Site-Specific Processes at Sugar Creek
Environmental processes were examined in detail at Sugar Creek using three sites selected to maximize stream bed variability. Porewater samples (<30 mL) were collected by pumping from six depths beneath the sediment surface. To determine the presence of denitrifying bacteria, the nitrite-reductase gene (nirS) DNA was amplified by polymerase chain reaction (PCR) using the forward primer niR1 and the reverse primer niR2 from DNA extracted from subcores collected at each depth (red arrow indicates nirS product in gel photos). Penetration of surface water into the subsurface was assessed from tracer Br concentrations at site 4.6, and also from variations in pore-water chloride concentrations at site 3.2. Tracer results indicate varying depths of penetration of surface water carrying nitrate into the stream-bottom sediments.
| 3
sites compared |
Observations |
Implications |
|
Good Surface Water Good Periphyton Coverage Organic Rich Surface |
Deep Denitrification
activity Denitrification rate high |
 |
Limited surface water penetration Minor periphyton coverage Organic-rich surface |
No deep
denitrification activity Denitrification rate moderate |
 |
Good surface water
penetration No periphyton coverage No organic-rich surface |
Deep Denitrification
activity Denitrification rate low |
