Relationships between dissolved organic carbon concentrations, weather, and acidification in small Boreal Shield lakes

Abstract

We used multiple linear regression analyses to explore empirical relationships between dissolved organic carbon (DOC) concentrations, weather, and acidification in long-term data sets from 12 small Boreal Shield lakes in Ontario, Canada. In two lakes in which pH changes have been very large (4.5 to ~6.0), pH explained most of the temporal variation in DOC concentrations. In the remaining lakes, long-term average previous temperature (on the scale of a decade or more) was usually the best explanatory variable for DOC concentrations. Lake-specific multiple regression models constructed from long-term and short-term attributes of weather (long-term average previous temperature and precipitation, winter–spring precipitation, summer precipitation, summer sunshine) and pH explained between 41% and 96% of the temporal variation in DOC concentrations during the entire monitoring period for these lakes (n = 16–26 years). Multiple regression models considering only the period common to all lakes, 1987 to 2003 (n = 16–17 years), explained 35%–96% of the variation in DOC concentrations. The importance of long-term and short-term attributes of weather in explaining temporal variations in DOC concentrations suggests that changes in climate will have large effects on lake clarity; however, the interactions between weather-related effects may be very complex.