Oral Presentation Australian Society for Limnology Congress 2013

Microrefuges for invertebrates in a wetland in response to drying. (#11)

Scott R Strachan 1 , Edwin T Chester 1 , Belinda J Robson 1
  1. Murdoch University, Murdoch, WA, Australia

Seasonally intermittent freshwater environments show enormous temporal changes in habitat area, ranging from extensive surface water and relatively constant environment in winter to a dry, hostile even desiccated environment in summer. Invertebrates respond to adverse conditions through physiological adaptations and behavioural responses and may use these traits to retreat into microrefuges in the substrate when wetlands dry. This study examined the responses of invertebrates to drying within a wetland to identify microrefuges and their invertebrate occupants. We sampled from three potential microrefuges: surface depressions, shallow cracks and deeper fissures in the substratum of South Lake on the Swan Coastal Plain, Western Australia. Ten microrefuges of each type were randomly selected and sampled at each of three times during summer-autumn: as the wetland dried, during the dry period; as the wetland refilled to observe patterns of faunal occupancy. A was a large change in species richness was observed over the drying and reflooding cycle corresponding to changes in habitat area and physicochemical conditions.

Macroinvertebrate composition differed between microrefuges, the largest effect was turnover of species between times. Sediment organic content did not differ between times, but temperature and water content differed strongly between times across the three microrefuges. Many insects completed their aquatic stage and emerged as aerial adults before the wetland reflooded, whereas most of the crustaceans survived the drier months as resistant forms, and hatched out after the reflooding. Small scale habitat variability is important providing microrefuges for the survival of macroinvertebrates in this increasingly dry climate.