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Microrefuges from drying for invertebrates in a seasonal wetland

Strachan, S.R., Chester, E.T. and Robson, B.J. (2014) Microrefuges from drying for invertebrates in a seasonal wetland. Freshwater Biology, 59 (12). pp. 2528-2538.

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Seasonally intermittent freshwater environments show large temporal changes in area and environmental conditions (which may be harsh). We investigated whether microhabitats that retain moisture could provide a refuge during drying in a seasonal wetland. We investigated occupancy by invertebrates of three potential microrefuge types: surface depressions, shallow cracks and deeper fissures in the sediment of a wetland in Western Australia. Our aims were to determine whether the assemblages occupying these microrefuges differed and whether they changed as the wetland dried and reflooded. Ten microrefuges of each type were sampled for invertebrates, sediment and temperature during each of three hydrological phases: the damp phase (surface water absent but sediment moist), the dry phase (groundwater at its lowest level) and the reflooded phase (surface water present). Sediment samples taken from each microrefuge in the damp and dry phases were reflooded in the laboratory to reveal species aestivating or present as eggs, and sediment organic matter content was measured. Sediment organic matter content did not change between wetland phases. The invertebrate assemblage in the microrefuges showed almost complete species turnover between phases. Invertebrate composition differed between microrefuges, and temperature in the deeper fissures was on average >10 °C lower than in surface depressions and shallow cracks. Microcrustaceans and gastropods survived the drier months as resting stages in the microrefuges and either emerged or hatched from eggs upon reflooding. Several species, including isopods and caddisflies, were collected only from cracks and fissures as the wetland dried. During drying, a high diversity of carnivorous species was observed in the microrefuges. Sediment microrefuges apparently underpin resistance to drought by invertebrates in South Lake. Those species that depend on sediment fissures to survive may be threatened by the declining groundwater table in the region. Changes to wetland hydrology and other human activities that affect wetland sediment or vegetation will affect the range of microrefuges available to invertebrates to survive drying and may thus alter wetland biodiversity.

Item Type: Journal Article
Murdoch Affiliation(s): School of Veterinary and Life Sciences
Publisher: Blackwell Publishing Ltd
Copyright: © 2014 John Wiley & Sons Ltd
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