TITLE PAGE - acumen - The University of Alabama
TITLE PAGE - acumen - The University of Alabama
TITLE PAGE - acumen - The University of Alabama
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Energy budgets<br />
Several different energetic scenarios were modeled in this study using potential crayfish<br />
diets and resource supply rates so that the energy-limitation hypothesis could be explored from<br />
an energy-dynamics perspective. Collectively, the energy budgets constructed for O. australis do<br />
not show that crayfish demand is higher than resource supply rates, which indicates that resource<br />
deficits do not exist and that these populations do not require more resources than are present<br />
within the cave stream channels.<br />
In this study, the energetic demands <strong>of</strong> crayfish populations were bracketed between<br />
strict detritivory and strict predation. While leaf and wood supply rates were large enough in all<br />
caves to fulfill crayfish demand, it is unlikely that O. australis feeds strictly on detritus because:<br />
i) the majority <strong>of</strong> growth in juvenile surface crayfish taxa has been attributed to the consumption<br />
<strong>of</strong> animal material (Whitledge & Rabeni 1997), ii) both surface and cave crayfish are known to<br />
be omnivorous (Weingartner, 1977; Nystrӧm, 2002; Parkyn et al., 2001), and iii) O. australis<br />
maintained in the laboratory does not consume conditioned leaf litter (M.P. Venarsky, personal<br />
observation). Thus, these populations <strong>of</strong> O. australis were most likely supported by<br />
macroinvertebrate production, rather than organic matter.<br />
<strong>The</strong> energetic models based on a macroinvertebrate diet suggest that the Hering and Tony<br />
Sinks populations <strong>of</strong> O. australis consumed all <strong>of</strong> the macroinvertebrate production, while a very<br />
small surplus <strong>of</strong> macroinvertebrate production was present in Limrock. <strong>The</strong>se results suggest O.<br />
australis is likely limited by macroinvertebrate production, which is not a feature unique to cave<br />
ecosystems. <strong>The</strong> near complete consumption <strong>of</strong> prey production by predators has been observed<br />
in several surface streams (see Huryn & Wallace, 2000). Because <strong>of</strong> the limited potential for<br />
prey surpluses, competition for resources among O. australis and other predators in these cave<br />
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