What is changing the pH of Australian estuaries?

Supervisory Team:

Primary supervisor: Andrew Fischer – IMAS Newnham

Co-supervisor: Darren McPhee – TEER NRM-North

Additional supervisors: Ed Forbes – NRET Hobart

Brief project description:

In recent decades, long-term monitoring programs have been able to establish clear evidence of the impacts climate change is having on Australian estuaries. Recent studies have identified that climate change impacts are highly dependent on the morphology of the estuary, showing variability in the severity, rate and trajectory of change for different water quality parameters, including physical changes such as sea level rise (Palmer et al. 2018). Water bodies such as rivers and lagoons with shallow average depths are suggested to be most at risk of increasing water temperatures and increasing levels of acidity.

In many large estuaries, anthropogenic CO2-induced acidification is enhanced by strong stratification, long water residence times, eutrophication, and a weak acid–base buffer capacity. Factors that lead to increased acidification can include (but are not limited to):

• coastal upwelling;
• river–ocean mixing;
• air–water gas exchange;
• biological production and subsequent aerobic and anaerobic respiration;
• calcium carbonate (CaCO3) dissolution; and
• benthic inputs

In the kanamaluka / Tamar estuary, long term measurements of pH in the upper estuary have been observed to consistently decline, becoming more acidic most notably in the upper estuary. While it is acknowledged that several environmental factors can influence changes in pH (and other water quality parameters), such as freshwater inflows and acid sulfate soils, it is important to recognise that climate change is a major factor that influences water quality and acidity, and which will continue to play a significant role in water quality and ecosystem health into the future.

The aim of this research is to conduct preliminary investigations to determine the potential causes of increasing acidity in the upper kanamaluka / Tamar through supervision of an Honours student project. It is proposed that a student undertake a literature review to identify all possible causes of acidification of estuaries at a broad and local scale. This review will be complimented by a statistical analysis and spatial modelling exercise of TEER water quality data an associated catchment spatial data. This would provide a starting point to understanding the drivers of changing pH and potentially eliminate some of the possible contributors.

An additional stipend is available for this project.

Skills students will develop during this research project:

• Developing conceptual models and then appropriate spatial and statistical models to understand drive of pH increase within the Tamar estuary.
• Creating, understanding and communicating the spatial model outputs
• Understanding resource management need, communicating with resource managers, public and other stakeholders, to ensure results are correctly conveyed.