Relationship between microbial activity of stream sediments, determined by three different methods, and abiotic variables.

Microbial activity of stream sediments has been determined by three distinct methods: phosphatase levels, maximum uptake velocity of radiolabeled glucose, and carbon dioxide production rates. These methods have been applied to different types of sediment (mud, sand, gravel) from the same stream and to 5 samples from two different streams for comparison. Temperature, discharge, and 8 other abiotic variables for each sample were also determined. The 3 activity methods correlated closely with each other and were measured with a similar precision. Phosphatase activity could be predicted for all sites from bulk density. The largest proportion of the variance associated with carbon dioxide production was explained by variations in percent of organic matter, but the relationship did not hold for all streams. Maximum uptake velocity, compared with the other 2 activity measurements, was poorly explained by any of the abiotic variables.