Disentangling responses of aquatic and terrestrial invertebrates to drying in saline streams and shallow lakes

In inland aquatic ecosystems, drying and salinity can co-occur as natural stressors, affecting aquatic invertebrate communities. Despite recent appreciation of the importance of temporary waterbodies for terrestrial invertebrates, knowledge about the effects of drying on dynamics of aquatic and terrestrial invertebrate communities is scarce, especially in saline ecosystems. This study analyzed structural and compositional responses of both communities to the coupled effects of drying and salinity in two streams and two shallow lakes in Spain, during three hydrological phases: wet, contraction, and dry. In the two studied saline streams, the contraction phase presented the highest aquatic and terrestrial abundance and richness, and the main compositional changes were mainly due, to an increase in aquatic lentic taxa (e.g., Coleoptera), and Araneae and Formicidae as terrestrial taxa. In shallow lakes, which presented highly variable salinity conditions, the highest abundance and diversity values were found at the wet phase for aquatic invertebrates and at the dry phase for terrestrial invertebrates. Compositional invertebrate community changes were due to a decrease in Rotifera and Anostraca (aquatic taxa) in the contraction phase for aquatic communities, and to an increase of Araneae, Coleoptera, and Formicidae (terrestrial taxa) at the dry phase for the terrestrial. Our study evidences the significant effect of drying on both aquatic and terrestrial invertebrates communities in natural inland saline waters and the need to integrate aquatic and terrestrial perspectives to study temporary inland waters.