SUMMARY 



Composite periphyton samples were collected at five sites on 

 Big Spring Creek in August 1998. Samples were collected at two 

 sites in the B-1 section of the stream above Lewistown and at 

 three sites in the B-2 section below Lewistown. The samples were 

 analyzed using standard methods for the rapid bioassessment of 

 stream periphyton. 



Big Spring Creek above Lewistown had a non-diatom flora 

 consisting of the blue-green alga Phormidiuin, plus mosses and 

 aquatic macrophytes . This flora is typical of spring creeks with 

 a steady flow of cold water. 



Green algae appeared at the Carroll Trail site and were 

 abundant from there downstream. Organic enrichment was indicated 

 by the appearance of SCigeoclonium at Carroll Trail and dominance 

 by this alga at the Spring Creek Colony. Cladophora was also 

 very abundant at the three downstream stations. 



Dominance by Cocconeis placentula below the hatchery was 



related to the abundance of aquatic macrophytes at this site. 

 Diatom metrics indicated that this site had excellent water 

 quality in all other respects. 



Diatom species composition indicated minor siltation and 

 nutrient enrichment below Lewistown, but full support of aquatic 

 life uses. A moderate change in species composition between the 

 control (hatchery) site and Burleigh's Easement indicated that a 

 significant change occurred in this reach. The nature of this 

 change is unclear, but may be related to natural marl {calcium 

 carbonate) deposits on the stream bottom. 



Carroll Trail, Spring Creek Colony, and the site near the 



mouth all had somewhat dissimilar diatom floras when compared to 

 the control site below the hatchery, but this is to be expected 

 given the distance downstream, intervening tributaries, and the 

 change in stream classification. Minor changes in the diatom 

 flora were noted between Burleigh's Easement and Carroll Trail, 

 and between Carroll Trail and Spring Creek Colony. The diatom 

 flora near the mouth of Big Spring Creek was not measurably 

 different from the flora at Spring Creek Colony, indicating no 

 additional sources of impairment in this reach. 



Diatom metrics indicated full support of aquatic life uses 

 at all five sites sampled on Big Spring Creek, with no man-made 

 impairment at the two upstream sites and only minor impairment at 

 the three downstream sites . 



