming. The a-chlorophyll concentration in water remained l ow. Furthermore, crustacean zooplankton and benthic animals increased in abundance in the first late summer after liming. ?he diet analysis of perch (Perca fluviatilis L) gave comparable results suggesting a po ssible positive effect of liming on their food resources. The improved water quality seems to make the reproduction of the crayfish possible again, but recovery would take several years. To guarantee a recovery , the introduction of new crayfish individuals and supplementary neutr alizing methods would be needed. The results of a mailed survey showed that L Alinenjarvi is a valuable water source for the local people. T he most usual forms of leisure around the lake and shores are, however , outdoor recreation and swimming, with only minor usage for fishing. Despite that, though the immediate benefits would be negligible, a maj ority of local residents supported the continuation of liming even tho ugh they would have to carry the costs in the future.