Hydrologic control of dissolved organic matter in low-order Precambrian Shield lakes

Concentrations of dissolved organic carbon (DOC) and color were measuredas a function of time in enclosures and lakes at the Experimental Lakes Area,to calculate their net loss rates. Loss rates in enclosures werefirst order for both DOC and color, with half-times for loss of 166and 122 d, respectively. Thus, the colored, light-attenuating componentof the DOC pool is lost from water more rapidly than is bulk DOC. Loss ratesin lakes, calculated from a steady state model, were similar to values forcolor in enclosures, but for DOC in lakes were four times slower than inenclosures. In lakes, loss rate for DOC increased rapidly with decreasingwater residence time (_w) but was independent of_w when it was greater than 3 years. In lakes, theloss rate for color was independent of water residence time. Thedifference in losses of DOC and color between lakes and enclosurescould be from release of low-color DOC from sediments.