Drought and aquatic community resilience: the role of eggs and seeds in sediments of temporary wetlands

Abstract

Summary 1. A long‐lived bank of propagules consisting of eggs, seeds and spores is one mechanism that allows aquatic communities to survive drought. A drying (drought) event is, for aquatic organisms in a temporary wetland, a phase from which communities must recover. Such a dry phase is often considered a disturbance but should not be considered adverse or catastrophic for the organisms that have evolved to live in temporarily wet habitats. 2. This paper explores the parallels between the egg bank of zooplankton and the seed bank of aquatic plants as means of survival in temporary wetlands. The resilience of communities in temporary wetland ecosystems is assessed by examining dormancy, hatching, germination, establishment and reproduction of animals and plants from the egg and seed banks of wetlands with a range of wetting and drying regimes. 3. Both the zooplankton and aquatic plants of the temporary wetlands studied rely on their egg and seed banks as a means for surviving drying. These communities recover after the disturbance of drying by means of specific patterns of dormancy, dormancy breakage, hatching, germination, establishment and reproduction. Spatial and temporal patterns of species richness allow resilience through dormancy, as not all species are present at all sites and not all species hatch and germinate at the same time. Multiple generations in the egg and seed bank and complexity of environmental cues for dormancy breakage also contribute to the ecosystem's ability to recover after a drying event. A persistent egg and seed bank allows species‐rich communities to hatch, germinate and develop rapidly once dormancy is broken. Rapid establishment of species‐rich communities that reproduce rapidly and leave many propagules in the egg and seed bank also facilitates community recovery on flooding of a temporary wetland after a drying event. 4. To maintain the diversity of temporary wetland communities through droughts and floods we need to manage the dry and wet phases of wetlands. To conserve a wide range of wetland types, we need to maintain a variety of hydrological patterns across the landscape.

Fringing trees may provide a refuge from prolonged drying for urban wetland invertebrates

“…Flexibility in hatching or emergence timing within species has been observed in other studies of both crustaceans and insects (e.g. Brock et al 2003;Wickson et al 2012).…”

The impacts of drought on freshwater ecosystems: an Australian perspective

“…many fish and waterbirds; Unmack, 2001;Kingsford & Norman, 2002;Graham & Harris, 2005;Poiani, 2007). Australian aquatic fauna and flora are characterised by the high prevalence of both resistance and resilience traits, reflecting the evolutionary significance of drought as a selective pressure on aquatic biota and ecosystems (Boulton, 2003;Brock et al, 2003).…”

Density‐dependent life history differences in a stream mayfly (Deleatidium) inhabiting permanent and intermittent stream reaches

“…Falling water often acts as a seasonal cue, e.g., most predictable temporary systems fall dry in late summer/early autumn, for aquatic organisms to either complete development and leave the system (Delucchi & Peckarsky 1989;Donath & Robinson 2001) or enter into a stage of diapause to wait for resumption of flowing water (Williams 1996). For instance, many insects have drought resistant eggs that allow them to survive seasonal dry periods (Brock et al 2003).…”