Environmental Engineering Reference
In-Depth Information
Table 1. Total number of bacteria (N, 10 6 cells ml 1 ), their average volume (V, µm 3 ), biomass
(B, mgC m 3 ), and production (mgC m 3 d 1 ) in the open Black Sea. UML is Upper Mixed
Layer (0-25 m), CIL is Cold Intermediate Layer (40-100 m), and RZ is a redox-zone (120-200
m) (modified from [53]).
Zone
N, range
V
B, range (average)
P, range (average)
Western Black Sea
UML
0.90 - 1.63
0.16
12 - 40 (22)
4.0 - 12.8 (7.4)
CIL
0.24 - 0.43
0.10
5 - 11 (8)
0.6 - 1.8 (1.4)
RZ
0.35 - 0.51
0.21
14 - 19 (16)
2.0 - 3.2 (2.6)
Eastern Black Sea
UML
0.85 - 1.05
0.15
12 - 24 (21)
4.0 - 4.9 (4.2)
CIL
0.25 - 0.34
0.08
6 - 11 (8)
1.2 - 1.4 (1.3)
RZ
0.40 - 0.48
0.25
12 - 19 (16)
2.8 - 4.6 (3.9)
3. DISTRIBUTION AND BIOMASS OF
BACTERIOPLANKTON
First measurements of bacterial numbers and biomass in the Black Sea water
column were obtained using a direct microscopic counting on membrane filters
stained with erythrosine [19]. More exact epifluorescent methods using dyes
such as fluorescamine, acridine orange and DAPI are currently in use [4, 21,
26, 39, 53]. The total number of bacteria, their biomass and productivity in the
open sea are summarized in Table 1. The upper mixed layer is characterized by
maximums of bacterial biomass and productivity. Bacterioplankton numbers
in the Cold Intermediate Layer (CIL) located at depths between 40 and 100 m
below a seasonal thermocline are usually low. This may be explained by the
transient origin of CIL, which is formed either by downwelling of the upper
mixed layer waters during winter convection in the central Black Sea or(and) by
downwelling of the NW Black Sea shelf surface waters that spread along the sea
area. Microbial density and biomass increase below the CIL and reach higher
values in the redox zone (120-200 m). The mean volume of microorganisms
that inhabit the oxic/anoxic interface increases also (Table 1). Bacterioplankton
in the oxic zone is represented by small coccoid cells of 0.4-0.6 µm in diameter
with some yeast-like and filamentous forms. Observed morphological types of
bacteria in the oxic zone of the Black Sea are typical forms of aerobic marine
heterotrophs [4, 53]. About one-third of bacteria in the oxic zone form bacterial
aggregates of 3-10µm in size. Below the thermocline and CIL these aggregates
tend to form larger particles of 'marine snow' 1-3 cm in size [52].
A typical depth distribution of the total number of microorganisms counted
using DAPI staining in the open sea is presented in Fig. 1. The vertical distrib-
ution of bacterioplankton in the water column is characterized by two maxima.
The upper one is located in the upper oxic part at the depths of 0-50 m; cell
densities are up to 10 6
ml 1 . Cell densities in the CIL are below 10 5
cel1s
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