MEIOFAUNAL ABUNDANCE 201 



DISCUSSION 



It was important to collect all sites during stable, fair weather 

 undisturbed by temporary rains, winter runoff, or spring floods. The 

 three parameters in the physical— chemical index are easily changed 

 by an influx or spate of water, which would also change the observed 

 abundance of meiofaunal taxa since the sampling scheme is closely 

 tied to the water level. 



Total conductivity is a blackbox-like measure that in no way 

 specifies which ions are present, in what proportions, or involving 

 what sorts and amounts of chemical complexing. What we have done 

 in proposing the compensated noncarbonate conductivity index is to 

 exclude from consideration those ions which are measured in 

 titrating alkalinity. It can be said at present that, in the autumn 

 season under relatively stable weather conditions, the index provides 

 a relationship between certain physical— chemical parameters of the 

 streams surveyed and the number of meiofaunal taxa and geometric 

 mean abundance per station of total meiofauna and Diptera within 

 those same streams. 



Based on levels of compensated noncarbonate conductivity. Long 

 Run is more closely associated with Strouds Run and Margaret 

 Creek, the two unpolluted streams, than with Raccoon Creek and 

 Sandy Run upper, the two polluted streams. On the other hand, both 

 sites on Long Run have fewer than the expected number of taxa, and 

 the lower site has greater than expected abundance of total 

 meiofauna. Tick Ridge upper is most closely associated with the 

 polluted streams, although it has a greater than expected number of 

 taxa and total meiofaunal abundance and no observed Diptera. 

 Minkers Run, Tick Ridge lower, and Sandy Run lower occupy 

 intermediate positions, with the Sandy Run site having fewer than 

 the expected number of taxa and both the lower sites at Minkers and 

 Sandy Runs having greater than expected abundances of total 

 meiofauna. 



Results of the similarity analysis form a pattern, not greatly at 

 variance with results of the correlation analysis. Long Run again is 

 more closely associated with the unpolluted than with the polluted 

 streams, with Minkers upper and Tick lower occupying comparable 

 positions. Raccoon Creek and Sandy upper, along with Tick upper, 

 are located at the ends of the array, but joining them in this case are 

 Sandy lower and Minkers lower. 



On balance, considering Strouds Run and Margaret Creek to be 

 unpolluted and Raccoon Creek and Sandy upper to be polluted, the 

 following comments on the other seven sites can be made. The Long 



