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International Journal of Marine Science 2014, Vol.4, No.18: 166-178
http://ijms.sophiapublisher.com
167
planktonic and benthic habitats (Bijma et al., 1999;
Delille et al., 2005).
Ocean acidification impact to marine organisms have
been well investigated at marine temperate and
subtropic ecosystem at the monoculture species of
laboratory experimental condition. Langer et al (2006)
found that foraminifera, coccolithophores and corals
each showed a decrease in calcification with
increasing CO
2
concentration.
Cellular calcification
could be depressed consequently to a rise of pCO
2
in
seawater. For example, by increasing pCO
2
in
phytoplankton culture by the mean of strong acid
addition, a significant decrase of the calcification rate
and of the calcification photosynthesis ratio was
induced in
Gephyrocapsa oceanica
(Riebelsell et al,
2000; Rost and Riebelsell, 2002). Gattuso et al (1998)
found that Calcification rate increase exponentially as
a function of increasing aragonite saturation state
above the 100% saturation level and reaches a plateau
at saturation values greater than 300%. They also
explained that calcification changes as a function of
calcium concentration in several taxonomic groups.
For example, the rates of calcification and
photosynthesic
14
CO
2
fixation increase as a function of
external Ca
2+
concentration in cells harvested from the
exponential growth phase of a high-calcifying strain of
the coccolithophoreid
Emiliana huxleyi
(Xu et al.,
2011). The rate of photosynthesis and calcification are
closely coupled, ad are saturated at 10 mM Ca
2+
compared with the Ca
2+
concentrationof 8 mM in
seawater. Lea et al. (1995) found that the calcification
rate of the foraminifera
Orbulina universa
is
proportional to the degree of carbonate saturation.
However this process has investigated poorly at
natural phytoplankton community of tropical
ecosystem through the mesocosm study. On the other
hands, there is very important ecosystem that
contribute to decrease CO
2
concentration through
photosyntetic which is coral reef ecosystem. It is
important to understand ocean acidification process
and their impact to marine organisms especially in the
tropical systems. The aim of this research examined
deeply natural phytoplankton community response to
increase CO
2
concentration which is part of ocean
acidification process.
2 Methods
2.1 Mesocosms experiment
Mesocosms experiment have been conducted at three
different locations (Barru, Takalar Regency and
Barrang Lompo Island) on June – August 2013 to
examine the impact of ocean ocidification upon
marine organisms in focus on phytoplankton at
tropical system. The treatments in this experiment
were six pCO
2
level through manipulating culture
media through adding acid-base solution for to get
expected CO
2
concentrations. Six treatments of pCO
2
level were 280, 380, 550, 650, 750 and 1000 ppm with
4 replicates for each treatment. There was two kinds of
incubation periods such as 48 hours and 96 hours.
24-2L water bottles were incubated at 1 m depth
below the surface and randomly placed (Figure 1).
Figure 1 Incubated water bottles at 1 m depth below the surface
during mesocosam experiment.
2.2 Growth rates
Cells were counted daily by taking a 2mL sample from
each culture and measured microscopically using a
Neubauer haemocytometer slide (Fisher Scientific,
Loughborough, UK). Growth rates (μ) were calculated
using the following equation:
where c
0
is the initial count (cells mL
-1
), c
1
is the final
count (cells mL
-1
), and Δt is the time between the two
counts (days).
2.3 Chlorophyll a Analysis
A volume of 2L was filtered through 25mm MF300
glass fibre filters (Fisher Scientific, Massachusetts,