ANSTO's research capabilities, led by the OPAL nuclear research reactor and associated instruments provide access to users investigating areas as diverse as materials, life sciences, climate change and mining/engineering.
Aquatic Ecosystems
Shortcuts:
- Stable isotope applications in aquatic ecosystems
- Radioecology
- Collaborations
- Key facilities and instruments
- Publications
- Team members and contacts
Using isotopes to evaluate how freshwater ecosystems function
Aquatic ecosystems, including rivers and wetlands, are complex systems with numerous dynamic relationships between water, earth, air, plants and animals. Water is a vital resource that is under ever-increasing demand from population and industry growth, agricultural development and environmental allocations that are crucial in sustaining the natural ecosystems upon which we all rely.
Nuclear techniques including accelerator mass spectrometry, radiotracing and stable isotope-ratio mass spectrometry provide unique benefits in the study of freshwater ecosystems, and are utilised by ANSTO's Aquatic Ecosystems group to better understand their complex nature and inform decisions for water use.
Stable isotope applications in aquatic ecosystems
| Proportions of heavy isotopes (13C and 15N) increase progressively up the food chain (ref: Carol Kendall US Geological survey). |
A key tool utilised at ANSTO is the measurement of the natural abundance of stable isotope ratios (ratio of heavy to light stable isotopes for any element) to determine food web structures, to track changes in ecosystems over time, and to understand the cycling of nutrients and pollutants through aquatic ecosystems.
The isotopic composition of living organisms is a reflection of their nutrition source. The level of enrichment of the heavier 15N to 14N atoms tells the researchers the trophic level (place in the food chain)of specific organisms, while the carbon isotopes indicate what plants or prey the organism is consuming.
The ratios of isotopes may vary or change in nature due to physical, chemical and biological processes. Important applications include tracking how these isotope ratios change within animal and plant populations, which can provide valuable insights as decisions are made about the use and protection of Australia's waterways.
Stable isotope ratios of carbon and nitrogen in most organisms will reflect diet shifts in response to, for example, water availability changes or the availability of new nutrient sources that may be the result of altered management practices.
The same isotopes can help the researchers to examine animal migration and movement, as well as changes in age and size ranges in populations. They can also identify where animals have come from, such as from wild versus aquaculture production.
Stable isotope ratios can also reveal how much transpiration, compared with evaporation is occurring in wetland vegetation, how much floodwater infiltrates the soil, and from which depths in the soil the wetland plants are obtaining their water. This information is important when water for the environment is scarce, and decisions must be made about how much water needs to be allocated to sustain our vital wetlands.
Radioecology
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| Freshwater prawns Macrobrachium australiense eating radio-labelled sediment to determine how much metal the prawn accumulates from diet. |
ANSTO uses specialised equipment that can detect a wide range of isotopes, including natural or man-made radioisotopes. Radioactive isotopes have a number of different advantages compared to stable isotopes for biological studies.
These kinds of isotopes can be tracked as plants take up minerals and nutrients from soil and water and as animals eat plants. By tracking the course of these tracers, much is revealed about how plants and animals function, and relate to one another.
Radioisotopes are also particularly helpful in studies on the nature of pollution. For example, how heavy metals such as cadmium, zinc and cerium move through aquatic systems and how they bioaccumulate. Many of Australia's wetlands and sediments already contain these metals and ANSTO's studies can help establish under what conditions they will remain in place or become mobile.
Collaborations
| Collaborative field sampling in the Yanga wetlands of NSW |
Key collaborations include participation in International Atomic Energy Agency (IAEA) programmes including the Environmental Modelling for Radiation Safety (EMRAS I and II) and Modelling and Data for Radiological Impact Assessments (MODARIA) which coordinate modelling of biological uptake and doses from radionuclides.
Staff also provides expertise in support of the Marine Benchmark Study on the Possible Impact of the Fukushima Radioactive Releases in the Asia-Pacific Region IAEA/RCA Project RAS/7/021).
Australian research locations include the Macquarie Marshes in central-west NSW, the Gwydir wetlands in north-west NSW, and Yanga, located on the Lower Murrumbidgee River floodplain in south-western NSW. In addition to their importance to Australia, these wetlands have international recognition under the Ramsar Convention treaty which recognises and seeks to maintain the ecological character of wetlands of international Importance.
Key aspects of our research are performed in collaboration with the NSW Department of Environment and Heritage, NSW department of Primary Industries (Fisheries), the CSIRO, the University of New South Wales, and the University of Wollongong, among others.
Key facilities and instruments
| Cherax destructor (yabbies) and Macrobrachium freshwater prawn are being raised determine the metal accumulation rates as well as how stable isotopes respond to diet changes that can occur due to seasonal fluctuation or events such as floods. |
The team has a range of laboratory capabilities including a controlled aquarium room used for studying plants, arthropods and fish. Current research includes raising a group of yabbies to determine effects of food selection differences that often occur in the real world as a consequence of seasonal changes, or events such as floods.
Other laboratories include a climate-controlled greenhouse designed for the use of radiotracers that provide researchers with insights into how wetlands cycle nutrients, metal and radionuclides. The team are using stable isotopes to study how the trees use water under certain stressors such as increased salinity and reduced water availability.
| River Red Gum eucalypt trees in the temperature controlled greenhouse. The team are using stable isotopes to study how the trees use water under crtain stressors such as increased salinity and reduced water availability. |
| Live-organism gamma spectroscopy |
Isotope Ratio Mass Spectrometry (IRMS) is used to measure stable isotope ratios in the ecological samples collected by the team. Mass spectrometry relies on differences between the mass of stable isotopes to separate them during the analysis process.
ANSTO has a range of gamma spectroscopy instruments, some with extremely low levels of detection. Also available within ANSTO's Institute for Environmental Research are Accelerator Mass Spectrometry (AMS), alpha spectroscopy, and Ion Beam Analysis (IBA) capabilities which present detailed isotopic and materials analysis.
Publications
A list of current publications can be found here:
Team members and contacts
Dr Mat Johansen, Radioecology
T: +61 2 9717 3060
E: Mathew.johansen@ansto.gov.au
Dr Debashish Mazumder, Stable Isotope Ecology
T: +61 2 9717 9219
E: Debashish.mazumder@ansto.gov.au
Dr Suzanne Hollins, Isotope Hydrology/Ecohydrology
T: +61 2 9717 3701
E: Suzanne.hollins@ansto.gov.au
Dr Tom Cresswell, Isotope Ecology, metals in aquatic systems
T: +61 2 9717 9412
E: Tom.cresswell@ansto.gov.au