Ocean Acidification: Cause, Impact and mitigation

Ocean Acidification and the battle for
carbonate
Presented by-
 Shubham Gupta
 Sajal Mittal
 Kumar Saurav
 Kunal Ghosh
 Gyanesh K. Singh

What is ocean acidification…?
“A reduction in ocean pH due to the uptake of anthropogenic CO2.”
(Hofmann et al 2010)
• Ocean Acidification is a term used to describe the change in chemistry of the Earth’s
Ocean i.e. ongoing decrease in pH and increase in acidity, caused by the anthropogenic CO2
uptake
26%
29%
45%
Fate of Anthropogenic CO2 Emissions
Source: Le Quéré et al 2013
Sources Sinks

Mauna Loa , Hawaii (13,677 ft = 4169 m)
Key concepts:
1. Atmospheric CO2 is increasing

Key concepts:
1. Atmospheric CO2 is increasing
Mauna Loa , Hawaii (13,677 ft = 4169 m)
Currently 30% higher
than since last 650,000
years
(Feely et al 2009)

Key concepts:
2. CO2 sink in the Oceans

Key concepts:
2. CO2 sink in the Oceans
• Water naturally absorbs CO2 from the air
• The more atmospheric CO2, the more the ocean absorbs

Key concepts:
3. Water becomes more acidic the more CO2 it contains.

Key concepts:
CO2 reacts with H20 to produce:
bicarbonate ion (HCO-
3)
hydrogen ion (H+)

Key concepts:
CO2 reacts with H20 to produce:
bicarbonate ion (HCO-
3)
hydrogen ion (H+)
this H+ ion is making ocean more acidic

Key concepts:
4. Increased ocean acidity affects marine organisms’ abilities to make and keep their
hard parts (calcium carbonate (CaCO3) shells, skeletons, etc.)

Key concepts:
Many marine organisms have CaCO3 hard parts
• Carbonate ion is used for the formation of the hard part(shell, skeleton, etc.)
which they get from the sea-water
BUT, hydrogen also naturally reacts with CO32-

Key concepts:
• The more acidic the ocean, the more CO32- reacts with hydrogen, and the
LESS CO3 left for marine organisms to convert into their hard parts
“Battle” for carbonate!

Key concepts:
• The more acidic the ocean, the more CO32- reacts with hydrogen, and the
LESS CO32- left for marine organisms to convert into their hard parts
“Battle” for carbonate!
• Organisms must use more energy or make
less hard part material
•Existing hard parts dissolve (chemical
reaction goes “the wrong way”)

Chemistry of Ocean Acidification
• Relative proportion of these species vary with pH; increase of CO₂
invasion into seawater leads to increased concentration of CO₂(aq.) and
HCO₃¯ and a decreased concentration of CO₃²¯ (91% of DIC exists as
HCO₃¯ 8% as CO₃²¯ and 1 % as CO₂)

Change in the concentration of DIC
Dissolve Inorganic Carbon (DIC)
Bicarbonate ion (91%)
Carbonate ion (8%)
CO2 (1%)
pH 8.2 : Pre Industrial Value
pH 8.1 : Present Value
pH 7.4 : When all fossil fuel burnt
(Tyrrell et. Al. 2011)
CO3
2- (8%)
HCO3
- (91%)
CO2 (1%)

Indicators
• Shows pH values and levels
of dissolved carbon dioxide at
three locations
• Data come from two
stations in the Atlantic Ocean
(Bermuda1 and the Canary
Islands2) and one in the
Pacific (Hawaii3)
• Measured directly or
calculated from related
measurements such as
dissolved inorganic carbon
and alkalinity.
Source: Bates et al., 20121 , González-
Dávila, 20122, University of
Hawaii, 20123

Indicators
Source: Feely et al., 2009
Related Information at http://sos.noaa.gov/Datasets
/list.php?category=Ocean
• Amount of aragonite
dissolved in ocean water, which
is called aragonite saturation
• Aragonite saturation
measurements done only at
selected locations
• But it can be calculated
reliably for different times and
locations based on the
relationships scientists have
observed among aragonite
saturation, pH, dissolved
carbon, water temperature,
concentrations of carbon
dioxide in the atmosphere, and
other factors that can be
measured
•So this is indirectly based on
actual measurements

