Long-term droughts change the hatching patterns of zooplankton resting eggs from permanent and temporary lakes

Abstract

Resting eggs are commonly produced by zooplankton inhabiting permanent and temporary lakes. Although resting eggs are acknowledged to survive varying harsh conditions, the effects of desiccation on the viability and hatching patterns of resting eggs are not fully understood and might be context-dependent. This study simulated one long-term (1 year) dry-out episode in wet sediments originating from permanent and temporary lakes and compared hatching patterns through ex situ experiments. The abundance and species richness of hatchlings decreased in dry sediments compared to wet sediments. Hatchling composition differed between wet and dry sediments of each lake category, whereas community variability did not differ between wet and dry sediments of temporary lakes. Overall, there was no difference in the ability of rotifers and crustaceans to cope with desiccation, since all species decreased hatchling numbers after desiccation. Artemia was the only taxon that benefited from drying sediments. Long-term desiccation may affect the contribution of resting egg banks to future active populations in the water column, even in temporary habitats which presumably select for drought-resistant resting eggs. The ecological roles played by resting egg banks may be weakening because droughts are becoming more common worldwide, even in former permanent aquatic habitats.