Community structure of macroinvertebrates in freshwater rock pools of the Brazilian semiarid region

Luciana L. Santos, Frederico Alekhine Chaves Garcia, Marcos Adelino Almeida Filho, Milena Gonçalves-Silva , Fernando Eggers Reichert, José Roberto Feitosa, Carla Ferreira Rezende

Freshwater rock pools (FRPs) are temporary aquatic environments that provide refuge for biodiversity in regions with low precipitation. The macroinvertebrate communities of FRPs in the Brazilian semi-arid region constitute an important link between aquatic and terrestrial ecosystems, given their dependency on both to complete their life cycles. The knowledge about FRPs and their resident biota remains scarce, compromising effective conservation actions. In this study, we investigated the influence of dispersal mode and local environmental conditions on the structure of macroinvertebrate communities. We sampled 16 FRPs on a unique, continuous inselberg in the Brazilian semi-arid region during the wet and dry seasons of 2013. In each rock pool, we collected macroinvertebrates and measured local environmental variables related to water characteristics and pool morphology. We observe that seasonal variation influences the predominant dispersal mode of macroinvertebrate communities, while local environmental conditions shape their composition. Active dispersers were predominant in both wet and dry seasons. However, during the dry season, the abundance of passive dispersers increased sevenfold relative to that of active dispersers. Community composition was significantly influenced by dissolved oxygen, pH, water temperature, and electrical conductivity. These findings highlight the importance of FRPs as habitat refuges for aquatic biota from semiarid regions.