to provide time for the chlorophyll and other pigments to leach into the 

 acetone. Previous work has shown that 90% of the periphytic pigments are 

 leached into solution after 20 to 24 hours (Weber et al 1980). Next, an 

 aliquot of the acetone was transferred to a curette and absorbance was 

 measured using a Bausch and Lomb Spectronic 70 Spectrophotometer. Finally, 

 surface area of the rocks was estimated by the method of Kaiser et al (1977), 

 and periphyton standing crop was estimated via the chlorophyll levels accord- 

 ing to the chromatic equations that are presented in Weber et al (1980). 



Chlorophyll Results 



In general, there was good agreement between replicates from all three 

 locations (Table 14). The stream reach below Beef straight Creek appears to be 

 less productive than either of the other two sampling locations. Greatest 

 production of periphytic biomass occurred near the mouth. 



Periphyton productivity of German Gulch Creek is relatively high compared 

 to other Montana streams (Ingman et al 1979, Bahls et al 1981), and was in a 

 range similar to that reported for the Yellowstone River near Billings 



(Klarich 1976). Estimated average standing crop of chlorophyll for Montana 



2 

 waters (assuming an asymptote at 35 days) is 1 . 7 ug Chi a/cm . Periphyton 



2 

 standing crops in German Gulch below Edward Creek (3.19 ug CHI a/cm ) and near 



2 

 the mouth (4.16 ug Chi a/cm ) were well above this average. Nitrogen 



compounds measured during the water monitoring were present at very low 



concentrations. Perhaps German Gulch Creek is nitrogen limited. 



-14- 