Feely, Doney and Cooley,
Oceanography (2009)
pH distribution in surface waters
pH
from the NCAR CCSM3 model projections using the
IPCC A2 CO2 Emission Scenarios
Projections

Ocean Acidification in the Past
• 55 million yr ago Earth went to the
same change, this ancient catastrophe
is known as Paleocene-Eocene thermal
maximum, or PETM
• 5X CO2 in the atmosphere
• 0.8 pH unit lower
• Temp was 60C to 100C high
• So corrosive that it ate away at the
shells, along with other species with
calcium carbonate in their bodies
• It took hundred of thousand of years
to recover from this crisis and seafloor
from red black to white
How is present OA differ from
PETM…?
• Acidification rates is 10X
• Anthropogenic CO2 blast

IPCC Projections for 2100
• Anthropogenic Ocean acidification is currently in progress and its measurable
• Reducing CO2 emission will slow the process of ocean acidification
Global temperature
increase likely by
2100:
0.9°C – 2.3°C
3.2°C – 5.4°C
0.3-0.4 pH unit
drop expected

Revelle factor is defined as
• Describes how partial pressure of CO2 in seawater changes for a given
change in DIC
)/()(
/ 22
DICDIC
PP COCO
• Proportional to ratio btwn DIC and alkalinity (oceanic charge balance).
• Low Revelle factors generally in
warm tropical and subtropical
waters
• High Revelle factors in cold high
latitude waters

Capacity for ocean waters to take up anthropogenic CO2 is
inversely related to the Revelle factor
• Highest anthropogenic CO2
concentrations found in
subtropical Atlantic due to
low Revelle factor
• North Pacific has high
Revelle factor  lower
anthropogenic CO2
concentrations

Main Causal factors affecting Ocean Acidification
 Rivers
 Anthropogenic
 Volcanic Vents
 Ships

SATURATION INDEX
OF ARAGONITE (Ω)
Ω = [Ca2+] [CO3
2-] /Ksp
Saturation Index
of aragonite, or
degree of
saturation relative
to aragonite
stoichiometric
solubility
product
Ω=1, Saturation
Ω>1, Oversaturation (required to form shell)
Ω<1, under saturation
• Aragonite is 1.5 times more soluble than calcite.
• Increase in acidity cause carbonate equilibrium towards lower CO3
2- and lowers the
saturation index of aragonite (Ω) .

EFFECT OF RIVERS
ON
SHELL GROWTH
Fig. 1. Effect of increased acidification on
soft- shelled clam larvae.
• The increase in alkalinity with time at Ω =
0.5, indicates that shell dissolution is
occurring, as the gain in alkalinity of the
solution is proportional to the decrease in
shell material.
•At Ω = 2.0, the decrease of alkalinity
indicates shell formation and growth.
•When seawater is supersaturated at Ω = 1.6,
the rate of alkalinity change (CO3
2- uptake) is
effectively zero.
The early spawn coincides with the river
discharge which unable larvae to incorporate
aragonite at Ω=1. 6.

COASTALACIDIFICATION BY
RIVERS
Fig. 2. Mapped Ω for the surface waters of
the Kennebec plume and Casco Bay, Gulf of
Maine. Contours of Ω = 1.0 (inner) and
Ω=1.6 (outer) are shown as black curves.
Source: BY J. SALISBURY (2005)
Fig.3. The Gulf of Mexico (above) has a
large dead zone due to excess nitrogen.
Source: NASA

Fig. 4.(a) Estimated Ω versus salinity of several major world rivers: 1, Mississippi; 2, Yangtze; 3,
Nile; 4, Congo; 5, Amazon; 6, Mekong; 7, Orinoco; 8, Yenisey; 9, Amur; 10, MacKenzie; 11, Ob.
Note the strong patterns in grouping by alkalinity and latitude. (b) A look at Ω as a function of
salinity for the region of the Amazon and Orinoco plumes. Black contour shows the estimated
extent of the combined plumes. Source:BY J. SALISBURY(2005)
•Climate and river chemistry are the main factors determining Ω, with low temperatures and
carbonate favouring lower Ω.
• To consider the potential threat to marine species (specially shellfish) on a global scale, we
estimated Ω from the low-salinity region near the river mouth out into the open ocean for several
of the world’s major rivers.

