Could the study of insect DNA save Australia's streams?

The Age 28 Sep 10;

INSECTS may be small but something microscopic — the DNA of the insect — is set to play a big role in helping scientists isolate the impact of pollution on urban streams.

Bio21 Institute research fellow Melissa Carew is part of a Melbourne research team developing cutting-edge molecular tools to more easily identify aquatic insect species.

In turn, she says, the "molecular biosignatures" of aquatic macroinvertebrates will help Melbourne Water and the Environment Protection Authority — partners in the research — apply better remedies to pollution, faster. And it will mean less taxing work for taxonomists.

How are aquatic ecosystems under increasing threat by human activities?

In Melbourne, thanks to urban sprawl, there's a major problem within catchments because the modified environment has a large effect on our streams. Habitat is being destroyed around streams and there are increased loads of pollutants going into them from industrial and residential estates: nitrogen from fertilisers used in gardens, zinc from zinc-aluminium roofs on large sheds and chemical run-off from roads.

And the threat is exacerbated by climate change?



With drought we have reduced water flows, so our streams become more stagnant and more sediments and toxicants build up. There are predictions that there will be much less rainfall in south-eastern Australia — and that will reduce flows further.

How do you measure aquatic pollution?



The condition of aquatic macroinvertebrates — all the insects, crustaceans, molluscs and worms that live in the streams — plays a major part in the monitoring that's done around Australia. But currently, because insects are so difficult to identify, we tend to use them at the family level. If we can identify them at a lower taxonomic level — such as species — we can get a lot more information.

What approach are you working on?

We're using DNA techniques to create a "DNA barcode" for each species. So rather than have a person look down a microscope and look for the number of hairs on the back of an animal, or little structures that are very similar in species, you can reduce it down to a DNA sequence, which would then be specific to a group of species. It means we can avoid having to spend months sitting at microscopes with experts in these insect groups — simply by taking a sample of these animals from the environment and then isolating their DNA and, potentially, going through and pulling out the DNA barcodes.

What happens once you know which species are present at a site?

We link that back to the ecological and pollution-sensitivity information we have about those species, and make an assessment of that environment.

So you combine the DNA approach with a field-based microcosm method?



Yes. That's what we're using to try to develop a lot of the "biosignatures". We're exposing animals — using these microcosms — to different kinds of pollutants, to build up a profile of those animals, and what categories of pollution they're tolerant or sensitive to.

So it's all about identifying insect indicator species?



That's correct. In aquatic environments, we could literally have thousands upon thousands of different species, but only some of those animals will be really good as indicators.

Industry must be keen on this work.

Well, rather than just being able to say something's good or bad, we can actually say what the problem is — so if it is a pollution problem, then management agencies can target their response. For instance, Melbourne Water could put in wetlands to help remove a nitrogen problem. If it's a heavy metal problem, it may put in a treatment plant on the stormwater drain to remove all the metals before they're deposited in the creek.

DEB ANDERSON