Organic acids, a component of dissolved organic carbon (DOC), can be a major factor in the acidity of many lakes and streams. In order to evaluate the importance of organic acidity, we fractionated (hydrophobic acids and neutrals, hydrophilic acids, bases, and neutrals) and isolated hydrophobic and hydrophilic acids from several Maine seepage and drainage lakes, and from each half of Lake Skjervatjern. For all lakes where DOC was isolated, hydrophilic acids consistently had greater exchange acidities compared to hydrophobic acids. Overall, lake DOC charge relationships and fractions were similar to forest floor DOC leachate chemistry that was also examined in detail at a site in Maine. This suggests that the nature of DOC in the temperate to boreal ecosystems studied (e.g., high carboxylic functional group content) is rather similar regardless of source (e.g., upland soil leachates, wetlands, or Sphagnum deposits).