IMPACT OF ANTHROPOGENIC
CO2
• CO2 increase from 280ppm to 398.03ppm from the industrial period due to several human
activities.
• 45% remain in atmosphere
• 26% has been taken up by ocean
• 29% by the terrestrial biosphere
Fig.5. Atmospheric CO2
emissions, historical
atmospheric CO2 levels
and predicted CO2
concentrations from this
emissions scenario,
together with changes in
ocean pH based on
horizontally averaged
chemistry
Source: Feely.et.al(2004)

Fig.6. Relation between the
CO3
2-, pCO2 and DIC. The
solid vertical light green
line shows the range of
carbonate ion
concentrations observed in
the present-day oceans, and
the solid vertical magenta
line shows the range of
dissolved inorganic carbon
concentrations.
• Surface-water dissolved inorganic carbon (DIC) increase by more than 12%, and the carbonate
ion concentration would decrease by almost 60%.
• The corresponding pH drop would be about 0.4 pH units in surface waters.
EFFECT ON SATURATION DEPTH

• The primary production carbonate shells occur in euphotic zone.
• Initially we think dissolution occur after CCD, but 60 to 80% of the CaCO3 dissolves in the
upper 1000 m.
Fig.7. Distribution of (A)
aragonite and (B) calcite
saturation depth. This
depth is significantly
shallower for aragonite
than for calcite, because
aragonite is more soluble
in seawater than calcite.
• Pronounced shoaling from Atlantic through the Indian to the Pacific Oceans.
• The higher DIC/TA in the deep waters of the Indian and Pacific.
• DIC > TC, due to respiration processes and water circulates along Deep Conveyor Belt.

IMPRINTS OF
ANTHROPOGENIC
CO2 ON THE
OCEANS
Fig.8.
Representative
sections of
anthropogenic
CO2(µmol kg-1)
from (A) the
Atlantic, (B)
Pacific, and Indian
(C) oceans.
Source: Sabine et al. (2004)

Fig.9. Vertical distributions of
anthropogenic CO2 concentrations in
mol kg–1 and the supersaturation/
undersaturation horizons for
aragonite and calcite along north-
south transects in the (A)
Atlantic, (B) Pacific, and (C) Indian
Oceans.
Present-day (solid line)
Preindustrial (dashed line)
Present saturation
horizon is same as
pre-industrial
80-150m
100-200m
Aragonite-: 30-100m
Calcite-: 40-100m

VOLCANIC CO2 VENTS
IMPACTS
Fig.10. Variation in pH, cover
of algae and abundance of
species at CO2 vents.
calcareous (triangles) and
noncalcareous
algae (circles) is shown.
Source: Jason M. Hall-Spencer (2008)
PercentageAlgalCoverpH(TotalScale)

c
Fig.11. Posidonia
oceanica with heavy
overgrowth of
Corallinaceae at pH 8.2
(a) and lacking
Corallinaceae at mean
pH7.6.
(b); arrow indicates
bubbles from the CO2 vent
field.
(c) Sea-grass shoot density
and amount of CaCO3 on
leaves growing at differing
pH levels.
Source: Jason M. Hall-Spencer
(2008)

IMPACTS OF SHIPS
Fig.12. Calculated surface water pH changes arising
from shipping-derived inputs of SOX and NOX.
• The largest effects of SOX
and NOX are in parts of the
Northern Hemisphere 85%.
•Annual acidifications of
0.0014, 0.00046, and
0.0008 for the North Sea,
Baltic Sea and South China
Sea, respectively.
• The Baltic Sea has a lower
buffer capacity, making it
especially sensitive to
strong acids.
•A maximum annual
acidification of 0.0004 pH.
Source: Hassellöv et.al. (2013)

