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Presented at the NABS Annual meeting, Pittsburgh, Pennsylvania, 2002
in Land/Water Interfaces
EFFECTS OF RIPARIAN DEGRADATION ON CRAYFISH AND BENTHIC INSECTIVORE TERRESTRIAL CARBON DEPENDENCE IN HEADWATER TROUT STREAMS.
L.E. England and A.D. Rosemond. Institute of Ecology, University of Georgia, Athens, GA, 30605, USA
Riparian forests impact a multitude of physical, chemical, and biological dimensions of aquatic ecosystems. Among these impacts is the important role that terrestrial carbon inputs from riparian forests play in supporting and structuring aquatic food webs. At present, human encroachment has converted most riparian forests to narrow, discontinuous corridors of vegetation along streams embedded within watershed matrices of anthropogenic land uses. This study assessed the impact of such riparian degradation on the terrestrial carbon dependence of crayfish and benthic insectivorous fish in 7 headwater trout streams in the Upper Chattahoochee River basin, Georgia, USA. GIS techniques were used to classify 1999 color-infrared aerial photographs of study watersheds, and several assessments of riparian degradation were made. Basal food resources (algae, CPOM, FBOM, and seston), crayfish, and benthic insectivorous fish were collected and analyzed for natural abundance of stable carbon isotopes. Basal resource δ13C signatures had no relationship with riparian degradation. However, crayfish as well as three fish species δ13C signatures showed significant enrichment with riparian degradation, such that biota δ13C diverged from CPOM δ13C with increasing riparian degradation. Thus, the dependence of aquatic food webs on terrestrial carbon decreased with increasing riparian degradation in these headwater streams.
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