Environmental Engineering Reference
In-Depth Information
Figure 5.
Representative depth profile of
35
S-sulphate reduction rates and cumulative percent-
age of sulphate reduction, here shown for M57-3 Station 178, March 2003.
oxidation of hydrogen sulphide to dissolved oxygen and nitrate. Since oxygen
concentrations are already very low near the sediment-water interface, the
major amount of hydrogen sulphide oxidation must take place by the reduction
with nitrate. Studies of the large sulphur bacteria
Thioploca
,
Beggiatoa
, and
Thiomargarita
over the past 10 years have indicated their capacity for using
nitrate as an alternative electron acceptor [24, 29]. Adaptations such as the
intracellular storage of nitrate and elemental sulphur in vacuoles enable the
bacteria to survive periods when electron donor and acceptor are limited in
the ambient environment. The intracellular storage of nitrate may allow the
bacteria to survive for up to 8 months [33]. Although the actual survival period
of the bacteria in nature is uncertain, the principal conclusion is that sulphide
oxidation can be decoupled from the contemporaneous presence of nitrate or
