HR: 16:15h
AN: NB24B-04    [Abstracts]
TI: The Effects of Urbanization on the Food Web of a Mid-order Stream in Rio de Janeiro, Brazil
AU: * Detweiler, A M
EM: amdetwei@uncg.edu
AF: Department of Biology, University of North Carolina - Greensboro, Greensboro, NC 27402 United States
AU: Hershey, A E
EM: aehershe@uncg.edu
AF: Department of Biology, University of North Carolina - Greensboro, Greensboro, NC 27402 United States
AU: Moulton, T P
EM: moulton@uerj.br
AF: Departamento de Ecologia, IBRAG, Universidade do Estado do Rio de Janeiro, Rua Sao Francisco Xavier, 524, Rio de Janeiro, RJ 20550-013 Brazil
AU: Brito, E F
EM: fuentesbrito@aol.com
AF: Departamento de Ecologia, IBRAG, Universidade do Estado do Rio de Janeiro, Rua Sao Francisco Xavier, 524, Rio de Janeiro, RJ 20550-013 Brazil
AB: Stream degradation caused by point source and non-point source pollution, loss of riparian vegetation, erosion and sedimentation can alter aquatic food webs. Due to the lack of proper sewage treatment, the main polluter in urban streams of Brazil is raw sewage. The purpose of this study is to determine if sewage-derived carbon and nitrogen are incorporated into the aquatic system and how this may affect the food web. We collected food web components at four sites along an urban stream, Rio Paineiras, and a reference stream, Rio Andorinha. Samples were analyzed for natural abundance of ¹³C and ¹⁵N. Raw sewage signatures were distinct and enriched compared to primary sources. Riparian vegetation and CPOM samples became significantly more enriched in ¹⁵N along the urban stream, compared to the reference stream. Periphyton ¹⁵N and ¹³C signatures were not significantly different between streams. Fish (Astyanax hastatus and Poecilids) showed some incorporation of sewage-derived ¹³C and ¹⁵N, in distinct trophic groups. Macroinvertebrate Hetaerina sp. reflected some incorporation of sewage-derived ¹⁵N. We also observed a reduction in functional feeding groups in the sewage-influenced reach of Rio Paineiras. Collectors, gatherers, and shredders were absent as stream degradation increased. Downstream communities were composed mostly of fish.
DE: 1803 Anthropogenic effects
DE: 4817 Food chains
DE: 4857 Pollution
DE: 4870 Stable isotopes
DE: 9360 South America
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly