Macroinvertebrate cycles of decline and recovery in Swan Coastal Plain (Western Australia) wetlands affected by drought-induced acidification

Abstract

Management of wetlands influenced by the Gnangara groundwater mound, Western Australia, is becoming increasingly challenging due to an ongoing decline in the regional groundwater table. A number of these groundwater-dependent wetlands have acidified (with adverse effects on the extant macroinvertebrate fauna) due to the oxidation of pyritic sediments. One management option in such cases is artificial augmentation of surface water in order to maintain or reinstate anaerobia in the sediments. This paper documents cycles of macroinvertebrate decline and recovery over 12 years of monitoring in three Gnangara mound wetlands affected by drought-induced acidification, one of which is being artificially augmented. Acidification did not result in a reduction of the total number of macroinvertebrate families present, however, there were clearly identifiable groups of acid-sensitive taxa (amphipods and isopods, ostracods, chydorid and daphnid cladocerans, mayflies, oligochaetes, clams and snails) and acid-tolerant taxa (sandfly larvae, macrothricid cladocerans and water boatmen). In the artificially augmented wetland, the effects of acidification were reversed: acid-sensitive taxa reappeared and acid-tolerant taxa decreased in numbers.Moreover, there were a number of taxa that appeared for the first time since augmentation, and summer family richness increased markedly. This study has shown that artificial augmentation of wetland water levels can be a successful recovery strategy for recently acidified systems, but this will depend on a number of factors, and the 'recovered' state will be at least slightly different from the original state.

Alterations in the macrobenthic fauna from Guadarranque River (Southern Spain) associated with sediment–seawater acidification deriving from CO2 leakage

“…This result, showing the isopod C. carinata as the species with the highest differences between pH treatments, is according Sommer and Horwitz (2009) who identified the isopod (as taxonomic group) as one of most acid-sensitive aquatic macroinvertebrates. These authors argued that this is due to respiratory and ion-regulatory failure, and probably to possessing a calcified exoskeleton, as well.…”

“…However, despite no literature was found about the amphipod J. marmorata, Haunton et al (2009) reported no significant difference in the percent of mortality in the amphipod Gammarus locusta exposed to different pH levels (from 8.1 to 7.6), defending the hypothesis that this is a robust species. Therefore, our results are according to Sommer andHorwitz (2009), Wood et al (2014), Ferreira et al (2004) and Haunton et al (2009).…”

Macroinvertebrate traits distinguish unregulated rivers subject to water abstraction

“…Many studies have reported that such taxa are sensitive to changes in water quality, particularly those induced by drought and dry conditions (Heino 2005, Bowman et al 2006, Miller et al 2009, Sommer and Horwitz 2009. Tolerant families in edges generally respire through their teguments, and a greater prevalence of taxa with tegument respiration typifies areas with modified flow regimes and other human perturbations (Charvet et al 2000, Tomanova et al 2008.…”

Disentangling the Complexity of Groundwater Dependent Social-ecological Systems

“…The lowered groundwater levels have also contributed to the acidification of several wetlands in the area through the exposure of acid sulphate soils. Artificial maintenance of water levels has been shown to restore some of the impact of droughtinduced acidification on macroinvertebrate communities but change the seasonal hydrological regime of the wetlands (Sommer and Horwitz 2009).…”