Fig.13. Calculated shipping-derived
acidification (ΔpH) with
surface water (a) pCO2 (30,688
data points)
(b) SOX , NOX (30,675
data points).
• The calculated near-coastal
seasonal acidification of
0.0015–0.002 pH
• Heavily trafficked trade routes
more acidic, and may
contribute to local acidification.
•Shipping acidification could be
a concern where high traffic
occurs near fisheries or
biodiversity.
Source: Hassellöv et.al. (2013)

IMPACT ON CALCIFYING ORGANISMS
 Reduced calcification and growth of the corals.
 The most absolute impact is the decrease in the linear extension rate and
skeletal density of coral colonies.
 Loss of structural complexity- which will affect the reefs to absorb wave
energy and thereby impairs coastal protection.
 Mass coral Bleaching and loss of rugosity.
 Increased erosion by the activities of grazing fishes such as parrotfish
which removes carbonates from low density substrates.
 Reduced larval output from reefs.
 Loss of habitat quality and diversity.
 Loss of ecological resilience.

Stony coral
Sea urchins
Pteropods
Coralline algae
Calcium carbonate part
Coral skeleton
Skeleton & test
Shell
Component of fronds
Fish
Ear bones and other
structures
Organism

• 10-50% decrease in the calcification rate of reef-building corals and
coralline algae. (Kleypas and Langdon,2006)
• The calcifying macro algae like coralline red and calcifying green
contains high Mg calcite and has shown slow calcification rate.
• Rhodoliths calcification decreased as much
as 250% in mesocosms and successful recruitment by
coralline algae was diminished. (Kuffner et al.,2008)
• Mollusks are reef organisms in shelled forms it is expected
that some species will produce thinner shells and suffer
reduced recruitment rates. ( Green et al.,2004,Miller et al.,2009)
• One of the most interesting effects of OA concerns “endolithic” algae
that bore into reef skeletal material. At double CO2 level, these algae bore
more deeply into skeletal material, dissolving nearly 50% carbonate in
oceans.
(Tribollet et al.,2009)
Mollusks
Rhodoliths
EFFECTS ON CALCIFYING ORGANISMS

Echinoderms
• The greater solubility of high Mg calcite
skeletons of echinoderms suggests that
they are highly vulnerable to OA.
(Kurihara 2008,Miles et al.,2007)
• Calcareous benthic foraminifera
produces bulk of carbonate sands
in shallower environment and are
sensitive to high CO2
concentrations.
(Bernhard et al.,2009)

Major planktonic calcifers
Coccolithophores
Foraminifera
Pteropods
algae
protists
snails
~ 200 calcite days
~ 30 weekscalcite
~ 32 months to
year?
aragonite
Extant
species
Mineral
form
Generation
Time

• Characteristics:
– Free drifting photosynthetic Phytoplankton
(phylum Haptophyta)
– One of the most abundant marine calcifying
phytoplankton
– Building of calcium carbonate scales
(coccoliths)
Ca2+ + CO3
2- ↔ CaCO3
Ca2+ + 2HCO3
- ↔ CaCO3 + H2O + CO2
• Occurrence:
– Mostly in upper layers of sub polar regions
– Nutrient poor and mild temperature waters
COCCOLITHOPHORES

E. huxleyi
G. oceanica
C. braarudii
aarudii
C. . C.quadriperforatus
pH DISRUPTS
SHELL
FORMATION
Ambient pH
Decrease in pH
Coccolithophores
largest producer of
calcite on Earth
Source-Riebesell et al. 2000
Langer et al. 2006
Coccolithophore bloom in the English
Channel off the coast of Plymouth
[NASA Image]

