A Qualitative and Quantitative Measure of Aufwuchs Production

Aufwuchs production was measured from its accrual on plexiglass substrates submerged in a stream. A method was developed for separating autotrophic and heterotrophic aufwuchs production and for separating this production from organic and inorganic sediments. The average aufwuchs production in the entire river during the summer of 1961 was 281.8 mg organic weight M-2 day-1, with the autotrophic organisms contributing 212.8 mg and the heterotrophic 69.0 mg. The rate of accumulation of organic material on artificial substrates has been used to estimate production within streams and to estimate the well-being of natural waters. In the past these measurements have included all of the organic matter which accumulated on the substrates and little thought was given to the origin of this material. The method given here allows the separation of this material into the components that are formed on the substrates and those transported from elsewhere and deposited. The technique of collecting aufwuchs communities from natural waters by means of artificial substrates has been employed for many years in a wide variety 1 This research is part of a thesis for the degree of Ph.D. presented to the Graduate Faculty of Michigan State University by the senior author and was supported by a grant (WP-00011-06) from the National Institute of Health. 2 Present address: Department of Civil Engineering, University of Missouri, Columbia, Missouri. TRANS. AMER. MrcRosc. Soc. 85(2): 232-240. 1966. :MEASURE OF AUFWUCHS PRODUCTION 233 of ecosystems. Hentschel ( 1916) generally is credited with being the first to use this method; but Butcher (1932), Ivlev (1933) , Newcombe (1949, 1950), Patrick, et al. ( 1954), Castenholz ( 1960), Grzenda and Brehmer ( 1960), Kevern ( 1962) , Sladeckova ( 1962), Wetzel ( 1963), and many others have used artificial substrates to study aufwuchs growth, production, and succession. Cooke ( 1956) reviewed the history and general methods of collecting aufwuchs on artificial substrates. Direct microscopic examination of the exposed substrates has been used by many workers, but Newcombe ( 1949) was the first to deal with the production of total organic matter, in contrast to the earlier work that was concerned chiefly with species composition. Grzenda and Brehmer ( 1960) developed a method of estimating aufwuchs production on artificial substrates from phytopigment extracts, and our method employs an expansion and modification of their procedure. A study was conducted during the summer of 1961 on a 30-mile section of the Red Cedar River, a warm-water stream located in the south central portion of the lower peninsula of Michigan. This study was originated to determine the energy exchange in a warm-water stream, with special attention to changes in primary and secondary production with variation in stream ecology. The material presented here represents a portion of that study. This section of the river drains 355 square miles of rolling farm and suburban land and for purposes of this investigation was divided into five different ecological zones. The Red Cedar is representative of many midwestern streams in that it receives industrial and domestic wastes and inorganic sediments from agricultural areas.