780 BRADT 



(station 2) may also contribute to the alkalinity. The increase in pH 

 observed as streams flow over limestone areas is accompanied by an 

 increase in alkalinity (Reid, 1961). Hynes (1969) states that the 

 lower reaches of a stream are richer in dissolved nutrients and 

 suspended solids, and this is reflected in the downstream rise in 

 conductivity. 



Hynes (1970) suggests that nitrate concentration usually de- 

 clines downstream as the nutrient is utilized, but nitrate may increase 

 if additions from the surrounding land exceed use by the stream 

 biota. Minckley (1963) also noted a decrease in nitrate downstream. 

 Nitrate, in this study, was highest in downstream suburban and urban 

 areas (stations 10 and 2). Likens and Bormann (1974), however, 

 report that nitrate concentrations are related to the amount of 

 agricultural activity in the drainage basin. Possible sources of nitrate 

 in the downstream area are effluents from the sewage-treatment 

 plants and the limestone springs. Soil percolates may contain more 

 nitrate than surface runoff (Bigga and Corey, 1969). 



Minckley (1963) recorded a slight, but consistent, decrease in 

 orthophosphate downstream. The slight increase noted in orthophos- 

 phate downstream in this study may be due (1) to orthophosphate 

 concentrations being higher in runoff from urban areas than from 

 rural areas (Owen and Johnson, 1966; Hynes, 1970) and (2) to 

 sewage-plant effluents. 



Potential sources of chloride in the stream are minerals in the 

 drainage basin, human or animal sewage, and certain industrial 

 effluents (McKee and Wolf, 1963). The higher mean chloride at 

 station 13 may reflect the effect of the sewage-plant effluent. 



The higher iron concentrations at station 2 reflect the influence 

 of the pigment manufacturer and may also result from land runoff 

 and limestone springs (Minckley, 1963). 



The plant nutrients, nitrate and orthophosphate, contribute to 

 increased productivity in the stream. Two sewage plants, land runoff, 

 and subterranean drainage probably are the major sources of these 

 nutrients. Algal growths are common in the stream, with diatoms 

 (Chrysophyta) predominating in the winter and Cladophora (Chloro- 

 phyta) and Oscillatoria (Cyanophyta) predominating in the summer 

 (Bradt, 1974). Cladophora and Oscillatoria are often seen in enriched 

 streams with a high biomass (Hynes, 1969). 



The high percentages of the families Hydropsychidae and 

 Chironomidae (Table 2) at Station 12, 10, and 2 parallel the lower 

 diversity at these stations. Members of these two families are 

 ubiquitous and apparently able to cope with the higher nutrient 

 loads in the downstream sections. Hydropsy che is an omnivorous net 