FORAMINIFERA
SHELLED PTEROPODS
(single-celled protists)
 -4 to -8% decline in calcification at pCO2= 560 ppm
 -6 to -14% decline in calcification at pCO2= 780 ppm
Source-Bijma et al. (2002)
(planktonic snails)
Shell dissolution in a live pteropod (Clio pyramidata) Source-Orr et al. (2005)

Loss of marine biodiversity
Coral reefs harbor more than 25% of the ocean’s biodiversity –
provide a refuge and feeding ground for countless marine
organisms.
> 50% of all corals reefs are in cold, deep waters – more impacted
by ocean acidification.
(Source-NOAA)

Coral Bleaching
Unbleached coral Bleached coral
CaCO3 → CaO + CO2
Coral Bleaching is a stress condition in coral reefs that
involves the breakdown of zooxanthellae.
Source: buceandoelmundo.wordpress.com

(A) Linkages between the buildup of
atmospheric CO2 and the slowing of coral
calcification due to ocean acidification.
(B)Temperature, [CO2] atm, and carbonate-ion
concentrations reconstructed for the past
420,000 years.
(O. Hoegh-Guldberg et al. 2007)
Coral Calcification Scenario

• Reduction in the resilience of Caribbean forereefs as coral growth rate declines by 20%.
• Reef recovery is only feasible above or to the right of the unstable equilibria (open squares).
• The “zone of reef recovery”(pink) is therefore more restricted under reduced coral growth rate
and reefs require higher levels of grazing to exhibit recovery trajectories.
Shift in Equilibrium of corals
(Source: O. Hoegh-Guldberg et al. 2007)

• Changes in coral community calcification rate in the Biosphere 2 coral reef mesocosm as a
function of decreasing aragonite saturation state.
• Note that once Ωarg value reached a value of 1.0-2.0 the coral community shifted from net
calcification to net dissolution.
Change in coral calcification rate with Aragonite
Saturation
Fig. Atmospheric pCO2 levels that roughly correspond to Ωarg values
(Langdon et al., 2003)

(A) Reef slope communities at Heron Island.
(B) Mixed algal and coral communities associated with
inshore reefs around St. Bees Island near Mackay.
(C) Inshore reef slope around the Low Isles near Port
Douglas.
Plot showing the variation of calcification (grams
per square centimeter per year) in Porites corals
over time. (modified from De’ath et al, Science,
2008).
The Great Barrier Reef Scenario
• Calcification has declined with 14.2%,
from 1.76 g/cm2/y to 1.51 g/cm2/y.
Source: (O. Hoegh-Guldberg et al. 2007)
Coral Reef Scenarios CRS-A, CRS-B, and CRS-C from the
Great Barrier Reef

Calculated changes in reef building of coral reefs worldwide at four different atmospheric
pCO2 stabilization levels, based on the combined changes in saturation state and temperature
on coral community calcification. The values are expressed as a percentage of pre-industrial
calcification rates ; PIR=Pre-Industrial rate; TGgross = temperature dependent Gross
calcification. Note that this calculation assumes constant coral cover=50%
Change in Reef Building of Corals
(Silverman et al. (2009)

Fig. Effects of experimental ocean acidification
(CO2level) and warming on three key performance
variables of three major coral reef builders:
Effects of experimental
ocean acidification
• (A–C) crustose coralline algae
(CCA,Porolithononkodes),
• (D–F) branching Acropora (A. intermedia), and
• (G–I) massivePorites(P. lobata).
• Gray and black bars show low- and high-
temperature treatments, respectively.
• Levels of CO2 represented the present-day
control condition (380 ppm atmospheric CO2)
and projected scenarios for high categories IV
(520 –700 ppm) and VI (1000 –1300 ppm) by
the IPCC.
(Source: Anthony et al.)

