Second post: The evolution of our Winogradsky column. Group A4.

In this post we will discuss the progress of our column during the last four weeks.

First week:
Four parts are distinguished:
At the bottom of the tube we can see bubbles which expands to the Surface . It seems like a volcano.
Due to the presence of an acumulation of organic material, the microorganisms make methanogenesis, althought this is one of the less efficient source of energy. This process produce the grey colour .
Above the grey colour, we can observe a black area where oxigen can´t access ,so the microorganisms who live there are anaerobic and instead of using this molecule they take the sulfate and release  sulfuric acid and carbon dioxide. The sulfuric acid reacts with iron producing iron sulfate, which is a black precipitate.
In the third zone, the orange and black colours are mixed . This part can be reached by oxigen , so microorganisms are aerobic and organoheterothophs. The orange colour is a consequence of the photosinthetic pigments.
In the last part, at the top of the column, there is some orange water without any algae but in the surface there is an oily liquid due to the bacteria.

                      
Second week:
This time, we can distinguish three parts:
The bottom of the tube has stayed grey, due to the methanogenesis, as the last week.
The orange liquid of the surface has not change neither.
The principal changes have occured in the black zone of the tube (at the middle). It has expanded, because of the acumulation of organic material.
At the surface of the  mud, a green colour has appeared which indicates presence of photosinthetic microalgae.
                                         
Third week:
The black zone of the bottom of the tube has not changed. However, in the middle of the tube a light pink colour has appeared, due to the presence of a special photosintetic bacteria. It assimilates sulphur and produce sulfate instead of oxigen.
At the surface, the orange colour is mixed with green and brown. As we said, the green colour has appeared because of the growth of photosinthetic microalgae.

                   

Fourth week:
The major change is that the pink colour has become more intense and dark, because the bacteria has increased the concentration of sulfate.
At the same time, it has appeared bubbles at the surface because of the presence of oxigen produced by photosinthetic microalgae and cianobacteria.
The gas produced in the methanogenesis has created some breaks which we eliminated by hitting the table with the column.
The column was warm due to the biological activity and the solar heat.
In general, we have noticed a disgusting smell every week because of the excess of sulphur.