Bulletin

Issue: July 2004

Research

'Barcoding' bloodworms to fight water pollution

La Trobe researchers are developing DNA techniques to help Melbourne Water assess how effectively it cleans up polluted creeks.

The work focuses on bloodworms, the larvae of a highly diverse group of non-biting midges known as chironomids, which occur all over the world. In Europe and North America they are used as indicators of the health of waterways.

'Chironomids live throughout their larval stages in sediments, and are therefore closely associated with any sort of pollutant or toxicant that might be in the sediment or the overlying water,' says Dr Yvonne Parsons of the University's Centre for Environmental Stress and Adaptation Research (CESAR).

Different species of bloodworms are susceptible to different levels of pollutants, so the array of species present in an area provides an indication of which pollutants are there, and at what concentrations.

'But the differences between individual species can be very, very minute,' says Dr Parsons. 'And it takes a lot of expertise to be able to identify them.'

So her research team has taken a molecular approach - the first time this has been done worldwide - to distinguish between the nine southeast Australian species of the genus Chironomus. The researchers have concentrated on a particular region of the gene for the enzyme Cyctochrome Oxidase 1.

This region, which diverges rapidly between species, is increasingly being used for classification purposes. In fact, some researchers in Canada now refer to it as 'the barcode of life'. The DNA identification of bloodworms is working 'very nicely', Dr Parsons says.

In collaboration with Melbourne Water scientist, Vin Pettigrove, the researchers hope to develop ways of using bloodworm diversity to determine the impact of water management practices.

'One of the big problems of remediation of polluted areas is that the management authorities do not have a very good sense of what particular action is going to be most beneficial,' Dr Parsons says. 'Bloodworms and other bio-indicator species enable us to get a handle on the effect pollutants are having on actual life forms. You can have a high concentration of a particular heavy metal in the sediment, for instance, but it might not be having much impact because it is in a form which is non-toxic.'

Dr Parsons, however, wants to go further. She is working with geneticist Dr Jon Martin of Melbourne University to identify the genes associated with pollution tolerance in the chironomids. The pair think they may then be able to develop an assay of the activity of particular genes which will indicate which pollutants are present and their impact.

'If a particular pollutant has a negative effect, certain genes should be expressed more heavily to try to reduce that effect,' Dr Parsons says. Research by PhD student Jacqueline Ward indicates that local adaptation to pollution occurs in some chironomid species and gene expression in these populations can be tested.

But that's not all. Dr Parsons thinks that these negative effects should be felt sooner by microbes than by insects. So she is also working with microbial geneticist Associate Professor Harold Stokes of Macquarie University investigating the genes which confer heavy metal tolerance in micro-organisms.•

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