Oral Presentation Australasian Groundwater Conference 2017

Compound specific isotope analysis – a new tool to assess groundwater ecosystem function (#239)

Alison Blyth 1 , Mattia Saccò 1 , Colin Smith 2 , William Humphreys 3
  1. Curtin University, Perth, WA, Australia
  2. Archaeology and History, Latrobe University, Melbourne, Victoria, Australia
  3. Zoology, Western Australian Museum, Perth, WA, Australia

Groundwater is a fundamental resource of global importance. The hydrology of Australia’s aquifers is relatively well studied, but far less understood are the ecosystems they contain1. To understand the effects on these systems of issues such as climate change, and water extraction, we need to understand how these ecosystems function. This is a challenging question, given that the systems are dominated by invertebrates living in highly cryptic environments.

To circumvent these problems, we are applying a combined programme of compound specific isotope analysis of single amino acids, and radiocarbon dating of fauna. This will allow us to: 

1)      Assign trophic position to different invertebrate species

2)      Identify the dominant carbon sources at the base of the subterranean food web

3)      Assess changes in these characteristics with fluctuations in physiochemical parameters

We can achieve this, even in small samples, because by analysing the isotopic composition of single amino acids, we can access signatures from different parts of the trophic process. By nitrogen isotope analysis of phenylalanine and glutamic acid we can assess the signature of the base of the foodweb and the trophic enrichment, giving relative trophic position2. For carbon isotopes differences seen between essential and non-essential amino acids and via pairwise analysis of particular compounds which allow the type of carbon source at the base of the system to be indicated. This is enhanced by companion radiocarbon analyses, indicating the degree of carbon recycling vs fresh carbon being utilised in the food chain.

The application of cutting edge chemical techniques has particular value if combined with biological and physiochemical techniques to provide a “whole system” picture3. This will allow a much fuller understanding of how these cryptic ecosystems function, and a much stronger ability to assess their fragility or resilience under different natural and anthropogenic pressures.

  1. Humphreys W. F. 2006. Aquifers: the ultimate groundwater-dependent ecosystems. Australian Journal of Botany54, 115–132.
  2. Chikaraishi Y, Ogawa N. O., Kashiyama Y., Takano Y., Suga H., Tomitani, a., Miyashita, H., Kitazato, H. & Ohkouchi, N. 2009. Determination of aquatic food-web structure based on compound-specific nitrogen isotopic composition of amino acids. Ecol Res 7: 740–750.
  3. Humphreys, W. F. 2009. Hydrogeology and groundwater ecology: Does each inform the other?. Hydrogeology Journal, 17(1), 5-21.
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  • We are offering awards for Career and Early Career presentations and posters. Please indicate length of time since highest degree completed.: 5 Years or more