Impact of Lake Acidification on Stratification

Abstract

The effects of documented acidification‐based increases in transparency, i.e., decreases in diffuse light attenuation, kd(m-1), on the occurrence and character of thermal stratification in lakes is evaluated with a mathematical mixed layer (integral energy) stratification model. Predicted changes in the character of stratification in deep lakes include: deeper epilimnia, reduced density gradients in metalimnia, increased hypolimnetic heating, and reduced stability. These changes, brought about as a result of a reduction in kd from 0.75-0.15m-1, were generally as great as or greater than those associated with extremes in meteorological conditions in a north temperate climate. The changes in stratification may have important implications with respect to the vertical cycling of dissolved constituents and the oxygen resources of hypolimnia. Model predictions indicate that lakes of maximum depth less than 25 m located in the Adirondack Region of New York State may change in character from exhibiting strong summer stratification to stratifying only weakly or not at all as a result of similar decreases in kd. Shallower lakes are more susceptible to less extreme reductions in kd. A number of lakes in the Adirondack Region have probably been eliminated as cold‐water fisheries as a result of this effect.