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| Iron floc seeping from the stream bank |
Floc is the fluffy material you see in some waterways, sometimes forming
soft stalks. It is quite delicate and will break apart easily when disturbed so
even though it may not be ‘aesthetically pleasing to the eye’ it is an
important metabolic process that should be allowed to occur, and in fact is
likely to be a very ancient process in the context of the development of life
on earth (there is actually a good deal of research on different iron oxidizing
bacteria, and it is a worldwide phenomenon). The harvested electrons by the bacteria provide
energy for reproduction and other life-sustaining processes in the life of
these single-celled organisms. A variety of species and sub-species of bacteria
carry out this process. It requires oxygen, so these bacteria live and
reproduce where iron-rich water flows out of the ground and is exposed to
oxygen in the air. This is a completely natural process.
Interestingly enough, and it has not been worked out why, we
find that giant kokopu are very fond of streams that have lots of iron floc,
with good populations in some urban and perimeter urban Hamilton streams.
In this You Tube clip https://youtu.be/8w0kgAwv1Ps taken in the Gordonton arm (zone 3) of Mangaiti Gully stream
you will see the iron floc floating about from the disturbance of the eels. A
giant kokopu is visible at the end of the clip. Kōura / freshwater crayfish
have been found a little downstream from this photo point. All indicating
healthy stream fauna happily living among the iron floc.
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