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Presented at the NABS Annual meeting, Pittsburgh, Pennsylvania, 2002
in Urban Ecology I
RELATIONSHIP BETWEEN ECOSYSTEM METABOLISM AND BASEFLOW DISCHARGE IN AN URBAN REGULATED RIVER.
C.A. Gibson and J.L. Meyer. Institute of Ecology, University of Georgia, Athens, GA 30602
How have human alterations to the landscape influenced the ability of stream ecosystems to process nutrient and organic matter inputs? We examined this question by determining the variation in ecosystem metabolism under baseflow conditions in a nutrient rich, turbid, regulated, urban river: Chattahoochee River, Atlanta, GA USA. We hypothesized that gross primary production would decrease with increasing discharge and respiration would increase with increasing discharge, but the system would remain heterotrophic. Metabolism was measured on 18 days in summer 2001 and 6 days in summer 2000 using the open-channel oxygen change method. Discharge for these dates ranged from 28 m3s–1 to 64 m3s–1 which was much lower than the mean summer discharge of 93 m3s–1. GPP was 0.64 gO2m-2d-1 at 28 m3s–1, 1.24 gO2m-2d-1 at 31 m3s–1, and 2.08 gO2m-2d-1 at 43 m3s–1. Respiration was 3.04 gO2m-2d-1 at 28 m3s–1, 5.28 gO2m-2d-1 at 31 m3s–1, and 7.22 gO2m-2d-1 at 43 m3s–1. Preliminary analysis suggests that our hypothesis was not supported because GPP appears to increase with discharge and there is not a clear relationship between respiration and discharge. However, the system was heterotrophic for all sampling dates.
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