TIDAL SYSTEMS WITH EXTENSIVE WETLANDS DOMINATE GREENHOUSE GAS EMISSIONS FROM AUSTRALIAN ESTUARIES

Estuaries play an important role in connecting the global carbon and nitrogen cycles of the land-to-ocean continuum. The amount of emitted estuarine greenhouse gases (GHG; CO₂ and CH₄) can be influenced by the geomorphology and magnitude of disturbance in the estuaries. Australia has over 1,000 estuaries along 38,000 km of coastline, of which 75% are classified as low or moderately disturbed. This makes Australia a good analogue for the ~34% of coastal regions classified globally as less than moderately disturbed (>40% intact). To assess Australia’s contribution to global estuary GHG emissions, water-air GHG fluxes from 36 measured and 11 published Australian estuaries were upscaled to 974 assessed estuaries in Australia, classified into three estuary types (lagoons, small deltas, and tidal systems) and four disturbance groups (low to very high). We found that the effect of disturbance on estuarine water-air GHG flux were strongly influenced by the geomorphic type of the estuaries. Although increasing disturbance correlated to increased emissions, its effect was less pronounced in tidal systems as compared to lagoons. However, annual GHG emissions from Australian estuaries were dominated by low and moderately disturbed tidal systems with extensive wetlands even though they had lower water-air CO₂ and CH₄ flux rates. This was due to their extensive distribution across Northern Australia. As such, estuarine geomorphology, which captures drivers like wetland extent, in combination with disturbance, should be considered in GHG emission estimates.

Presentation Preference: Oral

Primary Presenter: Jacob Yeo, Southern Cross University (jacob.yeo@scu.edu.au)

Authors:

Jacob Yeo, Southern Cross University  (jacob.yeo@scu.edu.au)

Bradley Eyre, Southern Cross University  (bradley.eyre@scu.edu.au)