1st
Week →
We can observe the first changes in the column, which is divided in
two regions. In the upper one ( contains oxygen ) some algaes and
cyanobacterias. Both ones are photoautotrophs oxygenic organisms so
they only can grow in this region.
In
the lower part we can see a huge amount of black precipitate. As a
result of cellulose degradation, Clostridium
generates throughout glucose fermentation ( anaerobic process ) somo
organic compounds than can be use by sulphide-reducing bacterias such
as Desulfovibrio.
The product of anaerobic respiration (that uses sulphate as electron
acceptor ), H2S
reacts with iron contained in the mud producing FeS ( black
precipitate ).
We
can also notice some red/orange microorganisms. They are purple
non-sulphide bacterias ( Rhodomicrobium
) which are anaerobic photoheterotrophs organisms that present low
H2S
tolerance so they appear on the higher level of anaerobic region
because there is less sulphide concentration.
 |
| WEEK 1 |
2nd
Week →
The column doesn't undergo big changes. We can see a bigger amount of
FeS consequence of anaerobic microorganisms activity and some algae
have appeared in the surface of the column .
 |
| WEEK 2 |
3rd
/ 4th Weeks
→
As expected, the number of microorganisms has increased as well we
can see three main changes. In the water of the top region we can
notice some oxygen bubbles due to aerobic photoautotrophs organisms
as algae.
In
the anaerobic region, under Rhodomicrobium,
we can see white spots consisting of S (elementary sulfur) .These
spots present some purple sulphide bacterias named Chromatium
( anaerobic
photosynthetic bacterias ) that use H2S
as electron donor instead of water.
The
cloud water of the top is due to chemotrophs sulfur-oxidising
bacterias activity such as
Thiobacillus
.
 |
| WEEK 4 |
Nice column!
ReplyDeleteGiven that you have green microalgae growing on the sediment surface producing oxygen, I doubt that any H2S escapes to the water column. The turbidity observed there is thus not sulphide oxidising bacteria.