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crop organic matter significantly increased in the manipulation reach (159-866 g AFDM m -2 ),
while levels in the control reach remained low (9-75 g AFDM m -2 ; t-test: df = 8, t = -4.3, P =
0.003; Fig. 1a).
Macroinvertebrates
Forty-five different invertebrate taxa were identified from the core samples (Table 2).
Three taxa were identified as obligate cave species: Crangonyx, Stygobromus, and Caecidotea.
Six taxa could not be placed with confidence into either category: Cyclopoida, Harpacticoida,
Ostracoda, Oligochaeta, Chydoridae, and Nematoda. The remaining taxa were classified as
facultative cave species. Prior to the litter amendment, 23 and 22 taxa were documented from the
control and manipulation reaches, respectively. Richness increased in both reaches following the
litter amendment, with 31 taxa documented in the control reach and 37 taxa documented in the
manipulation reach. The increases in species richness following the litter amendment was driven
by increases in Diptera, especially of Chironomidae, and by Plecoptera taxa (Table 2).
Total macroinvertebrate biomass from core samples mirrored the patterns in standing
crop organic matter (Fig. 1b). Before the litter amendment, total macroinvertebrate biomass in
both study reaches was low but increased significantly (~5 times) in the manipulation reach
following the litter amendment (Wilcoxon signed rank test: n = 20, W = 44, P = 0.008).
Facultative species, rather than obligates, generally dominated total macroinvertebrate biomass
in both study reaches before and after the litter amendment. Facultative species accounted for 14-
77% of total macroinvertebrate biomass by date, while obligate cave species accounted for 0-
52% of total macroinvertebrate biomass. The lack of a significant biomass response to detritus
amendment by obligate cave taxa (t-test: df = 8, t = 1.1, P = 0.31) contrasted with the strong,
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