Responses of northern New England lakes to atmospheric inputs of acids and heavy metals

Abstract

Ninety-four low-humic lakes in northern New England (82 in Maine) located in largely non-calcareous terrain were studied to detect possible changes in pH and associated effects. Modern colorimetric and electrode pH measurements yield equivalent results plus or minus 0.1 pH unit, permitting comparison of modern electrode pH measurements with older colorimetric measurements. Eighty-five percent of the lakes are more acidic now. Studies of present water chemistry indicate that Fe, Mn, Pb, Zn, and Al concentrations tend to be higher with decreasing pH for the set of lakes; Na, K, Ca, Mg, and alkalinity tend to be higher with increasing pH for the set of lakes. Surface sediment chemistry indicates that the concentrations of NA/sub 2/O, K/sub 2/O, MgO, and organics are highest at higher lake pH values; Cu increases with decreasing pH. The relative abundances of taxa of diatom remains in profundal surface sediments from a sub-set of 25 lakes are related to surface water pH's in the range of 4.4 to 7.0. Cladoceran stratigraphy in sediment cores from three high-altitude lakes indicates community changes concurrent with changes in diatom assemblages postulated to be caused by lake acidification. 50 references, 50 figures, 6 tables.