Associate Professor Damien Maher
Alkalinity Production by Coastal Vegetated Habitats
Coastal vegetated habitats (mangroves, saltmarshes and seagrasses) are sites of intense carbon fixation, respiration and organic matter burial. As a result, these areas also generate significant amounts of alkalinity through anaerobic respiratory pathways. This alkalinity production can then exported to the coastal zone where it may provide a buffering effect against coastal acidification. However to date there is only one "back-of-the-envelope" calculation of alkalinity production and export from coastal vegetated habitats. Our preliminary observations suggest this estimate may be an order of magnitude to low, and that alkalinity exports from coastal vegetated habitats may produce a measurable buffering effect in coastal waters tens of kilometres offshore. I am currently working on constraining the rates, drivers and pathways of alkalinity production and export from coastal vegetated habitats with colleagues from SCU (Prof Johnston, Prof Santos, Dr Sanders, Dr Tait), Deakin University (Dr Macreadie), and a number of international collaborators.
Coastal Greenhouse Gas Dynamics
The coastal zone plays a disproportionately large role in the cycling of the three dominant greenhouse gases; carbon dioxide, methane and nitrous oxide. However, our understanding of the processes, pathways and rates of greenhouse gas production and consumption in these biogeochemical hot spots remains incomplete. This is due predominantly to the large spatial and temporal variability within these systems, and the hitherto lack of suitable sensors for measuring high resolution, high precision gas concentrations and stable isotope ratios in situ. We are currently using cutting edge laser spectroscopic techniques to overcome these issues to assess the role of the coastal aquatic and terrestrial zones in global greenhouse gas cycling. The results will feed into to global biogeochemical models to help elucidate current and future feedback mechanisms associated with anthropogenic and natural climate change.
The Export of Terrestrial Carbon Via Groundwater
Rivers and estuaries are often supersaturated in CO2 and traditionally this has been linked to export of organic carbon from terrestrial environments, which is respired within the aquatic environment. However, groundwater is often enriched in dissolved carbon and 1 - 2 orders of magnitude higher in pCO2 than surface waters, therefore groundwater inputs can have a significant influence over surface water pCO2 and dissolved carbon concentrations. A portion of this groundwater carbon is derived from terrestrial subsurface respiration, which is not accounted for in terrestrial carbon budgets which are normally based on measurements of CO2 above the soil surface (e.g. eddy covariance and chamber incubations), and therefore tend to neglect subsurface pathways. I am currently working on a number of projects looking at the magnitude of the groundwater carbon input to aquatic systems and the transformation pathways of this carbon with a ultimate goal of determining how this pathway should be integrated into the global carbon cycle.
The "Missing Mangrove Carbon"
Mangroves are ecologically important, productive and extremely carbon rich habitats, that dominate the coastal zone in subtropical and tropical latitudes. In spite of the obvious importance of these habitats, there is still a paucity of data on many of the carbon cycling processes within these systems. One such information gap is evident by the unbalanced global mangrove carbon budget, with more than half of the carbon fixed through primary production unaccounted for. This is the stimulus for one component of the research that I have been carrying out, with initial results indicating that this "missing" carbon maybe dissolved inorganic carbon, derived from subsurface respiration, which is subsequently exported through the groundwater pathway (Maher et al, 2013 Limnology and Oceanography).
Integrated Carbon Monitoring System Development
I am also working on an integrated dissolved carbon monitoring system that will autonomously monitor the various dissolved carbon pools including; dissolved organic carbon (DOC), dissolved inorganic carbon (DIC) and volatile organic carbon (VOC). This work stems from the need to better understand the pathways and cycling processes of carbon in the coastal zone, and follows on from the success we have had with a coupled radon/pCO2 system (Santos, Maher and Eyre, 2013, Environmental Science and Technology) for investigating the role of groundwater in driving pCO2dynamics in rivers and estuaries, and a Cavity Ring Down Spectroscopy system for determining aquatic carbon cycling pathways (Maher et al., 2013 Environmental Science & Technology).
