The impact of a climate dryness on multiscale biodiversity of freshwater macroinvertebrates in wetlands on a salinized landscape

Sean Thomas Atkinson

Across the globe, Mediterranean climatic regions are shifting to more arid climatic conditions. Climate change affects wetland water regimes through increasing temperatures, decreasing rainfall volumes and timing, changing regional wind patterns and increased evaporation rates. Invertebrates that rely on wetlands risk local extinction unless they have adaptations that can withstand prolonged periods of desiccation. Consequently, prolonged drying, and its effects on physicochemical conditions has the potential to reduce wetland biodiversity. In particular, dryland salinisation will exacerbate salinisation of wetlands. In this study, my aims were to: 1) Determine whether wetlands in the Western Australian Wheatbelt and Great Southern regions showed impacts of climatic drying on wetland water regime and water quality between 1998 and 2011; 2) Determine whether the alpha (local), beta (between wetlands) and gamma (regional) diversity of wetland invertebrates changed over this 13 year period as climatic drying progressed; and 3) Characterize the distribution of aquatic macrophyte assemblages in these wetlands and associate these with patterns in dormant invertebrate assemblages. Aquatic invertebrates and water quality parameters were collected from 17 wetlands in the Wheatbelt and Great Southern regions of Western Australia between 1998 and 2011. Multivariate statistical analyses were used to identify changes in alpha, beta and gamma aquatic invertebrate diversity, and examine patterns in water quality data from 1998 to 2011. Sediment was collected from 12 wetlands and flooded for two months to record emergent invertebrates and germinating macrophytes. Climatic drying caused the 17 wetlands to decline in depth and frequency of dry periods increased. Gamma and alpha richness declined across time, but beta diversity (among wetlands) remained consistently high as each wetland retained a distinct fauna. Salinity and average rainfall partially explained invertebrate richness and assemblage composition in wetlands. The inundation experiment showed few germinating macrophytes or hatching invertebrates: assemblages were too depauperate to establish relationships with other variables. Results support the conclusion that Wheatbelt and Great Southern region wetlands experienced changes in aquatic invertebrate assemblages due to drying water regimes. Western Australia is in an advanced state of climate drying compared to other Mediterranean regions. The results of this study will inform other Mediterranean regions of the biodiversity outcomes of long-term dryness in wetlands with distinct fauna.

The impact of a climate dryness on multiscale biodiversity of freshwater macroinvertebrates in wetlands on a salinized landscape

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