sampled on May 25 bracket the City of Lewistown (Map 1, Table 1) . 

 The four sites sampled in August span the reach from just below 

 Big Springs to near the mouth of the stream (Maps 2 and 3, Table 

 1) . Elevations at the sampling sites range from 4250 feet below 

 Big Springs to 3475 feet near the mouth of the creek. 



Recreation, fish and aquatic life uses in upper Big Spring 

 Creek are threatened by land development and discharges from a 

 fish hatchery (MDEQ 1998) . Below Lewistown, aquatic life, fish 

 and recreational uses are partially impaired by agriculture, 

 channelization, on-site domestic wastewater, the outfall from the 

 Lewistown wastewater treatment plant, stormwater runoff, animal 

 confinement facilities, and silviculture (MDEQ 1998). 



Three previous reports on Big Spring Creek and tributaries 

 have been prepared for MDEQ by this consultant (Bahls 1999a, 

 1999b, and 2001) . 



METHODS 



Periphyton samples were collected in May by Tom Pick, 

 NRCS/DNRC, and in August by Rebecca Ridenour, MDEQ Monitoring and 

 Data Management Bureau, following standard operating procedures 

 of the MDEQ Planning, Prevention, and Assistance Division. 



Using appropriate tools, microalgae were scraped, brushed, 

 or sucked from natural substrates in proportion to the rank of 

 those substrates at the study site. Macroalgae were picked by 

 hand in proportion to their abundance at the site. All 

 collections of microalgae and macroalgae were pooled into a 

 common container and preserved with Lugol ' s solution. 



The samples were examined to estimate the relative abundance 

 and rank by biovolume of diatoms and genera of soft (non-diatom) 



