BOG WETLAND HYDROLOGIC RESPONSE TO STORM RUNOFF: DOC CONCENTRATION AND CHEMICAL PROPERTIES

Wetlands have been known to be vital in controlling water quality and quantity within a watershed as they mediate water level fluctuations and filter pollutants (Mitsch and Gosselink, 2000). However, not all wetlands are alike and we do not fully understand their function in controlling stream water quality, especially under the dynamic conditions of storm runoff. Tannersville Bog, in Northeastern Pennsylvania, is a type of wetland largely detached from groundwater influence due to peat accumulation, which leaves surface water as the main water source. Dissolved organic carbon (DOC) exists in wetlands and may come from atmospheric deposition, canopy throughfall, decaying plants, or microbial photosynthesis on wetland or streambed surfaces (Aitkenhead-Peterson et al. 2003). DOC molecules serve valuable ecosystem functions in trophic interactions as a source of food for microbes (Meyer 1994). DOC also attenuates UV-B radiation to protect aquatic biota (Mulholland 2003). Understanding the DOC dynamics of Cranberry Creek as it flows through Tannersville Bog will contribute to a broader knowledge of wetland hydrologic response to rain storms. Automated measurements and sample collection at 5 sites along Cranberry Creek provide chemical, physical, optical, and flow data as the creek passes through Tannersville Bog. Analyses of specific conductance (indicator of groundwater-surfacewater mix), chromophoric dissolved organic carbon absorbance (controls UV attenuation), and the fluorescence ratio (parameter used to distinguish the DOC source) were performed to determine the quantity and quality and timing of DOC export during baseflow and storm conditions. CDOM absorbance increased downstream as the creek flowed through the bog during baseflow. During storm discharge the concentration of DOC increased with the rising phase of the hydrograph as others have observed for small streams, but time required for return to baseflow conditions was extended (especially during a large storm, 8.3 inches) with the consequence that DOC export from this wetland was elevated compared to other streams. Similar to other streams, the source of exported DOC shifted during a storm runoff from a mix of algal and terrestrial to primarily terrestrial DOC.