Thesis
Multidecadal changes in the benthic macroinvertebrate assemblage of the Swan-Canning Estuary
Masters by Research, Murdoch University
2025
Abstract
Climate change is impacting estuaries worldwide and those in microtidal regions with Mediterranean climates, such as in south-western Australia, are particularly vulnerable. Reduction in rainfall and thus streamflow in these estuaries has led to marinization, and population growth and intensification of land use can act synergistically and increase stressors. This study on the highly urbanized Swan-Canning Estuary investigated spatial and seasonal trends in the benthic macroinvertebrate community sampled seasonally in 2023/4 and made quantitative comparisons to data obtained using the same experimental design in 1986/7 and 2003/4. A total of 6,338 benthic macroinvertebrates, representing 48 taxa were recorded in 2023/4, with species richness, total density and community composition differing among sites and seasons. Contemporary analysis revealed a reduction in species richness and abundance from spring to autumn, likely due to freshwater flow. Inter-site variation in community composition could be attributable to the varying habitats present at each site. Comparisons to historical data revealed multiple lines of evidence of the effects of climate change and degradation. Species accumulation curves demonstrated that species richness had increased markedly in the current study, potentially driven by sustained high salinities that favour marine species. There was a 50% decline in the abundance of crustaceans, which are sensitive to environmental stress and a contemporaneous increase in more tolerant molluscs and highly tolerant annelids across the three decades. Furthermore, values for two metrics of ecosystem health, i.e. BOPA and qualitative taxonomic distinctness, changed in ways reflecting poorer environmental conditions. There was also a shift in species compositions, including the reduction and/or absence of several estuarine species (i.e. habitat compression), and an increase in the abundance of marine species, including the non-indigenous Batillaria australis and Caprella scaura. The findings of this study are likely highly applicable to nearby estuaries like the Peel-Harvey, and other urbanised estuaries in Mediterranean climatic regions. Moreover, the results showcase the value of historical data sets in understanding how increasing anthropogenic influences alter the biotic composition and health of estuaries and that regular monitoring should be conducted in major systems even on a decadal frequency.
Details
- Title
- Multidecadal changes in the benthic macroinvertebrate assemblage of the Swan-Canning Estuary
- Authors/Creators
- Ruth Lim
- Contributors
- James Tweedley (Supervisor) - Murdoch University, Centre for Sustainable Aquatic EcosystemsEssie Rodgers (Supervisor) - Murdoch University, School of Environmental and Conservation SciencesKerry Trayler (Supervisor)
- Awarding Institution
- Murdoch University; Masters by Research
- Identifiers
- 991005795472707891
- Murdoch Affiliation
- School of Environmental and Conservation Sciences; Centre for Sustainable Aquatic Ecosystems
- Resource Type
- Thesis
- Note
- Accelerated Research Masters with Training at Murdoch University
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