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Regardless of strong selection pressures, cave systems can harbor a diverse array of vertebrate and invertebrate taxa that can be categorized into two groups, each with a distinct evolutionary history. One subset of the cave community is represented by obligate cave species, which share a similar set of characteristics (termed troglomorphic traits) that are presumed to be adaptations to the low-energy cave environment. These traits include K-selected life history characteristics (e.g. reduced growth rate and fecundity) and relatively low metabolic rates (Poulson & Lavoie, 2001; Hüppop, 2001, 2005). Another subset of the cave community consists of facultative cave species (e.g. surface species) that enter caves either actively (e.g., migratory or foraging movements) or passively (e.g., washed in during flood events). Some facultative species can survive and reproduce in both cave and surface environments, while others are “transients,” which subsequently either exit the cave or enter its food web as prey or carrion (Poulson & Lavoie, 2001; Hüppop, 2001, 2005). Under conditions of resource limitation, obligate cave species are assumed to have a competitive advantage due to their troglomorphic traits. However, when resource levels increase, facultative species may out-compete obligate cave species because of their ability to exploit available resources at higher rates (e.g. via higher growth rates and fecundities). Support for this hypothesis comes from reports of community shifts following incidental inputs of organic pollutants (Sinton 1984; Smith et al. 1986; Madsen et al. 1991; Notenboom et al. 1994; Simon and Buikema 1997; Sket 1999, 2005; Wood et al. 2002; Culver and Pipan 2009). Results from these studies, however, are confounded because organic pollution is typically a mixture of organic and inorganic material (i.e., organic matter, dissolved nutrients, microbes, and toxins), making it impossible to discern which component or combination of components causes changes in recipient communities. 41
More recent observational and experimental studies also support an energy-limitation hypothesis (see Datry et al. 2005; Cooney and Simon 2009; Schneider et al. 2011; Huntsman et al. 2011b). However, these studies only examined a portion of the community (e.g. only microbes or metazoan consumers). In this study we tested the energy-limitation hypothesis directly by amending a cave stream with detritus and then assessing the response of the entire cave stream food web, from microbes to top predators. We hypothesized that the detritus amendment would reduce energy limitation, resulting in variable population-level responses depending on different life history strategies (e.g. obligate cave versus facultative species). Because of the competitive differences within the cave community, we predicted that the carbon addition would increase biomass of both obligate and facultative cave species, but responses of facultative species would be of greater magnitude. Materials and Methods Study site This study was conducted in Bluff River Cave, Jackson Co., Alabama, U.S.A. The recharge area is mostly forested (mixed hardwoods) with very little urbanization; anthropogenic impacts on water quality therefore were assumed to be minimal. Bluff River Cave has ~1200 m of large passage (height 20 m, width 10 m), of which 1000 m is stream channel with a depth ranging from ~2 cm to 1.75 m during base-flow. Water depth can exceed 3 to 9 m during spates, however. Bluff River Cave contains a diverse assemblage of obligate cave and facultative species, including copepods, amphipods, isopods, larval insects (Chironomidae, Ephemeroptera and Plecoptera), the obligate cave crayfish Cambarus hamulatus, the facultative cave crayfish 42
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THE INFLUENCE OF ENERGY AVAILABILIT
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ABSTRACT Detritus from surface envi
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LIST OF ABBREVIATIONS AND SYMBOLS m
Page 7 and 8: NC IL ON U.K. VIAT VIE Fig. North C
Page 9 and 10: AIC K-S Akaike information criterio
Page 11 and 12: laboratory work and was an excellen
Page 13 and 14: LIST OF TABLES TABLE 2.1 TABLE 2.2
Page 15 and 16: LIST OF FIGURES FIGURE 2.1 (a) Box
Page 17 and 18: FIGURE 4.3 Growth models for Orcone
Page 19 and 20: chemolithoautotrophy-based systems;
Page 21 and 22: ecology, 51, 31-53. Gibert J. & Cul
Page 23 and 24: CHAPTER 2 EFFECTS OF ORGANIC MATTER
Page 25 and 26: community structure in cave “pits
Page 27 and 28: communities and how variation in co
Page 29 and 30: the different source locations was
Page 31 and 32: of natural-log transformed data (%
Page 33 and 34: peak in organic matter in Big Mouth
Page 35 and 36: Figs. 5a, b). The breakdown rate of
Page 37 and 38: per litter bag. Similarly, Huntsman
Page 39 and 40: ags was the greater retention of li
Page 41 and 42: Historically, limited resource inpu
Page 43 and 44: Culver, D.C. & Pipan, T. (2009) The
Page 45 and 46: Merritt, R.W., Cummins, K.W. & Berg
Page 47 and 48: Table 1. Mean (1 S.D.) macroinverte
Page 49 and 50: Table 2. Mean (±1 S.D.) daily temp
Page 51 and 52: Figure 1. (a) Box and whisker plot
Page 53 and 54: Figure 3. Non-metric multidimension
Page 55 and 56: Figure 5. Box and whisker plot of l
Page 57: streams, while the obligate-cave sp
Page 61 and 62: of netting (mesh size 2.5×1.5-cm)
Page 63 and 64: the two end-members. This conservat
Page 65 and 66: crop organic matter significantly i
Page 67 and 68: macroinvertebrate biomass to levels
Page 69 and 70: and surface streams (20-35,000 g m
Page 71 and 72: these factors, the stable isotope a
Page 73 and 74: surface streams. Thus, it is likely
Page 75 and 76: subsides to ecosystem dynamics have
Page 77 and 78: populations. Journal of Applied Eco
Page 79 and 80: Poulson T.L. & Lavoie K.H. (2001) T
Page 81 and 82: Wood P., Gunn J. & Perkins J. (2002
Page 83 and 84: Table 2. Mean (±1 standard deviati
Page 85 and 86: Table 2. Continued Chironomini Para
Page 87 and 88: Figure 1. Mean (bars are standard e
Page 89 and 90: Figure 3. Non-metric multidimension
Page 91 and 92: CHAPTER 4 REXAMINING EXTREME LONGEI
Page 93 and 94: individuals, he predicted that it w
Page 95 and 96: A phylogeographic study by Buhay &
Page 97 and 98: differences in size structure among
Page 99 and 100: and females in Tony Sinks Cave were
Page 101 and 102: Estimates of life span for O. austr
Page 103 and 104: available size-classes were well re
Page 105 and 106: References Anonymous (1999) Cave Sc
Page 107 and 108: Huryn A.D. & Wallace J.B. (1987) Pr
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Whitmore N. & Huryn A.D. (1999) Lif
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Table 2. Estimated life span (years
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Figure 1. Annual growth increment (
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Figure 3. Growth models for Orconec
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CHAPTER 5 CONSUMER-RESOURCE DYNAMIC
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following incidental inputs of orga
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Temperature data were not available
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minimum (Venarsky et al., 2012b). A
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100% organic matter (i.e., maximum
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Macroinvertebrate biomass varied si
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Discussion The energy-limitation hy
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crayfish captured in most months we
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systems is likely high, especially
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function of microbial films in grou
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Crustacean Biology, 4, 35-54. Momot
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Whitmore N. & Huryn A. (1999) Life
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Table 2. Assimilation efficiencies
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Table 3. Continued Tanypodinae 0.03
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Table 5. Estimates of mean wood and
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Figure 1. (A) Box and whisker plot
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CHAPTER 6 OVERALL CONCLUSIONS Due t
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characteristics (e.g., higher growt
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characteristics, highly efficient p
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