Dormant structures of aquatic microfauna: ecological aspects and perspectives on different climate temperature scenarios.

Abstract

Dormancy is a biological process that allows communities to survive in adverse environmental conditions. The production of dormant structures is one of the main strategies performed by aquatic microfauna (ciliates, rotifers, cladocerans, copepods and ostracods). This study aimed to evaluate the dormant structures of aquatic microfauna, addressing different ecological aspects such as hatching time, dispersal, fungal influence and viability of the structures at different temperatures. The hatching experiments were performed with sediment and aquatic macrophytes of lakes from the upper Paraná River floodplain, Brazil. The results evidenced that ostracod resting eggs have similar hatching times among taxonomically close species and that the functional traits of the species (e.g. body size and presence of spines) influence the hatching time. In addition, dried roots of the free floating macrophyte (Eichhornia crassipes) shelter and disperse ostracod resting eggs. While, for all dormant aquatic microfauna a positive effect was observed between the presence of fungi in the sediment and species richness of the dormant communities, which did not negatively influence the viability of the dormant structures. The results also showed that the increase in temperature reduced significantly the species richness of the dormant microfauna and led to homogenisation of the egg bank. Based on the results, we highlight the importance of dormant structures in the recolonisation of environments and the high potential for dispersal by biotic vectors (plants), however this is also a warning for the invasion process. In addition, climate change responsible for temperature increase is a threat to the dormant structures of aquatic microfauna, thus it necessary to create mitigation measures for the conservation of the egg bank.