UCA_10A_2: Day 28
Rio San Pedro sediment + Paper + 1.5g FeSO4
It’s been 2 weeks since the last
check and the column has experimented some changes that we will detail below.
First of all, we can see how the
black color that started to form in the bottom of the column has expanded all
over it, being less consistent as we go up trought the column. That indicates
the proliferation of sulphate reducing
bacteria. This type of bacteria reduces SO42- ions to
S2- ions that bind to Fe2+ in solution generating black
coloured FeS.
Our column has been stored in the
dark, so no kind of photosintetic organism has been able to grow in it. That
means no O2 production in the medium, making it almost anaerobic (still some O2
diffuses into from atmosphere), wich explains the proliferation of the sulphate
reducing bacteria (they use SO42 instead of O2
as final electron acceptor)
Besides, we notice the appearance
of some strips of orange/brown color near the surface. That indicates the
presence of some kind of iron oxidizing
bacteria that are generating Fe2O3, due to that little amount
of O2 diffusing from atmosphere. This compund provides the color
mentioned.
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| Our dark column |
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| Dark (left) vs light (right) column |
Nice. What happened to the light column?
ReplyDeleteHi, the light column turned green because of the cyanobacterias. Also we observed red regions.
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