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International Journal of Marine Science 2014, Vol.4, No.18: 166-178
http://ijms.sophiapublisher.com
173
3.2 The effect of increasing CO
2
to chl a, cell
abundance, growth rate and photosynthesis rate
3.2.1 Chlorophyll a concentration
Chlorophyll a concentration showed a varies trends
between CO
2
concentration treatment for each
location during two periods of incubation (Figure 7).
Figure 7 showed that Chl a concentration for 96 hours
incubation periods of mesocosm experiment at Barru
was higher than 48 hours of incubation period at all
CO
2
concentration treatments (Figure 7a). However,
there was a similar trends of chl a concentration
between 48 and 96 hours of incubation periods among
CO
2
concentration treatments. Chl a concentration
tend to decrease with increasing of CO
2
concentration.
The lowest Chl a was found at 1000 ppm of CO
2
concentration for both 48 and 96 hours of incubation
period. This result showed that there was a significant
effect of increasing CO
2
concentration in
phytoplankton Chl a concentration production.
Chlorophyll a concentration tends to be lower at 48
hours than 96 hours incubation period with increasing
of CO
2
concentration, except at 280 and 550 ppm CO
2
for mesocosm experiment at Takalar (Figure 7b). The
lowest Chl a concentration was found at 1000 ppm
CO
2
for 48 hours incubation period account for 0.1782
mg/L and the highest Chl a concentration was 2.678
mg/L at 280 ppm CO
2
treatment in 48 hours
incubation period.
Interestingly, the pattern of Chl a concentration for
mesocosm experiment at Barrang Lompo Island was
slightly different from the other locations of
mesocosm experiment (Figure 7c). Figure 4 showed
that Chl a conentration at all CO
2
treatments were
higher at 48 hours than 96 hours of incubation period.
However, the trend of Chl a concentration was similar
between 48 hours and 98 hours of incubation period,
which was decreasing of Chl a concentration with
increasing of CO
2
conentration.
3.2.2 Cell abundance
Cell abundance was varied between CO
2
concentrations and length of incubation periods for all
mesocosms experiment (Figure 8). For Barru
mesocosm experiment, increasing CO
2
concentration
affected significantly in decreasing cell abundance for
both incubation periods (Figure 8a) and cell
abundance was higher at 96 hours than 46 hours
incubation period for all CO
2
treatments. Cell
abundance at Takalar and Barrang Lompo mesocosm
experiment showed a similar trend with increasing
CO
2
concentration for both incubation periods (Figure
8b and 8c), which were a slightly different in cell
abundance between 48 and 96 hours incubation period
for all CO
2
treatments. The highest number of cell was
found at Barrang Lompo mesocosm experiment
account for 3250 cell and the lowest number of cell
was found at Barru mesocosm experiment which was
accounted for 100 cells.
3.2.3 Growth rate of phytoplankton
Results showed increasing CO
2
concentration affected
negatively on growth rate of phytoplankton. All
locations of mesocosms experiment showed a negative
growth rate of phytoplankton with increasing CO
2
concentration for both incubation periods (Figure 9).
However, the longer incubation period was the lower
negative value of phytoplankton growth for all CO
2
treatments. The highest negative value of growth rate
was found at Barru mesocoms experiment on 1000
ppm CO
2
concentration for 48 hours incubation
periods (Figure 9a). On the other hand, the positive
value of growth rate was found at the same location of
experiment on 280 ppm CO
2
concentration for 96
hours incubation periods. This result was consistent
with previous research, which showed that specific
growth rate of
E. huxleyi
, which de- creased with
pCO
2
and might have influenced differences in net
PIC accumulation. Because net specific growth rates
were derived from changes in cell concentration, we
have to speculate whether cell division rate was
directly affected by the CO
2
treatment or whether
different loss rates (i.e., by grazing, sinking, or
autolysis) occurred (Engel et al., 2005).
3.2.4 Photosynthesis rate
Photosynthesis rate is strong correlated to growth rate
and POC production of phytoplankton. This study
found that photosynthesis rate for all mesocosm
experiments was negative due to the growth rate of
those experiment were negative. However,
photosynthesis rate was varied between CO
2
treatments and length of incubation period for all
mesocosm experiments (Figure 10).
Figure 10 showed that increasing CO
2
concentration
affected on decreasing photosynthesis rate at all location