UCA_6B_2: Day 14 - The Return of The Column

Rio San Pedro sediment + 1g CaSO4


Our column has return from the dark side (the box) and we can see some changes. The whole column has little dark stains between the sediment and we could recognize them as reduced Iron.

The bottle with the FeS (black stains)

This is a result of two situations: the first one is the change of the pH (which is more acid) and the other and more important one is that some microorganisms obtains energy oxidizing the Iron like, for example the Thiobacillus ferroxidans, so the dark stains we can see are the FeS created by the microorganisms that reduce the Iron.

The water is dimer due to the increase of the organic matter (due to the eutrophication). Compared to the others columns ours is darker because of the high proliferation of the microorganisms, who will reduce the Iron. The high proliferation is helped by the CaSO4 which is use by the chemosyntethic microorganisms as nutrients in the trophic chain.

We add some photos to see what we describe in the post: 

The top of the column.