Environmental Engineering Reference
In-Depth Information
Figure 2.
Vertical profiles of prokaryotic abundances and activity obtained on 16 Jan 02 at
Station CARIACO (CAR-74). (a) solid circles and error bars = mean
+
SE of total prokaryotes
(hetero- and autotrophic Bacteria and Archaea); shaded area defines dissolved O
2
profile deter-
2
determined in discrete
samples by Winkler titration; squares = H
2
S concentrations determined in discrete samples (see
[44] for chemistry protocols). (b) open diamonds = mean
+
1 SD of dark DIC assimilation in
triplicate samples; broken lines = % of surface irradiance determined at three wavelengths by
spectral radiometer, wavelengths are listed in order of extinction (532 nm deepest). (c) solid
diamonds and error bars = mean
+
1 SD of bacterial net production in triplicate samples; shaded
circles = specific rates of
14
C-acetate turnover determined in time course experiments (see [14]).
mined by polarographic electrode on rosette: triangles =
dissolved O
this are relatively homogenous with σ
θ
only increasing by 0.060 kg m
−
3
from
200 to 450 m and by 0.024 kg m
−
3
between 450 m and the seafloor (Fig. 3a).
Therefore, accumulation of prokaryotic cells along density surfaces between
250 and 450 m based on buoyancy is highly improbable. Warm deepwater
temperature (
>
17.2
◦
C at 1380 m) is another unique feature of the Basin which
contributes to its weak stratification and undoubtedly accelerates chemical and
biological reactions.
Fluorescence profiles confirm that phytoplankton standing stocks are largely
confined to the upper 50-100 m of the Cariaco and rapidly diminish with depth
(Fig. 3b). Vertical profiles of light scattering (beam attenuation coefficient)
suggest that bulk particle distributions are far less uniform than live phyto-
