Edmonds, J. W. Arizona State University, jedmonds@asu.edu
Grimm, N. B. Arizona State University, nbgrimm@asu.edu
Fisher, S. G. Arizona State University, S.Fisher@asu.edu

 
SPATIAL AND TEMPORAL PATTERNS IN DISSOLVED ORGANIC MATTER CHEMICAL COMPLEXITY ALONG A NATIVE DESERT TO URBAN STREAM GRADIENT: CAUSES AND CONSEQUENCES
 
Ecological research suggests that organic matter chemical complexity and heterotrophic bacterial activity are egatively correlated. Because of our interest in microbial production and cycling of nutrients in Sonoran Desert riparian-stream ecosystems, we asked: What influences temporal and spatial patterns in dissolved organic matter (DOM) chemical complexity along a gradient from native desert to urban ecosystem? DOM chemical complexity was measured using specific ultraviolet absorbance (SUVA) and spectrofluorometric index (FI) of waters from Sycamore Creek, AZ (desert) and from streams and canals of metropolitan Phoenix, AZ (urban). DOM chemical complexity was high in riparian waters and lower in active channel subsurface waters. Temporal patterns suggest that floods deliver highly aromatic, chemically complex DOM, which probably originates from wetted dry fall and runoff over DOM-rich terrestrial soils, to Sycamore Creek. Inputs to and outputs from the Phoenix metropolitan area showed temporal and spatial variability in SUVA and FI values. Likely causal mechanisms for this heterogeneity include discharge, land use, and influence of engineered structures. Sediments were incubated with different sources of DOM to evaluate the chemical complexity-bacterial activity relationship. SUVA and FI responded to chemical changes in DOM, but small chemical differences did not result in differences in aerobic respiration rates.
 
Day: Tuesday, Feb. 2
Time: 04:30 - 04:45pm
Location: Eldorado Hotel
 
Code: SS34TU0430E