Partitioning Light Attenuation in an Acidic Lake

Abstract

Although a number of researchers have reported that acidification of lakes is accompanied by an increase in transparency, there has been no systematic evaluation of the processes responsible for this transformation. In this study we partitioned the attenuation of light in acidic Dart's Lake, located in the Adirondack region of New York from May to September 1982. We observed that changes in light attenuation (Kd) and light absorption (a) were regulated largely by "gelbstoff." Substantial decreases in Kd and a occurred through the study period and were correlated with a depletion in the concentration of dissolved organic carbon (DOC). In-lake concentrations of DOC were controlled by terrigeneous loading and in-lake processes. The decrease in DOC and the attendant decreases in a and Kd were coupled to a loss of Al from the water column of the lake. We suggest that coagulation/adsorption of DOC by Al may have contributed to increases in lake clarity. Increased transparency is significant because it enhances hypolimnetic heating and decreases the thermal stability of lakes.