American Fisheries Society Symposium 47:239–262, 2005 Assessing Water Source and Channel Type as Factors

Abstract.—The Santa Ana River basin is the largest stream system in Southern California and includes a densely populated coastal area. Extensive urbanization has altered the geomorphology and hydrology of the streams, adversely affecting aquatic communities. We studied macroinvertebrate and periphyton assemblages in relation to two categorical features of the highly engineered hydrologic system—water source and channel type. Four water sources were identified—natural, urban-impacted groundwater, urban runoff, and treated wastewater. Three channel types were identified—natural, channelized with natural bottom, and concrete-lined. Nineteen sites, covering the range of these two categorical fea-tures, were sampled in summer 2000. To minimize the effects of different substrate types among sites, artificial substrates were used for assessing macroinvertebrate and periphyton assemblages. Physical and chemical variables and metrics calculated from macroinvertebrate and periphyton assemblage data were compared among water sources and channel types using analysis of variance and multiple com-parison tests. Macroinvertebrate metrics exhibiting significant (P < 0.05) differences between water sources included taxa and Ephemeroptera-Plecoptera-Trichoptera richness, relative richness and abun-dance of nonchironomid dipterans, orthoclads, oligochaetes, and some functional-feeding groups such as parasites and shredders. Periphyton metrics showing significant differences between water source