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

Authors

  • M. A. Brock,

    1. Centre for Natural Resources, NSW Department of Land & Water Conservation, NSW, Australia
    2. Co-operative Research Centre for Freshwater Ecology (CRCFE), Albury, NSW, Australia
    3. Botany, University of New England, Armidale, NSW, Australia
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  • Daryl L. Nielsen,

    1. Co-operative Research Centre for Freshwater Ecology (CRCFE), Albury, NSW, Australia
    2. Murray-Darling Freshwater Research Centre (MDFRC), Albury, NSW, Australia
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  • Russell J. Shiel,

    1. Co-operative Research Centre for Freshwater Ecology (CRCFE), Albury, NSW, Australia
    2. Murray-Darling Freshwater Research Centre (MDFRC), Albury, NSW, Australia
    3. Present address: Russell J. Shiel, Department of Environmental Biology, University of Adelaide, Adelaide, SA, Australia
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  • John D. Green,

    1. Department of Biological Sciences, University of Waikato, Hamilton, New Zealand
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  • John D. Langley

    1. Biological and Environmental Sciences, Middlesex University, London, U.K.
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Margaret A. Brock, DLWC, PO Box U245, Armidale NSW 2351, Australia. E-mail: mbrock@dlwc.nsw.gov.au) or Daryl Nielsen, PO Box 921, Albury, 2640, NSW, Australia. E-mail: daryl.nielsen@csiro.au

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.

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