Drying modulates cross-habitat subsidies and meta-ecosystem food webs in temporary saline inland waters

The connections between aquatic and adjacent terrestrial ecosystem in inland water through cross-habitat subsidies are increasingly recognized. However, we still have a limited understanding on how temporal variations of environmental factors (e.g., hydrological conditions) affect these flows. To address this gap, we investigated the effects drying has on cross-habitat subsidy flows and meta-ecosystem food webs by integrating both aquatic and terrestrial communities across the different hydrological phases (wet, contraction, and dry) in temporary saline lotic and lentic ecosystems. We analyzed the δ¹⁵N and δ¹³C signatures of aquatic and terrestrial basal subsidies, aquatic and terrestrial invertebrates, distinguishing between aquatic, riparian, shoreline and dry bed habitats. In the two temporary inland waters studied, drying of aquatic habitat and the subsequent expansion of the terrestrial habitat, significantly influenced cross-habitat subsidies and the meta-ecosystem food webs. In the wet and contraction phases, we found that the importance of aquatic subsidies in terrestrial food webs was constrained to terrestrial invertebrates near the aquatic habitat. Also, the contraction phase led to higher consumption of aquatic subsidies by aquatic and shoreline invertebrates, through a higher predation between aquatic invertebrates, and an enhanced accessibility of terrestrial invertebrates to aquatic subsidies. Whereas, riparian invertebrates showed prevalence for terrestrial subsidies throughout drying. Biofilm emerged as an important subsidy for both riparian and shoreline terrestrial invertebrates in the dry phase. In addition, the complexity of meta-ecosystem food web increased during drying, led by invertebrate diversity, omnivory and the type of temporary inland water. Our findings emphasize the significant impact drying has on cross-habitat subsidies and meta-ecosystem food webs, and the importance of integrating both aquatic and terrestrial communities in food web studies in temporary inland waters. This calls for further research to better understand the dynamics of temporary water ecosystems in the face of global change.