Occasionally we notice some curious (natural) goings-on in the park and we do our best to figure out what’s happening. Recently a Friend pointed out an area with rust-coloured water running over the lakeside paths – what was it? where did it come from? Was there a giant iron structure buried in the park??
Luckily for us, Gary (one of the gardening volunteers) and his partner Lucy have some expertise in related areas, and Gary emailed to say:
We think that what you’re seeing in the park is the result of iron bacteria, so-called because they use iron, rather than oxygen, during their respiration. In their life cycles, soluble iron from the soil gets turned into insoluble iron (‘rust’, which appears as orange/red slime). This whole process could be a byproduct of all the organic compounds being provided by the multitude of geese and ducks in the park, which will of course encourage growth of microorganisms, which will then use up all the oxygen, allowing anaerobic bacteria in turn to then take control of the ecosystem.
We then asked a follow-up question, about the oily sheen that is sometimes seen in the same areas, and we got this answer:
In this case the oily sheen is the result of the iron bacteria, but rather than hydrocarbons being produced by the bacteria, it could be the bacteria themselves; they’ll proliferate madly but as things become tough they’ll start to die and break down, resulting in an oily sheen. That, or the products they make take on the resemblance of being hydrocarbons or oil, but actually aren’t.
So it looks like Rowntree Park is neither the burial place of a prehistoric iron-working site (a great disappointment to some people!) nor the potential location of Yorkshire’s biggest oil field (a great relief to us all!) But it is fascinating what can emerge if you ‘Ask a Scientist.’
Thank you, Gary and Lucy!