Occurrence of aquatic invertebrates of the wheatbelt region of Western Australia in relation to salinity

Abstract

The wheatbelt region of Western Australia has been extensively cleared of indigenous vegetation for agriculture and is now severely affected by dryland salinity. Wetlands that were once freshwater are now saline and others are under threat, as are the animals and plants that inhabit them. Rising groundwater is also affecting the many naturally saline playas. To provide a framework for setting conservation priorities in this region a biological survey was undertaken, including sampling of aquatic invertebrates at 230 wetlands. In this paper, we have used data from the survey to summarise occurrence of species in relation to salinity. Total species richness at a wetland showed no response to salinity below 4.

Salinity as a driver of aquatic invertebrate colonisation behaviour and distribution in the wheatbelt of Western Australia

“…Anthropogenic (secondary) salinisation of arid and Mediterranean lands occurs globally and influences the distribution of aquatic assemblages across the landscape (Roberts & Irving-Bell, 1997;Halse et al, 2003;Hart & Lovvorn, 2005;Pinder et al, 2005;Piscart et al, 2005b). General consensus exists that increasing river and wetland salinity has potential to cause local extinctions, alterations in ecosystem function and extensive environmental damage (Halse et al, 2003;Kefford et al, 2003;Jardine et al, 2007).…”

“…General consensus exists that increasing river and wetland salinity has potential to cause local extinctions, alterations in ecosystem function and extensive environmental damage (Halse et al, 2003;Kefford et al, 2003;Jardine et al, 2007). Halse et al (2003) predicted that approximately one-third of aquatic invertebrate diversity in the inland southwest of Western Australia (WA) will disappear with the expansion of secondary salinisation, and Pinder et al (2005) suggested that up to 100 species that are largely restricted to the inland southwest are at risk of extinction. However, biotic factors, such as behaviour, are also important drivers of organism distribution, but considered less frequently (Stoks & McPeek, 2003;Blaustein et al, 2004).…”

“…Studies have found a range of invertebrate fauna, such as the disease vector Ae. camptorhynchus, to be prevalent in saline areas (Pinder et al, 2005;Jardine et al, 2007;Lindsay et al, 2007). However, little attention has been given to the significance of colonisation behaviour in distribution (but see, Silberbush et al, 2005).…”

“…Inconsistencies between laboratory and field results undoubtedly result from additional biotic and abiotic inputs (such as predation, competition, microhabitat structure, habitat availability and stochastic encounters with water bodies). As such, patterns in assemblages of colonisers across a salinity gradient may be more holistically informative of how salinity influences colonisation behaviour, in the presence of other variables, than individual taxa alone Pinder et al, 2005). Additionally, analyses of assemblages enable the relative contributions of fresh water and halophilic fauna to be readily quantified.…”

“…As such, it was expected that most aquatic fauna of mesocosms would be freshwater taxa. Dispersal of aquatic insects in the wheatbelt is widespread, but locally heterogeneous, due to variation in habitat (Kay et al, 2001;Pinder et al, 2005). It is anticipated that insects colonising mesocosms vary in space and time.…”