TITLE PAGE - acumen - The University of Alabama
TITLE PAGE - acumen - The University of Alabama
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CHAPTER 5<br />
CONSUMER-RESOURCE DYNAMICS IN A CAVE STREAM ECOSYSTEM<br />
Abstract<br />
In cave ecosystems, energy limitation is hypothesized to be the primary factor<br />
influencing evolutionary and ecological processes. In this study, the energy-limitation hypothesis<br />
was tested by comparing the energetic demands <strong>of</strong> the obligate cave crayfish Orconectes<br />
australis to resource supply rates in three separate cave systems with varying quantities <strong>of</strong> food<br />
resources (i.e. organic matter and macroinvertebrate prey). Crayfish population size, biomass,<br />
and secondary production were estimated using a 5+-year mark-recapture data set from each<br />
cave. Crayfish demand was compared to resource supply rates using the trophic basis <strong>of</strong><br />
production approach. Several different energetic scenarios were modeled that included different<br />
crayfish diets and resource supply rates. Detrital storage and macroinvertebrate biomass covaried<br />
among caves, ranging from 22 to 132 g AFDM m -2 and 27 to 320 mg AFDM m -2 , respectively.<br />
Crayfish population sizes (1311 to 5044 individuals), biomass (80 to 862 mg AFDM m -2 ) and<br />
secondary production (21 to 335 mg AFDM m -2 yr -1 ) mirrored the patterns in resource<br />
availability among caves, providing further support for the energy-limitation hypothesis.<br />
Energetic models constructed using a crayfish diet based on plant detritus only indicated that<br />
crayfish demand would be lower than supply rates. However, models based on a<br />
macroinvertebrate prey diet indicated that the crayfish populations would consume nearly all<br />
macroinvertebrate prey production within each cave. Collectively, the results from this study<br />
provide robust support for the energy-limitation hypothesis, but also show that cave ecosystems<br />
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