Aquatic ecosystems in arid environments are considered to be ‘islands of water in a sea of dry land’, providing important refugia and ‘stepping-stones’ of connectivity for aquatic fauna. Aquatic ecosystems in central Australia are vulnerable to degradation due to their natural isolation coupled with the impacts of invasive herbivores such as camels, which degrade small desert waterbodies through drinking, trampling, and by fouling with large quantities of dung. The objective of this study was to determine the impact of camels on arid zone aquatic ecosystems. To do this we experimentally assessed the impacts of camel dung on the water quality and macroinvertebrate colonization and community composition of arid zone freshwater pools.
Experimental mesocosms were used to imitate small arid zone waterbodies. Camel dung (2kg) was added to half the pools (the treatment), the remaining pools (without dung) acted as the controls. All pools were sampled weekly for water quality, nutrients, chlorophyll a and macroinvertebrate richness and abundance, over an eight week period during summer.
Significant negative effects of camel dung on water quality and macroinvertebrate colonisation and community composition were detected. Macroinvertebrate abundance was higher in control pools; treatment pools were favored by pollution tolerant taxa such as mosquito larvae and control pools were favored by sensitive taxa such as larval mayflies and larval dragonflies. 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.