PARENT SESSION
Oral Session #46: Disturbance Ecology.
Presiding: M. Slocum
Tuesday, August 6. 1:00 PM to 4:45 PM. Grand Ballroom East, Radisson.
Habitat-based, hierarchical analysis of disturbance in a tropical stream.
HAYWARD, APRIL*,1, BIGGERS, ANDY1, WALTHO, NIGEL1, KOLASA, JUREK2, 1 Lumbers Building, York University, Toronto, ON, Canada2 Department of Biology, McMaster University, Hamilton, ON, Canada
ABSTRACT- Although a great deal of research toward understanding the nature of the effects of dams on stream ecosystems has been carried out, much of this research has relied on the use of community-level diversity indices to assess differences between communities above and below dams. We attempt to increase the analytic resolution of such studies. By partially decomposing benthic assemblages into discrete groupings, based on species habitat specialization (ecological range), we attempt a more robust and meaningful analysis of community response. Surber and Ekman samples were taken from a variety of habitats above and below a hydro-electric dam on a stream in Jamaica. Relative abundance and ecological range were used to group species into habitat specialists, intermediates, and generalists. In the absence of disturbance, hierarchy theory suggests that species-level variation between sites in specialist groups should be greater than that in intermediate groups; generalist groups should vary least. However, results of this study indicate that the below dam variation in relative species abundances is similar among groups (as defined at the reference site, above the dam). This implies a complete re-organisation of community structure and indicates intense benthic community disturbance. Further, results indicate that specialist species have been displaced by generalists and that the absolute abundance of all species has decreased below the dam.
KEY WORDS: Dam effects, disturbance, benthic invertebrates, hierarchy theory