UCA_C2_3: The conclusions of our column.

After about two months since the preparation of our Winodgrasky column, we can observe very notable changes and confirm the initial assumptions.

On the one hand, we can confirm the hypothesis of the second post on the blog about the growth of algae. Now we can see them clearly and differentiate between them at the top of the column (aerobic zone - oxygen)-. In addition, we continue watching more bubbles produced from photosynthesis in the algae as we assumed. It also must have grown cyanobacteria.

On the other hand, the column has generated a bacterial ecosystem formed by different types of bacteria which have grown up in the area more convenient for them. Thus, we can confirm the following facts:

• In the background, gray, the sulfate-reducing bacteria have grown. These bacteria have been dedicated to reduce the add sulfate to H₂S as part of their metabolic activity.
• A little above, we appreciate at areas of reddish/purple color. These are known as the purple sulfur bacteria. These bacteria are anaerobic, autotrophic organisms, that is, they make photosynthesis without oxygen (hence they grow at the bottom of column - oxygen-poor area). Instead of H2O as a source of electrons, they use H2S produced by grey bacteria, which is oxidized to S.
• At the top we can see yellowish/Orange areas. This is due to the growth of sulfur oxidizing bacteria. These bacteria, as part of their metabolism, are dedicated to oxidize sulfur (in this case produced by the purple sulfur bacteria) to sulfate.

Finally, we can also confirm the hypothesis about the gradients of oxygen and H₂S. The location of each type of bacteria and their metabolism show us that as we went down in the column the amount of oxygen diminishes, finding its maximum concentration in the surface. Otherwise, the H2S increases as go down, such that, at the bottom there is the highest concentration of H2S from the entire column.

Thus, our experiment of the Winogradsky column is completed.