TITLE PAGE - acumen - The University of Alabama
TITLE PAGE - acumen - The University of Alabama TITLE PAGE - acumen - The University of Alabama
predicted the energetic demands of O. australis would be roughly equivalent to the resources available for consumption in each cave. This prediction was tested using the trophic basis of production approach (Benke & Wallace, 1980) and different energetic scenarios that included potential resource supply rates within the cave streams, combined with potential crayfish diets (e.g. detritivory vs. strict predation). Materials and Methods Study sites Three caves containing streams in northeastern Alabama (Jackson County, U.S.A.) were chosen for study: Hering, Limrock, and Tony Sinks. These caves contained large populations of O. australis and had similar macrofaunal assemblages, which included the facultative cave crayfish Cambarus tenebrosus and the obligate cave salamander Gyrinophilus palleucus. The southern cavefish (Typhlichthys subterraneus) and the mottled sculpin (Cottus bairdi) also occurred in Limrock and Hering caves. During this 5+-year study, O. australis was by far the most abundant of these species and generally represented >95% of the total number of individuals encountered for all species on each sampling date. This suggests O. australis was also the largest consumer of resources within the cave streams. A study reach ranging from 327 to 1202 m in length (1298 to 5323 m 2 ), containing a series of riffle and pool habitats with sand, gravel, and bedrock substrates, was established in each cave. Stream area was estimated in September 2010 by measuring stream width at 10-m intervals. Water temperature Water temperature was recorded in each stream every 30 minutes using a Solinst Barologger model 3001 (Solinst, Georgetown, Ontario, Canada) from June 2007 to July 2011. 103
Temperature data were not available for Tony Sinks from March 2009 to January 2010 due to instrument loss. Standing crop organic matter and macroinvertebrates On each of four dates (March, July and November 2009 and February 2010) fifteen random samples were collected from each cave using a 22.5-cm diameter corer to quantify benthic organic matter and macroinvertebrate biomass. The corer was inserted into the stream bottom, large organic matter was removed, and the substrate was disturbed to a maximum depth of 4 cm. Remaining suspended organic matter was removed from the corer via ten sweeps of the water column with a 250-µm mesh net. Samples were returned to the laboratory on ice and processed within 48 hours. Once returned to the laboratory, samples were processed through a 250-µm sieve and all macroinvertebrates were removed and preserved in 5% formalin. The remaining organic matter was dried at 60 o C for ~2 weeks, weighed, combusted at 500 o C for 6 h, and then weighed again to estimate ash-free dry mass (AFDM). Macroinvertebrates were identified to the following levels: family/tribe for insects, class or order for microcrustaceans, class for annelids, and phylum for nematodes. Dry mass was estimated using published length-mass relationships (Calow, 1975; Culver et al., 1985; Leeper & Taylor, 1998; Benke et al., 1999; Lemke & Benke, 2004; Doroszuk et al., 2007). Macroinvertebrate dry mass was converted to AFDM assuming AFDM is 93% of dry mass (Benke & Wallace, 1980). Using Data Desk version 6.1 (Data Description Inc., 1996), a two-way analysis of variance (factors – cave and sampling date) was conducted to examine differences in standing crop organic matter and macroinvertebrate biomass among caves. 104
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predicted the energetic demands <strong>of</strong> O. australis would be roughly equivalent to the resources<br />
available for consumption in each cave. This prediction was tested using the trophic basis <strong>of</strong><br />
production approach (Benke & Wallace, 1980) and different energetic scenarios that included<br />
potential resource supply rates within the cave streams, combined with potential crayfish diets<br />
(e.g. detritivory vs. strict predation).<br />
Materials and Methods<br />
Study sites<br />
Three caves containing streams in northeastern <strong>Alabama</strong> (Jackson County, U.S.A.) were<br />
chosen for study: Hering, Limrock, and Tony Sinks. <strong>The</strong>se caves contained large populations <strong>of</strong><br />
O. australis and had similar macr<strong>of</strong>aunal assemblages, which included the facultative cave<br />
crayfish Cambarus tenebrosus and the obligate cave salamander Gyrinophilus palleucus. <strong>The</strong><br />
southern cavefish (Typhlichthys subterraneus) and the mottled sculpin (Cottus bairdi) also<br />
occurred in Limrock and Hering caves. During this 5+-year study, O. australis was by far the<br />
most abundant <strong>of</strong> these species and generally represented >95% <strong>of</strong> the total number <strong>of</strong><br />
individuals encountered for all species on each sampling date. This suggests O. australis was<br />
also the largest consumer <strong>of</strong> resources within the cave streams. A study reach ranging from 327<br />
to 1202 m in length (1298 to 5323 m 2 ), containing a series <strong>of</strong> riffle and pool habitats with sand,<br />
gravel, and bedrock substrates, was established in each cave. Stream area was estimated in<br />
September 2010 by measuring stream width at 10-m intervals.<br />
Water temperature<br />
Water temperature was recorded in each stream every 30 minutes using a Solinst<br />
Barologger model 3001 (Solinst, Georgetown, Ontario, Canada) from June 2007 to July 2011.<br />
103
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