Seas turning sour
Effects of increased CO on
Emilania huxleyi and Gephryocapsa
oceanica: growth and structure are
Riebesell et al, 2000.
calcification rates, slowing down the growth rates and decreasing
Ocean acidification is the change in ocean chemistry driven by
the structural strength of calcifying organisms.
the uptake of carbon, nitrogen and sulfur compounds by the
ocean from the atmosphere. Oceans are an important reservoir
Furthermore, as the concentration of hydrogen ions in
for CO , absorbing a significant quantity (one-third according to
the oceans increases the pH decreases. The uptake of
Sabine et al. 2004) produced by anthropogenic activities and
atmospheric carbon dioxide is occurring at a rate exceeding
effectively buffering climate change. However as atmospheric
the natural buffering capacity of the ocean, and the pH of the
carbon dioxide increases, the concentration of hydrogen ions
ocean surface waters has decreased by about 0.1 units since
in the ocean increases, the concentration of carbonate ions
the beginning of the industrial revolution. If current carbon
decreases, the pH of the oceans decreases and the oceans
dioxide emission trends continue, the ocean wil continue to
become less alkaline – this is the process know as ocean
undergo acidification, to an extent and at rates that have not
acidification. While there is uncertainty about many aspects
occurred for tens of million of years (McLeod et al, 2008).
of climate change, the geochemical processes driving these
Ocean acidification is largely an invisible, chronic environmental
changes are highly predictable.
problem. It is also a very recently recognized issue so there
is limited empirical data on which to base the identification of
What is happening?
Seawater absorbs CO to produce carbonic acid (H CO ),
bicarbonate (HCO -) and carbonate ions (CO 2-). These
What is at stake?
carbonate ions are essential to the calcification process that
A doubling of the concentration of atmospheric carbon dioxide,
allows certain marine organisms to build their calcium carbonate
which could occur in as little as 50 years, could cause major
shells and skeletons (e.g. hard tropical corals, cold water corals,
changes in the marine environment, specifically impacting
certain types of plankton, lobsters, mussels, etc). However,
calcium carbonate organisms, such as corals or calcifying
increases in atmospheric CO levels lead to increases in the
plankton. This could in turn have knock-on effects cascading
concentration of carbonic acid and bicarbonate ions, causing
through the food chain, causing damage to very valuable marine
a decrease in the concentration of carbonate ions. This affects
ecosystems. Organisms that could be seriously affected include:
InternatIonal unIon for conservatIon of nature
Reef-building corals - Calcification rates of tropical corals
between seagrasses and macro-algae
and coralline algae may decrease by 30% over the next 30-50
Ocean acidification is thus a major threat to the marine
years. The growth of reefs as geological structures will be
environment, which could have major impacts on marine
affected by both reduced accretion and increased erosion.
ecosystems, commercial fisheries and even the climate through
Reduced skeletal growth may be manifested as slower growth
changes in plankton communities. The long time-lags inherent
rates, or weaker coral skeletons that are more susceptible to
in the marine carbon cycle put a penalty on delaying limits on
storm damage. Coral reefs are hugely important sources of food
carbon dioxide emissions, and a premium on early action if the
and revenue for hundreds of millions of people, and also support
worst damages associated with ocean acidification are to be
multi-billion tourism and fisheries industries.
avoided.To combat the worst effects of ocean acidification, a
two-pronged mitigation and adaptation approach is needed to
buy time. This includes reducing greenhouse gas emissions
at source, and improving management of marine resources
to boost the resilience of marine ecosystems to allow them to
recover from acidification impacts.
What is IUCN doing?
IUCN is involved in the European Project on Ocean Acidification
(EPOCA), a collaboration between top European research
groups aimed at filling gaps in our understanding of the effects
and implications of ocean acidification. It aims to document
changes in ocean chemistry and biogeography across
space and time and to determine the sensitivity of marine
organisms, communities and ecosystems to ocean acidification.
Laboratory and field-based experiments will be used to
Cold water corals – Up to 70% of deep-sea corals are
quantify biological responses to ocean acidification, assess the
predicted to be undersaturated by 2100. This means their
potential for adaptation, and determine the consequences for
growth rate and structural strength would be severely impacted.
biogeochemical cycling. They will assess uncertainties, risks and
Cold water corals provide crucial habitats for many important fish
thresholds in the marine environment. IUCN plays an important
role in the EPOCA Reference User Group, and will be critical in
communicating results from this cutting edge research across
Calcareous benthic invertebrates (including lobsters,
mussels and scallops) – There are measurable impacts on
growth rates and survival rates of echinoderms and gastropods
Moreover, the IUCN Climate Change and Coral Reefs Working
at 560ppm atmospheric CO , which is the projected levels
Group (IUCN-CCCR) is involved in the Honolulu Declaration
for 2050. Impacts include slower growth rates and lower final
on Ocean Acidification and Reef Management, a declaration
weights. This would imply losses of commercially important
made by a group of global ocean experts in August 2008 at
species such as lobsters, mussels and scallops.
a workshop convened by The Nature Conservancy in Hawaii.
Two major strategies are identified that must be implemented
Planktonic calcifiers (such as coccolithophores, foramnifera, urgently and concurrently to mitigate the impacts of climate
euthecosomatous and pteropods) – Experiments have shown
change and to safeguard the value of coral reef systems: 1)
that 5 out of 6 species show 6-60% decreases in calcification
limit fossil fuel emissions; and 2) build the resilience of tropical
with decreases in pH. Planktonic calcifiers play a major role in
marine ecosystems and communities to maximize their ability to
the Earth’s Carbon cycle by absorbing CO from the atmosphere
resist and recover from climate change impacts. IUCN-CCCR
and retaining it in the oceans as well as providing food for
members were instrumental in writing the declaration, and IUCN-
commercially important fish and cetaceans. Effects on plankton
CCCR is publishing a guide for coral reef practitioners to manage
communities could have serious knock-on effects cascading
reefs for resilience to ocean acidification.
through the entire marine food chain.
Seagrass - Seagrasses use CO for photosynthesis rather than Gabriel Grimsditch firstname.lastname@example.org
bicarbonate like most marine macroalgae, so certain species
IUCN CCCR - www.iucn.org/cccr/index.cfm
could benefit leading to ecological regime shifts. Changes
IUCN Climate Change Initiative - www.iucn.org/climate
may occur in the competition between seagrass species and
InternatIonal unIon for conservatIon of nature
IUCN (International Union for Conservation of Nature) is the world’s oldest and largest global environmental network. IUCN is a democratic membership
union with more than 1,000 government and NGO member organizations, and almost 11,000 volunteer scientists and experts in some 160 countries.
IUCN’s work is supported by over 1,000 professional staff in 60 offices and hundreds of partners in public, NGO and private sectors around the world.
IUCN helps the world find pragmatic solutions to our most pressing environment and development chal enges by supporting cutting-edge research;
managing field projects all over the world; and bringing governments, NGOs, the UN, international conventions and companies together to develop policy,
laws and best practice. www.iucn.org