Impact pathway for OA
Socio-Economic
Activity
CO2 Emissions
Ocean
Acidification
 Food Webs
 Fish Stocks
Coral Reefs
 Fish Catch
 Aquaculture
 Tourism
 Coastal
Protection
 Biodiversity
 Population
 Income
 Welfare
 Distribution
 Vulnerability
 Food Security
 Adaptation
Marine
Ecosystems
Ecosystem
Services
Socio-economic
impacts
Source: Moore et al. (2011)

Socio-Economic Impacts
Economic value of corals :
• Act as a habitat and nursery for
commercial fish stocks.
• Act as a natural barrier for coastlines.
• Provides recreation and tourism
opportunities
 The global economic value associated with
reefs is of the order of $30 billion per year.
 Loss of coral reefs will amount to a loss of
tens of billions of dollars.
 The economic value of damage to coral reefs
has been estimated and losses were found to
be of the order of 0.18% of global GDP in
2100.(European Science foundation)

Global Economic Losses
Source: Brander et al. (2009)

Ecosystem Effects of Ocean Acidification in Times
of Ocean Warming: A Physiologist’s View
Portner.et.al., 2008

Overview of Processes and Mechanisms Affected By CO2
In a Generalized Water-breathing Animal

Heat Tolerance Of The Edible Crab Cancer Pagurus Under
Normocapnia And Hypercapnia
1. Discontinuities in the curve depicting arterial oxygen tensions (pO2) under normocapnia
were identified as thermal limits.
2. Highly elevated CO2 levels (1% hypercapnia) cause heat tolerance to decrease
dramatically by about 5 C.

Conceptual Model of How Ocean Acidification, Hypoxia
And Temperature Extremes Interact Mechanistically.
Temperature

Meta-analysis reveals negative yet variable effects
of ocean acidification on marine organisms
Kristy j. Kroeker. et.al., 2010

Effect of Near-future (2100) Ocean Acidification on
Different Response Variables Of Marine Organisms from
Weighted, Random Effects Meta-analyses
Kristy j. Kroeker. et.al., 2010

Impact of Anthropogenic Atmospheric Nitrogen and
Sulphur Deposition on Ocean Acidification and the
Inorganic Carbon System
 Basic Principles of The Effects of Atmospheric C, S and N Deposition
on Seawater Chemistry
Scott C. Doney. et.al., 2007

Model-estimated Anthropogenic (1990–2000 Minus Preindustrial)
And Preindustrial Atmospheric Deposition Fluxes
Integrated anthropogenic
deposition Teq/y (preindustrial)
Flux Global Ocean-only Model Observed
138 0.10 to 0.20
4.11(0.00) 1.99(0.00) 0.00 to 0.03 0.02
1.84(1.18) 0.67(0.73) 0.00 to 0.03 0.02
2.21(0.58) 0.78(0.49) 0.00 to 0.03 0.01
-2.15(-2.34) -0.24(-1.71) -0.01 to +0.01
-10.37(-2.34) -4.22(-1.71) -0.01 to +0.01
Scott C. Doney. et.al., 2007

OCEAN ACIDIFICATION
MITIGATION
Source: Adelsman and Binder, 2012

SYNOPSIS OF MITIGATION STRATEGIES BY EUROPEAN SCIENCE FOUNDATION
AND UNITED STATES BLUE RIBBON PANEL ON OCEAN ACIDIFICATION
• Co-ordinating at various levels (local to global scale) to reduce CO2 emissions and sharing
research for a sustainable policy development
• Strengthening monitoring abilities: more field and lab studies
• Using Earth’s past to understand OA: PETM
• Understanding biogeochemical feedbacks and relationships with OA
• OA Integrated Climate models with different feedbacks
• Understanding the relationship with climate change and the cost additions in mitigation
Monitoring BuoyLocal air emissions Wave Glider

• Adopting measures to reduce land based
contributions to OA: nutrients & organic carbon
• Developing strategies keeping in mind the socio-
economic impacts on natural resources and human
communities: Communicating with the stake-
holders, fund providers and other researchers
• Adapting to the changing OA: shellfish farms &
phytoremediation
Seaweed growing on oyster longlines: Phytoremediation
Waste water dumped directly into water bodies
Centre for Microbial Oceanography, Hawaii

