Figure 3 : Ribulose biphosphate carboxylase
(RUBPC ase) activity vs. CO2 dark fixation in
vivo at different sampling sites in bioturbated
sediment of Stein Lagoon.
In vertical profiles from other coastal sediments, CO2 dark fixation peaked within the
redox potential discontinuity (RPD) layers. These were located 2-3 cm below the surface,
when the sediments were oxidized and bioturbated, but bound to the sediment surface,
when anoxia had reached the uppermost cm and a burrowing macrofauna was absent
(Fig. 4). Although no simple correlation existed between CO2 dark fixation and Eh, the
rates usually tended to decline rapidly below 100 mV, which is also evident from this
example.
Figure 4 : CO2 dark fixation in vertical profiles
of sediments with and without bioturbation.
• = Kiel Bay at Boknis Eck, 18 m (bioturbated),
O = Kiel Bay at Boknis Eck, 28 m (without burrowing infauna), A = Limfjorden at Bjornholm
Bugt, 1 .0 m (bioturbated). Eh values are shown for
the depths with maximal and minimal CO2 fixation rates obtained with core injection technique
at in.situ temperatures in April (O) and August (•,
A).
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