Traditional methods (e.g. benthic cores and chambers) have inherent artefacts that may lead to inaccuracies in benthic flux calculations. Eddy correlation is a relatively new method for measuring benthic fluxes, which eliminates many of the artefacts associated with traditional techniques. We have two eddy correlation systems, which we are currently using to investigate benthic oxygen fluxes in a range of complex coastal habitats.
Coal Seam Gas and the Environment
A massive growth of the coal seam gas industry has occurred in NSW and QLD in the last decade. Even faster growth rates are predicted for the next decade. However, our basic understanding about the influence of CSG mining on the environment remains very limited.
In addition, fugitive greenhouse gas emissions from CSG fields have not been investigated in Australia yet. We recently made a submission to the government reporting the first, but still very preliminary, observations of greenhouse gases in the atmosphere of an Australian CSG field. Our submission has generated intense debate in the media:
Gas Leak, Four Corners, April 1 2013
Research questions green credentials of CSG, ABC 730, November 14 2012
Methane leaking from coal seam gas field, testing shows, Sydney Morning Herald, November 14 2012
Newman concerned by CSG methane report, The Australian, November 15 2012
Elevated atmospheric methane found on QLD gas field, ABC World Today, November 15 2012
Our group has the expertise and cutting edge technology to assess greenhouse gases in water and the atmosphere of CSG fields. We recently obtained a large infrastructure grant from the Australian Research Council that puts us in an excellent position to fill some of the major emerging knowledge gaps.
Major research grants
- $436,000 (DP180101285) Beyond burial: Redefining the blue carbon paradigm.
- $360,000 (DE150100581) Resolving the role of aquatic ecosystems in processing and degassing terrestrially fixed carbon.
- $600,000 (LP160100061) Maximizing carbon sequestration in freshwater wetlands.
- $900,000 (LP150100519) Unravelling the drivers of greenhouse gas emissions in estuaries. 2015 to 2018.
- $150,000 (LE140100083) - "A gamma spectrometry facility for cutting edge environmental geochemistry investigations" 2014. CI 3 of 5.
Other Category 1 Grants
- $18k AINSE Grant no. ALNGRA15507 Are mangrove carbon exports, old or modern? A C-14 analysis of particulate organic carbon (POC), dissolved organic carbon (DOC), and dissolved inorganic carbon (DIC).
- $9300 AINSE Grant no. ALNGRA14015 Are mangrove carbon exports, old or modern? A C-14 analysis of particulate organic carbon (POC), dissolved organic carbon (DOC), and dissolved inorganic carbon (DIC).
- $5400 AINSE Grant no. AINGRA07045 - Sedimentation rates in three NSW estuaries.
- $83,000 Is groundwater the missing source of nutrients driving eutrophication in the Great Barrier Reef. 2016-2018 Hermon Slade Foundation.
- $270,000 "Extension- Increasing carbonate chemistry data for the Great Barrier Reef". 2014/2015 to 2015/2016 Great Barrier Reef Foundation.
- $125,240 Assessing groundwater recharge and flow paths in the Woodburn Sands aquifer using modelling and geochemical approaches. RMS
- $300,000. "A carbon budget for the Great Barrier Reef". Great Barrier Reef Foundation. 2013/2014. CI
- $400,000. "Increasing carbonate chemistry data for the Great Barrier Reef".2013/2014 to 2014/2015. CI
- $30 000 ($15 000 NOROC, $15 000 SCU) - Preliminary assessment of groundwater and creek water chemistry in CSG exploration areas of the Northern Rivers Region.
- $24 000 "Do residential canal estate developments increase greenhouse gas emissions from Australian estuaries". CI 2 of 2 Funding agency: Australian Academy of Science WH Gladstone's Population and Environment Fund. 2 Years.
- $18,080. "Is groundwater discharge a major source of nutrients and eutrophication to Brisbane Water?" - CI 1of 3. Gosford City Council. 2012-2014.
- $50,000 "Benthic habitat mapping and primary productivity measurements in the Hastings River and Camden haven estuaries." Port Macquarie Hastings Council.