Trophic dynamics in a neotropical limestone cave

Abstract

The temporal budgets of the input, retainment and use by invertebrates of detritus and root tufts were evaluated in a short tropical limestone cave (337 m long). Detritus penetrate only through the stream in lower quantities in the dry season, contrary to what happens in the rainy season. However, water transport energies in the rainy season prevent detritus retainment. Roots tufts that emerge from the bottom of the stream provide shelter and food for several species. The abundance (log10) (R2 = 0.63; P < 0.02) and richness (log10) (R2 = 0.63; P < 0.01) related positively with the root tuft biomass (log10). In the terrestrial environment (ground), guano is the main secondary resource available for the invertebrates; the constant production of this resource has shown to influence the structure and distribution of invertebrates. Unfavorable temperature conditions and, especially low soil moisture, promote low plant detritus consumption rates. Historically, different authors assumed that organic resources imported by water are more available in caves in rainy seasons. It is clear that the importation of organic detritus in the rainy season is higher than in the dry season, but as shown in this work, the stochastic pulse flows continually disturb and remove the previously accumulated resource. So, the food that is truly used by the cave communities is that transported at the end of the rainy season (and during all the dry season) that becomes available for the cave fauna. The cave functionality depends, so, directly of the epigean food resources.