Summer DOC concentrations were lowest at the 3 streams with the most vegetated catchments (mean of 1.3 mg/l), and highest in the urban streams (3.3 mg/l), with suburban streams having intermediate values (2.2 mg/l). Additionally, a mean of 8.5 mg/l was seen in a residential storm drain groundwater flow. Mean areal summer instantaneous DOC fluxes at forested, suburban and urban streams were 0.18, 0.41 and 0.85 mg/s/ha, respectively (5.5, 12.6, 26.1 kg/ha/yr).
Mean dry weather FPOM concentrations ranged from 0.38 mg/l (restored suburban) to 2.77 mg/l (forested). OM % (of TSS) ranged from 13% (restored suburban) to 31 % (forested), to 62% at a sewage impacted underground stream. Flows influenced by recent storms had higher FPOM concentrations, by factors of 18 (forested), 23 (suburban) and 5 (urban). At a suburban stream storm monitoring station, TSS and FPOM concentrations responded strongly to flow rate (power function slopes of 0.67 and 0.42 respectively). The % organic matter (of TSS), however, decreased with flow rate (slope = -0.25).
These results suggest that urban catchments, with their altered drainage pathways and strong terrestrial-aquatic linkages, can transport appreciable quantities of dissolved and particulate organic matter. This has implications for aquatic food webs and productivity, and for pollutant fates. It also suggests that restoration might play a role in facilitating the retention of this
