Iron bacteria are organisms that obtain their energy by oxidising dissolved ferrous iron into insoluble ferric iron (rust) and deposit it in the slimy, jelly-like material that surrounds their cells. The result of this process is the rust coloured deposits and surface sheen you may have noticed.

This process is natural in the upper reaches of fresh water creeks and stagnant water bodies, and does not usually pose any environmental harm or risk.

Where am I most likely to see iron bacteria?

• On rocks near waterfalls
• Where sandstone has been crushed and used as fill for roads etc.
• On steep slopes where water seeps out of the ground
• Creeks that are fed by groundwater (water flowing under the surface)

Making sure it's iron bacteria

There are a couple of things you can do to make sure what you are looking at is iron bacteria, and not a pollution incident

• Smell test - It is possible that you will smell something like decaying matter in a swamp. This is fine, it is just likely that the bacteria are dying (especially if they are being dried out by the sun). It shouldn't smell toxic like petrol, oil, chemicals or sewage.
• Surface test - It is possible that you may notice something that resembles oil on top of the water, in the same location as the rust-coloured material. If you poke a stick into the surface and it fractures like ice on a pond, and doesn't join back together, it is most likely associated with iron bacteria. If it clings to your stick and joins back together, it could be oil.

Fore more information, or to report a pollution incident, contact Council's Environmental Health Officers on (02) 4429 3453.