Geoscience Reference
In-Depth Information
Concentration (μM), O
2
production (μM min
-1
)
0
200
400
600
00
1000
1200
-200
0
200
400
600
Depth
(μm)
800
1000
Oxygen Concentration
Primary Production
1200
1400
1600
1800
Figure 4.3. Oxygen distribution and rate of oxygen production for microbial mats in Baja,
California, mexico. Data from Canfield and Des marais (1993).
oxygen penetration vary from mat to mat, but as a rule, cyanobacterial
mats are extremely active.
Cyanobacteria are also not rare. They are well represented in micro-
bial mats like those we studied in Baja, and if we look hard, we might
convince ourselves that they are almost everywhere. We find them in the
beach sands of Bornholm as described in
chapter 2.
But that's just a
beginning. They form mats in the bottoms of lakes, ponds, and streams,
and are common in soils lacking higher vegetation. Thus, they are found
in particular abundance, rather paradoxically, in arid soils where water
is scarce. These cyanobacteria have the remarkable ability to survive ex-
treme drought in a dormant state, and to spring to life when water be-
comes available. Travel to the Mojave Desert and scoop up some sand.
There will almost certainly be a reasonable population of cyanobacteria
in your hand. Travel next to Uluru (formerly called Ayers Rock) in Aus-
tralia. The sands and soils surrounding this great monolith will surely
