Acidification of Lake Annie,Highlands Co., FL

Lake Annie, a clear-water seepage lake in south-central Florida remote from significant pollution sources, was sampled by the USGS from 1966 until 1978, and by Battoe and others from 1978 until present. Since 1966, pH and bicarbonate alkalinity have decreased (pH from above 6.0 to about 5.1; bicarbonate from 5.0 to less than 0.5 mg L^?1), while specific conductivity and sulfate concentration have increased (cond. from 30 to 55 μS; sulfate from 3.0 to 8.0 mg L^?1). The chemical changes are apparently due to acidification from atmospheric deposition. There are no proximate sources of acidity and the stability of lake level indicates there has been no significant concentration or dilution of solutes. It is suggested that Lake Annie's acidification was a threshold phenomenon wherein, following depletion of the watershed's buffering capacity, acidification of the lake was rapid.