The impacts of an invasive herbivore (Camelus dromedaries) on arid zone freshwater pools: An experimental investigation of the effects of dung on macroinvertebrate colonisation

Aquatic ecosystems in arid environments provide important refugia and 'stepping-stones' of connectivity for aquatic fauna. Aquatic ecosystems in central Australia are vulnerable to degradation due to the impacts of invasive herbivores such as camels, which degrade small desert waterbodies through drinking, trampling, and fouling with dung. In this study we assessed the impacts of camel dung on the water quality and macroinvertebrate colonization and community composition of small arid zone freshwater pools using experimental mesocosms.Camel dung (2kg) was added to half the mesocosms (the treatment), the remaining mesocosms (without camel dung) acted as the controls. All mesocosms were sampled weekly for water quality, nutrients, chlorophyll a and macroinvertebrate richness and abundance, over an eight week period during summer.Macroinvertebrate abundance was higher in the control mesocosms in comparison to the treatment mesocosms. Pollution tolerant taxa such as mosquito larvae were common in treatment mesocosms, while sensitive fauna, such as larval mayflies and dragonflies were more common in the controls. The latter are predators and appeared to have a major influence on community composition.Our results reinforce the need for active management of invasive herbivores to protect aquatic biodiversity and to manage potential disease-vector species in central Australia waterbodies.