Enzyme activity in hyporheic soils of Piedmont streams

Background/Question/Methods

Streams and rivers are the source of our drinking water, scenic beauty, recreational opportunities and wildlife habitat. Land use practices such as agriculture, urbanization and development have caused erosion and habitat loss to some Piedmont streams, with about 10% of NC streams considered impaired. Assessment criteria of stream health generally are based on water quality, bank geomorphology and biological assessments of fish and macroinvertebrates. The goal of this research was to establish biochemical and microbial baseline measurements that could be used as assessment tools in the evaluation of stream restoration initiatives. Hyporhic soils are ecologically important as zones of active exchange between terrestrial and aquatic ecosystems.  Five major soil enzymes involved in nutrient cycling within soil were examined using methods modified for hyporheic soils. All assays were done on freshly collected soil cores.  Streams were first to third order streams. Enzymes studied included phenol oxidase, protease, acid phosphatase, β-glucosidase, and β-galactosidase.

Results/Conclusions

Results from soils collected from 16 sites during the summer of 2010  indicated a correlation between degree of erosion—determined by bank height—and enzyme activity for phenol oxidase, acid phosphatase, β-glucosidase, and β-galactosidase (R values ranged from 0.3 to 0.6).  Bank height ranging from 15 to 244 cm was used as a measure of erosion. There was also a significant effect for depth with greater enzyme activity in surface soils than at 20 cm for acid phosphatase and protease.  Further study of 6 sites on a single highly eroded stream showed high variability between sampling locations.  There was a significant effect for depth for β -galactosidase, protease, β -glucosidase, and acid phosphatase but not for phenol oxidase.  Higher activity was measured in surface soils than at 20 cm.  These results suggest the possibility of significant roles for the microbial community in nutrient cycling within hyporheic soils which may be related to degree of erosion.