ABSTRACT Caves are commonly stable environments and hold a unique biodiversity.The importance of water as a vehicle of food resource input and as the habitat of many aquatic organisms is well known. This importance is even greater in subterranean ecosystems. However, there is a lack of studies concerning the subterranean aquatic invertebrate fauna in Brazil. The objective of this study was to characterize the aquatic environment and fauna of a limestone cave located in the state of Minas Gerais (Southeastern Brazil). The relations between the benthic invertebrate fauna and the aquatic environmental characteristics were also analyzed. All the data was obtained in a single sampling event in the rainy season. The stream was divided in 8 sampling stations in a limestone cave “Gruta do Retiro” (Brazil). The diversity (Shannon Index) and similarity (Bray-Curtis) among the stations were analyzed, as well as the aquatic fauna and its relation with environmental variables. The physical-chemical characteristics analyzed were: temperature, dissolved oxygen, electric conductivity, pH, velocity of water flow and percentage of organic matter present in the sediment. To evaluate the influence of the abiotic data over the richness of invertebrates, a non-parametric test (Spearman) was performed. A total of 4,490 organisms distributed among the Arthropoda, Annelida, Mollusca, Nematoda and Platyhelminthes taxa were identified. The Arthropoda was the most representative taxa with species from the Insecta, Arachnida and Crustacea groups. Dissolved oxygen, temperature and electric conductivity presented significant relation with the distribution of some aquatic organisms. Keywords: cave, benthic fauna, aquatic invertebrates, Pains, Brazil. 1. INTRODUCTION Caves may be formed in an array of lithologies. The distinguish characteristics of each rock type may lead to different environmental features. Most of the known caves are formed in carbonatic rocks due to their high solubility and exposure to water flows (Ginés and Ginés 1992; Gillieson 1996). The chemical nature of the rock where a cave is formed promotes different environmental characteristics on the aquatic system. The alkaline nature of carbonate rocks in karst areas may cause hardness of underground freshwater. The hardness observed in karstic watersheds is usually caused by the high levels of dissolved CaCO3 in these areas through dissolution of the carbonate rocks (Zhang et al 2000). The precipitation of calcite may occur through natural processes of water softening, such as enhancement of velocity of water flow and outgassing of CO2 at the surface.
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