Influence of environmental variables on the Oligochaeta (Annelida: Clitellata) community in a neotropical stream

Among the organisms of the benthic community, oligochaetes play a key role in the energy flow and recycling of organic matter in aquatic ecosystems, where their distribution is mainly influenced by local hydrological patterns. Thus, this study aimed to investigate the influence of environmental variables on the community of limnic oligochaetes in a neotropical lotic system. Galharada stream is located within the Campos do Jordão State Park (PECJ), in the state of São Paulo, Brazil, 1,600 m above sea level; 192 samples were collected from 4 sites selected according to their hierarchical order within the river basin (first to fourth order). To correlate the environmental variables to the oligochaete fauna, the Canonical Correspondence Analysis (CCA) was performed. We identified 16 species divided into 4 families (Enchytraeidae, Naididae, Pristinidae, and Tubificidae). The results of CCA revealed that the physical characteristics of stretches, such as stream depth and width, flow speed, and flow rate were the factors that most influenced on the structure of the aquatic Oligochaeta community in Campos do Jordão. The species Aulodrilus limnobius and Nais communis were considered along with the variables electrical conductivity and turbidity, indicating a possible association with environments enriched with organic matter. The occurrence of Enchytraeidae, Pristina rosea, Chaetogaster diastrophus, Pristina proboscidea, and Limnodrilus hoffmeisteri was seemingly uncorrelated to the environmental variables analyzed in this study. Our findings reinforce using the Oligochaeta community as bioindicators, by participating in the environmental assessment of continental aquatic ecosystems