ID
Major Adfdrfg Title of Acidification
MN Islaaa*, BE Ccccc, and Y Sdddd
Graduate School of Science and Technology, Uuuu University, Japan
*e-mail: mn_mmmm@uuuu.edu
Abstract
To test the effects of (4 days under dark condition) were carried out using white coral skeleton (no attachment of living
organism), natural rubble (… the control. In the short incubation experiment, addition of bioavailable organic matter further
increased carbonate dissolution by enhancing bacterial activity under ambient and high pCO2 condition. These suggest that
biological processes play a significant role in determining calcification and dissolution.
INTRODUCTION
The acidification of the oceans is the ongoing
decrease in pH of the oceans, caused by the uptake of
anthropogenic CO2 from the atmosphere [1]. Since
the beginning of the industrial revolution, about
30–40% of the carbon dioxide approximately 79
million tons per day released in the atmosphere by
human activities has been absorbed by the oceans
[2-4]. The concentration of carbon dioxide (CO2) in
the atmosphere is 396 ppm [5] and increased 2.1 ppm
per year during past decade (2003-2012). However,
increase in atmospheric CO2 has decreased the
world’s ocean pH about 0.001 to 0.002 pH units per
year over the past several decades [6].
niferans [13] and also photosynthetic plankton
coccolithophorids [14-16] that have shells or plates
of calcium carbonate (CaCO3) and leads to
dissolution of CaCO3 sediments in reef flats [15].
The acidification of the oceans could affect the
dissolution of carbonate skeleton of calcifying
organisms as well as coral rubble [17]. Dissolution of
carbonate based on the solubility (Ω) of calcite or
investigate the importance of biological processes
(especially respiration) to the dissolution of calcium
carbonate by examining the response of coral rubble
and its associated microbial communities with
addition of organic matter under elevated pCO2.
MATERIALS AND METHODS
A. Study area and collection of samples
The study area is located in a shallow fringing
coral reef at Sesoko Island, Okinawa, Japan between
26°38′ N and 127°51′ E (Fig. 1). Coral rubble coral
mucus was collected from Acropora digitifera
species using air exposure method [18]. Seawater
was collected by using Nalgene bottle and filtered by
0.2 μm isopore membrane cartridge filter before
incubation.
Fig. 1. Map showing the study area and the location of
sample collection (○) at Sesoko Island, Okinawa, Japan
(Source: using Google map)
B. Preparation of incubation experiment
Incubation experiments were carried out in natural
illumination (24h short) and dark (4 day’s long)
under different level of pCO2 (Ambient, 520, 720 and
1120 (1L) to make final concentration of 10µM. In
case of coral mucus, 10% mucus solution was added
to the incubation bottles. Temperature and light
intensity were monitored during the experiments
using in situ sensors (MDS-MkV/T and
MDS-MkV/L, Alec electronics).
C. Measurement and analysis
Measurement of short incubation (natural
illumination) experiment was done 24 times per day
(1h interval) and 4 times per day (6h interval) for
long (Nikon; ECLIPSE/E600), using a UV-filter.
Carbonate dissolution rates were analyzed using the
alkalinity anomaly technique [19] and saturation state
of aragonite (Ωarg) were calculated with the program
CO2SYS [20].
RESULTS
A. Introducing third sector organizations
Natural rubble (NR) are colonized by epilithic and
endolithic algal communities and by other
heterotrophic organisms as bacteria, foraminifera,
nematodes, copepods, etc (Fig. 2, 3, 4).
During 4 day’s long incubation experiment under
dark condition; the bacterial abundance, net d white
skeleton to natural rubble, it is possible to assess that
80% of dissolution was due to the contribution of
biological processes (Table 1).
Ambient
520 ppm
720 ppm
1
4
1
1
1
4
1
1
5
4
1
1
2
4
1
1
4785
WCSk: White coral skeleton; NR: Natural rubbles with associated
epilithic and endolithic communities; Bac. Abundance: Bacterial
abundance; Net Res.: Net respiration [ΔCO2 = CO2 final – CO2
initial]; Dis. Rate: Dissolution rate; Sat. State: Saturation state;
Mean ± SD
Fig. 2. Photograph of natural coral rubble (left) and a
transverse section of it (right) showing the endolithic (green
band) and epilithic algae [17]
B. Addition of bioavailable organic matter
Bioavailable organic matter (glucose and coral
mucus), was added to the incubation bottles to
enhance bacterial growth and their physiological
3bottles, bacterial abundance and dissolution rates
increased 5~6 times more than the control (NR)
(Table 2).
Table 2. Summary result of 24h natural illumination short
incubation experiment
Bac.
Abundance
5
-1
Net
Res.
Dis.
Rate
-2 -1
Sat.
State
-2 -1
[Cells×10 ml ] [mgCm d ] [mmol m d ] [Ωarg]
Ambient condition
NR
4
High pCO2 (1120 ppm) condition
NR
4
NR+G
5
5
5
Fig. 3. Photographs of epilithic microbial communities (a)
coccoid green algae; (b) green algae; (c) red calcareous
algae; (d) algal colony; (e, f) diatoms; (g) nematode; (h, i)
foraminifers; (j) cyanobacteria [17].
4
4
4
5
5
5
2
5
5
85
5
5
NR: Natural rubbles with associated epilithic and endolithic
communities; NR+G: Natural rubbles with addition of organic
matter (Glucose); NR+M: Natural rubbles with addition of organic
matter (10% Coral mucus); Bac. Abundance: Bacterial abundance;
Net Res.: Net respiration; Dis. Rate: Dissolution rate; Sat. state:
Saturation state; Mean ± SD
C. Carbonate dissolution vs. saturation state
Calcium carbonate dissolution rates increased
and saturation states (Ωarg) decreased with 33olution
rate and saturation state (r=–0.99; p=0.0002)(Fig.
5).
Fig. 4. Heterotrophic bacterial communities in coral rubble
Table 1. Summary result of 4 day’s long incubation
experiment under dark condition
Bac.
Abundance
Net Res.
Dis. Rate
Sat.
[∆CO2 ppm] [mmol m-2d-1] State
[Cells×10 ml ]
[Ωarg]
3
-1
Fig. 5. Relationship between aragonite saturation state
(Ωarg) and carbonate dissolution rates
WCSk
Ambient
4
4
4
NR
1.12108 ±
0.014
4
4
4
22
4
4
4
22
4
4
4
22
DISCUSSIONS
4
4
4
Dissolution of calcium carbonate of calcifying
organisms and their skeletons occurs due to reduction
respiration intensified carbonate dissolution.
Moreover, when the abundance of bacteria was
enhanced with addition of bioavailable organic
matter (glucose and coral mucus), the rate of
dissolution was further increased (Table 2). Bacterial
processes play an important role as demonstrated in
the “Bio-Chemical Dissolution Processes (BCDP)”
[17] (Fig. 6).
Carbonate dissolution occurs when saturation state
with respect to carbonate minerals is less than one [9,
10r experiment, dissolution occurred when the
saturation state (Ωarg) ranged from 2.87 to 0.88 in
coral rubble.
[7]
[8]
[9]
[10]
[11]
[12]
[13]
[14]
Fig. 6. n and solid arrow indicates major contribution for
dissolution [17]
CONCLUSION
Ocean acidification plays fundamental changes in
enhancing heterotrophic bacterial communities and
their biological activities.
ACKNOWLEDGMENT
We would like to thank to Environmental Leader)
of o Island, Okinawa, Japan for providing laboratory
facilities.
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