Basic HTML Version
International Journal of Marine Science 2014, Vol.4, No.18: 166-178
http://ijms.sophiapublisher.com
168
USA) and flash-frozen in liquid nitrogen. Samples
were stored at -80
℃
for later analysis. Pigments were
extracted from the cells by grinding the filters each in
5mL of 90% acetone and then refrigerating in the dark
for 2 hours. Samples were then centrifuged at
4500rpm for 5 minutes, and the supernatant pipetted
into cuvettes. Absorbance was measured at 630nm,
644nm and 750nm using a spectrophotometer (U-3000,
Hitachi High Technologies, Wokingham, UK) relative
to acetone blanks to correct the readings. Chlorophyll
concentrations were finally determined using the
equations of Ritchie (2006), and normalized to cell
concentration and volume.
2.4 PIC and POC Analysis
Two aliquots of 150mL were each filtered down onto
ashed (heated in a muffle furnace at 500
℃
for 3 hours)
25mm MF300 glass fibre filters (Fisher Scientific,
Massachusetts, USA) and then placed in a desiccator
to dry for 24 hours. Samples were stored in cryotubes
to be analyzed at a later date. One of each pair of
filters was acidified with ~2M HCl to drive off
inorganic carbon, and further dried for 24 hours. The
total carbon on each filter was measured using a
carbon analyzer (Shimadzu TOC-VCSH Total Organic
Carbon Analyzer with ASV-I autosampler) calibrated
using a glucose standard. Particulate organic carbon
(POC) was measured on the acidified filters, and
particulate inorganic carbon (PIC) was calculated by
subtracting PIC from the total carbon measured on the
non-acidified filters. Both PIC and POC were then
normalized to cell concentration and volume.
2.5 Data Analysis
All parameter measured were analyzed descriptively
using Excel Program. To determine the effect of CO
2
treatments among location of mesocosms experiment,
the data was analyzed using one-way analysis of
variance (ANOVA), with an a priori contrast to test for
differences between control and treatment mesocosms.
3 Results and Discussion
3.1 The effect of increasing CO
2
to carbonate system
3.1.1 Alkalinity
Alkalinity is one of carbonate system component. It plays
a role in a maintain an equilibrium of carbonate
concentration in the water. Alkalinity at mesocosm
experiment that run at three different locations showed a
varied response within CO
2
treatments (Figure 2).
Figure 2a showed that there was trend for decreasing
alkalinity with increasing CO
2
concentration for both
incubation periods at Barru mesocosm experiment. The
lowest alkalinity was found at 96 hours incubation period,
which was account for 87.2 mg/L. However, alkalinity at
48 hours incubation period tend to be higher than 96
hours incubation periods for all CO
2
concentration
treatments.
Alkalinity at Takalar mesocosm experiment was
similar pattern with Barru, which was a trend to
decrease of alkalinity with increase of CO
2
concentration for both two periods of incubation
(Figure 2b). Howerver, there was no significance
different of alkalinity between CO
2
concentrations and
length of incubation periods.
Alkalinity was slightly different trends between
incubation periods amongs CO
2
concentration at
mesocosm experiment for Barrang Lompo Island
(Figure 2c). It showed that there was a variation of
alkalinity between incubation periods. There was
slightly difference of alkalinity amongs CO
2
concentrations for both two incubation periods.
3.1.2 Dissolved inorganic carbon (DIC)
Dissolved inorganic carbon (DIC) showed a similar
pattern among CO
2
concentrations between two
different lengths of incubation for Barru and Barrang
Lompo mesocosms experiment (Figure 3a and 3c).
Statistically, there was no significant difference of
DIC between CO
2
concentrations for both periods of
incubation. For Barru mesocosm experiment, DIC was
slightly lower at 1000 ppm CO
2
concentration than
others CO
2
treatments for both incubation periods.
CO
2
concentration of 750 ppm showed a lower DIC
than other CO
2
treatments for two periods of
incubation at Barrang Lompo mesocosm experiment.
Interestingly, there was a different pattern of DIC
between CO
2
treatments and length of incubations for
Takalar mesocosm experiment (Figure 3b). DIC
tended to be lower at 46 hours of incubation period
than 96 hours incubation period for all CO
2
treatments.
The different DIC between locations of mesocosm
experiment were due to different of other carbonate
chemistry variables, such as pH, pCO
2
, and HCO
3
-
.
Increasing CO
2
concentration also could change
carbonate chemistry at the water column. Adding CO
2
to seawater increases aqueous CO2, bicarbonate, and