A comparative study of the Williamson River (before and after passage through Klamath Marsh) and the Sprague River (which is a major tributary of the Williamson River) in South Central Oregon has provided substantial insight into the effects of a marsh environment on the transport of iron and aquatic humus in river water. In the Sprague River and in the pre-marsh Williamson River, iron is transported primarily as 0.80 ym suspended particulate material. In Klamath Marsh, this coarse particulate material is "weathered11, yielding iron-aquatic humus "complexes'1. Thus, most iron and aquatic humus in the post-marsh Williamson River are in the 0.025 ?m size fraction. Presumably, other trace metals would be similarly affected. Klamath Marsh serves as an important source of biologically derived solutes such as amino acids and sugars. Fractionation studies have shown that amino acids are almost exclusively humic-bound in the Will-iamson River system, while sugars may be present as either polysacchar-ides (PS) or humic-bound saccharides (HS). The PS/HS ratio may reflect the relative importance of autochthonous and allochthonous sources of sugars. Major solute composition strongly indicates that ground waters flowing into the pre-marsh Williamson River and the Sprague River are derived from a different source than are ground waters which enter the post-marsh Williamson River from Big Springs, Spring Creek, and from unidentified springs below Klamath Marsh. Nutrient concentrations (H4SiO4, NO3, PO43) are significantly higher in spring waters than elsewhere in the system. While nitrate levels (3-11 ?m) were somewhat low, phosphate levels (1-3 ?m) were quite high throughout the Williamson River system. There was some evidence for nitrogen limitation of algal growth in the pre-marsh Williamson River. While Fragilaria construens was dominant throughout the Williamson River system, several Navicula spp. were restricted to the pre-marsh Williamson River and several Fragilaria spp. and Nitzschia, spp. were found only in the post-marsh Williamson River. In Upper Klamath Lake, Stephanodiscus astrea minuta, Fragilaria construens, and Aphanizomenon flos-aquae appeared in succession, with nuisance blooms of the latter organism occurring July-November. The cessation of flow of humic-rich water from Klamath Marsh during the summer months drastically decreased the flux of aquatic humus, iron, amino acids, and other marsh-derived solutes in the post-marsh Williamson River. At the time of cessation of flow from Klamath Marsh, nuisance blooms of Aphanizomenon flos-aquae appeared in Upper Klamath Lake. Furthermore, when flow from the marsh was re-established with the first major winter rains in November or December, Aphanizomenon flos-aquae abruptly ceased to grow in Upper Klamath Lake. Further studies are planned to determine whether this correlation is causal or coincidental.
Completion report for Project A-047-ORE, Office of Water Research and Technology, United States Department of the Interior