Sources of Energy in Subterranean Environments

Although subterranean habitats in general and caves in particular are often held to be extremely energy-poor (oligotrophic) environments, not all are. Compared to surface habitats, subterranean habitats are nutrient-poor, especially because there is no photo-autotrophic production and chemoautotrophy appears to be uncommon. On the other hand, these differences are not always pronounced. For example, the quantities of carbon fluxes in cave streams are in the range of those reported from surface streams. In some subterranean systems, chemoautotrophy is the main source of energy, but more typically subterranean communities depend on allochthonous sources of organic carbon. The major source of carbon in interstitial habitats is Dissolved Organic Matter (DOM) from surface waters. The major sources of carbon for cave communities are (1) water percolating from the surface, (2) sinking streams that enter caves, and (3) activities of animals moving in and out of caves.