VOLUM OMAGIAL - Facultatea de Ştiinţe ale Naturii şi Ştiinţe Agricole

Changes in bacterial abundance and biomass... / Ovidius University Annals, Biology-Ecology Series 14: 139-145 (2010)
Biomass (µg)
3.5
3
2.5
2
1.5
1
0 14 28 42 56
Time (days)
Fig. 2. Bacterial dry biomass (µg/cm 3 ).
Bacterial biomass
Biomass showed large variations, from 1.36 to
3.13 µg/cm 3 sediment (equivalent to 4.3 to 11.4 µg
total biomass/cm 3 ). On average, the highest biomass
was determined for the undisturbed sediment (an
average of 2.27 µg/cm 3 ). The addition of gasoline was
followed by a decrease in microcosms B and C. The
average value for contaminated sediment in
microcosm B was only 1.7 µg/cm 3 , while in C, it was
higher (2.12 µg/cm 3 ), showing a faster recovery.
The importance of nitrogenous nutrients in the
recovery of natural microbiota after hydrocarbon
pollution is consistent with data in existing literature
[33, 34].
The exact determination of bacterial biomass can
be affected by various technical and mathematical
factors. Different fluorochromes can give different
results [16]. The selected biovolume to biomass
conversion factor influences the final results. Also, it
was demonstrated that coastal marine sediments
contain significant numbers of disk-shaped bacteria
and counting them as cocci would overestimate their
volume [35].
Proportion of major bacterial morphotypes.
As specified above, bacteria were classified into three
groups: cocci, rods and filamentous. Their proportion
in the total abundance, for each microcosm and
collection time is shown in Fig. 3 (a,b,c).
A
B
C
142
100%
80%
60%
40%
20%
0%
100%
80%
60%
40%
20%
0%
100%
80%
60%
40%
20%
0%
Microcosm A
0 14 28 42 56
Time (days)
Microcosm B
0 14 28 42 56
Time (days)
Microcosm C
0 14 28 42 56
Time (days)
Filamentous
Rods
Cocci
Filamentous
Rods
Cocci
Filamentous
Rods
Cocci
Fig.3 (a,b,c). Percentage of major bacterial
morphotypes