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If some cave and surface stream ecosystems share similar community structures and environmental characteristics, do they also have a similar response to changes in allochthonous inputs of detritus? A study by Wallace et al. (1999) reduced allochthonous inputs of detritus (e.g. leaf-litter and woody debris) to a forested headwater stream by 95% over a 4-year period. The exclusion experiment reduced organic biomass within the stream by ~77%, which subsequently reduced macroinvertebrate biomass by ~78%. Comparing the results of Wallace et al. (1999) with those from this and two previous cave stream studies shows that Wallace et al. (1999) essentially transformed a high-energy surface stream into a high-energy cave stream, while the experiment conducted in this study converted a low-energy cave stream into a low-energy forested headwater surface stream (Fig. 4). Thus, some cave and surface streams are fundamentally similar and appear to be linked to one another along a detrital subsidy spectrum that includes both high (e.g. surface) and low (e.g. cave) rates of detrital inputs. While cave and forested headwater streams appear to be linked along a detrital subsidy spectrum, they are substantially separated along a time continuum. The results of this study and those of Wallace et al. (1999) illustrate the importance of detrital inputs on short-term ecological time scales, while unmanipulated cave ecosystems exemplify how detrital exclusion on evolutionary time scales influences the evolution of specialized life histories and physiologies that prevent obligate cave species from responding to short-term increases of energy resources. Conclusions Detrital inputs are the primary source of energy fueling biological productivity within many cave ecosystems and are also important in structuring their communities. However, little attention has been given to quantifying energy dynamics in cave ecosystems. This is in stark contrast to aquatic surface ecosystems, in which the importance of detrital pathways and resource 57
subsides to ecosystem dynamics have been appreciated for many years. Numerous studies within aquatic surface ecosystems have explored how the quantity, quality, and type of detrital inputs influence ecosystem processes and the structure of microbial-, meio-, and macro-faunal communities (see Moore et al. 2004). This study begins to close this knowledge gap by providing the first rigorous experimental test of the energy-limitation hypothesis in cave ecosystems. Similar to several recent studies (Datry et al., 2005; Cooney & Simon, 2009; Huntsman et al., 2011b; Chapter 5), the results of this study provide robust support for the energy-limitation hypothesis in cave ecosystems, finding that detrital inputs are important in structuring aquatic cave communities. However, the distinct evolutionary histories (e.g. facultative vs. obligate) dictated the species-level responses to short-term increases in energy availability. Additionally, this study illustrates how cave and surface stream ecosystems have much more in common than previously thought due to their similarities in community structure and responses to fluctuations in energy inputs. Lastly, several recent studies have illustrated that energy inputs can vary greatly among caves, indicating that energy limitation varies among cave ecosystems (Simon & Benfield, 2001, 2002; Huntsman et al., 2011 a, b; Venarsky et al., 2012; see Chapter 5). Thus, additional experimental and natural-gradient studies conducted over longer time-periods and including wider ranges of energy availabilities are required to develop a more complete understanding of cave ecosystem energy dynamics. References APHA (1998) Standard methods for the examination of water and wastewater. Washington, DC: American Public Health Association. Bärlocher F. & Kendrick B. (1981) Role of aquatic hyphomycetes in the trophic structure of streams. In: The Fungal Community: Its Organization and Role in the Ecosystem. (Eds D.T. Wicklow & G.C. Carroll), pp. 743-760. Marcel Dekker, New York. Bender M.M. (1968) Mass spectrometric studies of carbon-13 variations in corn and other 58
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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
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NC IL ON U.K. VIAT VIE Fig. North C
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AIC K-S Akaike information criterio
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laboratory work and was an excellen
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LIST OF TABLES TABLE 2.1 TABLE 2.2
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LIST OF FIGURES FIGURE 2.1 (a) Box
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FIGURE 4.3 Growth models for Orcone
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chemolithoautotrophy-based systems;
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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 and 58: streams, while the obligate-cave sp
Page 59 and 60: More recent observational and exper
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: surface streams. Thus, it is likely
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
Page 109 and 110: Whitmore N. & Huryn A.D. (1999) Lif
Page 111 and 112: Table 2. Estimated life span (years
Page 113 and 114: Figure 1. Annual growth increment (
Page 115 and 116: Figure 3. Growth models for Orconec
Page 117 and 118: CHAPTER 5 CONSUMER-RESOURCE DYNAMIC
Page 119 and 120: following incidental inputs of orga
Page 121 and 122: Temperature data were not available
Page 123 and 124: 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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