IRON FERTILIZATION
• Increase of biological production by addition of iron to the upper ocean layer
• “Iron Hypothesis” : Iron acts as a fertilizer in increasing the growth of
phytoplankton in high-nutrient, low-chlorophyll (HNLC) regions thereby
increasing the ability of oceans to store more atmospheric CO2
After Martin, 1990
• Commercially supported as Carbon Credit generation method
• Method Adopted: Zero phosphate concentration in near surface ocean denoting
the maximum macronutrient decrease by iron fertilization
• Scenarios:
• A2_emission
• A2_emission + Ocean Iron Fertilization (OIF)
• A2_conc + OIF: generates carbon credit
Source: Cao and Caldeira, 2010

OBSERVATIONS and RESULTS
Source: Cao and Caldeira, 2010
Slight mitigation of surface
ocean acidification at the
cost of increased deep ocean
acidification
Fig: Simulated surface ocean pH
Fig: Simulated temporal evolution of pH
Deep Ocean
Accelerated acidification
Shoaling of saturation zones
More effect in Southern Oceans
Surface Ocean
Minor mitigation effect
(lowering of pH reduced by 0.06
units)
Lag by a decade

LIMESTONE ADDITION TO UPWELLING REGIONS
• Enhancement of CO2 absorption
from the atmosphere
• Partial Reversal of OA
CO2(g) + H2O(l) → H2CO3(aq)
H2CO3(aq) → H+ + HCO3
-
CO3
2- + H+ → HCO3
-
_____________________________
H2O + CO2 + CO3
2- → 2HCO3-
CaCO3 → Ca2+ + CO3
2-
______________________________
CaCO3 + H2O + CO2 → Ca2+ + 2HCO3-
Source: Harvey, 2008
Fig: Distribution of the limestone powder addition rate for total application rate of 4gt/a

OBSERVATIONS
pH recovery of 0.06 by 2200 and 0.12 by 2500
Scenario 1: global CO2 emission grows to 17.5 Gt C/a in 2100 and then declines at
1%/a
Scenario 2: global CO2 emission grows to 7.5 Gt C/a by 2010, return to 2010 level by
2020 and continue to go down to 0 by 2100

RESULT AND DISCUSSION
Feasibility of the process
• Economic cost: 40-45 billion dollars per annum for 4 Gt/a application rate
• Energy requirements in terms of transport, crushing and sprinkling of limestone
• Comparisons with iron fertilization: Limestone process dependent on inorganic
chemical reactions.
• Increase in ocean surface albedo: slight cooling
• Decrease of solar radiation penetration: reduce biological pump strength
Switch from the increasing CO2 path to one with zero emission
Preindustrial pH level 8.31
pH by 2100 with Zero emissions : 8.12
pH by 2100 if peak emission is 17.5 Gt C/a : 7.78
Addition of Limestone at 4 Gt/a : difference between Pre-industrial
level and minimum pH restored by 20% by 2200 and 40% by 2500

• Clear evidence of Ocean Acidification
• Main Cause: Anthropogenic CO2 emission
• Impacts on marine ecosystem and shell organisms
• Economic impacts on fish industry
• Mitigation strategies needed in collaboration with climate models
CONCLUSION
OCEAN ACIDIFICATION:
A CHALLENGE
THAT
“CAN” AND “MUST BE” MET

REFERENCES
Adelsman, H. and Binder L.W., 2012, Washington State Blue Ribbon Panel on Ocean Acidification : Ocean Acidification: From
Knowledge to Action, Washington State’s Strategic Response. Washington Department of Ecology, Olympia, Washington.
Publication no. 12-01-015.
Harvey, L.D.D., 2008, Mitigating the atmospheric CO2increase and ocean acidification by adding limestone powder to
upwelling regions, JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 113
Cao, L., Caldeira. K., 2010, Can ocean iron fertilization mitigate ocean acidification?, Climatic Change, DOI 10.1007/s10584-
010-9799-4
Makarow et. al, 2009, Impacts of Ocean Acidification, Science Policy Briefing, (www.esf.org).
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