Transport of dissolved organic carbon in streams of differing physiographic characteristics

Abstract

Transport of dissolved organic carbon (DOC) in four river systems in different physiographic regions of the United States was related to link magnitude by a power function, log Y = −0.84 + 1.24 log X. Multiple linear regression indicated that discharge, watershed area, and link magnitude explained almost all variation in DOC transport. For purposes of ecosystem comparison, link magnitude appeared superior to other classification systems, such as stream order. In two of the river systems, the largest fraction of DOC was transported in the spring. A third has a winter transport maximum; the last had bimodal spring and fall maxima. Streams transporting similar total amounts of DOC may vary widely in DOC concentration (mg. 1 −1). Particulate organic matter concentration was not simply related to that of DOC. Ranges and means of DOC concentration, mean DOC: POC ratios, annual load of transported DOC as well as annual watershed DOC output were tabulated for 45 streams and rivers, representing a broad range of stream systems and physiographic regions. Mean DOC concentration for these 45 waterways ranged from 0.7 to 28 mg. 1 −1. The very low DOC values are found in undisturbed streams; many of the higher values are associated with larger streams influenced by human activities. Most DOC outputs fell within the range 0.21–5.42 metric tons. km −2.yr −1; mean DOC:POC ranged between 0.09 and 70. A comparison was made among several biomes of the ratio of experted DOC to watershed gross and net primary production. DOC, while playing a major role in aquatic ecosystem organic budgets, appears to be of little significance in the nutrient balance of watersheds.