BRS SEMINAR SERIES PRESENTS: Friday 8 July Ocean uptake of CO2: Are the Oceans Acidifying? Dr Steve Widdicombe, Plymouth Marine Laboratories, UK This presentation will introduce the process of ocean acidification, highlight some of the key environmental concerns and discuss some of the mitigation strategies that have been suggested. With world primary energy demand projected to rise at an average of 1.7% annually over the next 30 years this means an increase in the release of CO 2 . Of all the predicted impacts attributed to this inevitable rise in atmospheric CO 2 concentration (and the associated rise in temperature), one of the most pressing is the acidification of surface waters through the absorption of the atmospheric CO 2 and its reaction with seawater to form carbonic acid. It is predicted that this process may lead to a surface ocean pH reduction of 0.7 units by the end of the century. It is clear that the growing emissions of CO 2 from human processes could pose a distinct threat to the global environment. However quantifying the consequences of CO 2 release is problematic as many physical and biogeochemical processes combine to create a complex set of interactions. 11.00am - 12:00noon (morning tea at 10:45am) Edmund Barton Conference Centre (in the courtyard) Edmund Barton Building Kings Avenue, Canberra Bookings not required. Parking can be a problem, we suggest taking a taxi. For further details, please call the BRS Seminar Coordinator on 6272 3440. For further information on BRS Seminars or to obtain papers/presentations supplied by previous seminar presenters, please visit our website at: www.brs.gov.au/brsseminars
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B R S S E M I N A R S E R I E S P R E S E N T S :
Friday 8 July
Ocean uptake of CO2:Are the Oceans Acidifying?
Dr Steve Widdicombe,Plymouth Marine Laboratories, UK
This presentation will introduce the process of ocean acidification, highlight someof the key environmental concerns and discuss some of the mitigation strategiesthat have been suggested. With world primary energy demand projected to rise atan average of 1.7% annually over the next 30 years this means an increase in therelease of CO2. Of all the predicted impacts attributed to this inevitable rise inatmospheric CO2 concentration (and the associated rise in temperature), one ofthe most pressing is the acidification of surface waters through the absorption ofthe atmospheric CO2 and its reaction with seawater to form carbonic acid. It ispredicted that this process may lead to a surface ocean pH reduction of 0.7 unitsby the end of the century. It is clear that the growing emissions of CO2 from humanprocesses could pose a distinct threat to the global environment. Howeverquantifying the consequences of CO2 release is problematic as many physical andbiogeochemical processes combine to create a complex set of interactions.
11.00am - 12:00noon (morning tea at 10:45am)Edmund Barton Conference Centre (in the courtyard)
Edmund Barton BuildingKings Avenue, Canberra
Bookings not required.Parking can be a problem, we suggest taking a taxi.
For further details, please call the BRS Seminar Coordinator on 6272 3440.
For further information on BRS Seminars or to obtain papers/presentations supplied byprevious seminar presenters, please visit our website at: www.brs.gov.au/brsseminars
Reviewing the Impact of Increased Atmospheric CO2 onOceanic pH and the Marine Ecosystem:
“Ocean Acidification”
Dr Steve WiddicombePlymouth Marine Laboratory
Benthic Ecologist
I have worked at PML for the past 15 years
Main interests are the factors that affect the communities that live in/on the seafloorand the ecosystem functions these communities perform.
Particular area of expertise is the use of large experiments to explore theseinterests.
The Plymouth Marine Laboratory [PML] is an independent and impartial collaborativecentre of the UK Natural Environment Research Council [NERC].
First involvement with ocean acidification was 4 years ago through a EuropeanNetwork of Excellence “CO2 GeoNet”
I now run 2 large interdisciplinary projects exploring the potential impacts of oceanacidification and the ecological risks associated with geological storage.
Carbon in the Ocean
Pre industrially, the oceansand the organisms that live inthem contained about 38 000Gt C (1 Gt = 1015 grams or 1billion tonnes)
Oceans are a carbon sink andtake up 2 Gt C per year
This 95% of all the carbon thatis in the oceans, atmosphereand on land.
6 Gt C per year released into the atmosphereby human activities
Atmospheric concentrations are higher today than at any timefor at least the last 420 000 years
Burning fossil fuels is releasing CO2 that wouldotherwise be locked up in geological reservoirs.
About one half (48%) of all the CO2 produced by fossil fuel burningand cement production in the past 200 years (1800 – 1994) hasbeen absorbed by the oceans.
A total of 118 ± 18 Gt C (1800 – 1994)
Today that figure is nearer 140 Gt C(over 500 Gt CO2)
Human impact on the carbon cycle
Oceanic AcidificationAtmosphere
CO2 (g) CO2 + H2O ´(H2CO3)´ HCO3
- + H+ ´ CO32- + 2H+
Surface Ocean
CO2 dissolves into the seawater to form Dissolved Inorganic Carbon(DIC) which consists of:
1. aqueous CO2 (including carbonic acid) – 1%
2. bicarbonate HCO3- - 91%
3. carbonate CO32- - 8%
All 3 forms of DIC are important for biological processes (e.g.photosynthesis and calcification)
DIC operates as a natural buffer to the addition of hydrogen ions –known as the “carbonate buffer”
BUT we now know there is a limit to how much CO2 the carbonatebuffer can deal with.
Henry’s Law
Oceanic pH
Acid solutions have an excess of H+ ions and a pH less than 7
Alkaline solutions have an excess of OH- ions and a pH more than 7
The term pH describes the acidity of a liquid.
pH = -log10[H+]
H20 _ H+ + OH-
Concentration of H+ and OH- are roughly equal (10-7 mole per litre)This means a neutral solution has a pH = 7
This measure is negative logarithmic – if H+ concentration increase10 fold, pH decreases by one unit.
Compares with measurements / estimates of15-150 mmol N .m-2.y-1. (Lohse 93,96)
2000 simulation
WCS simulation
Difference in denitrification loss
WCS - 2000
Effects on larger organisms
Decreased motility, inhibition of feeding,
reduced growth, reduced recruitment,
respiratory distress, decrease in population size,
shell dissolution, mortality
increased susceptibility to infection
destruction of chemosensory systems
Effects of Low pH on Zooplankton: the Food of Fish
Yamada & Ikeda 1999; Heath 1995; Shiramura et al. 2002; Kurihara et al. 2004
Evidence to indicate that marine zooplankton(crustacea) passing through plumes of CO2enriched seawater suffer high mortalities – butvery little research
Some zooplankton have calcium carbonate shells(molluscs) and will be vulnerable. This pteropodis an important part of the Antarctic food web
Reduced fertilization of copepod eggs at CO2
levels beyond 1000 ppm (2100 worst casescenario)
Limacina helicina antartica
Adult female copepod bearing eggs
Crustacean zooplankton
Impact on Fish and Squid
Portner and Reipschlager (1996); Portner et al. (2004)
Squid are an important food resourcefor humans, whales etc.
At 3 fold increases in atmospheric CO2, fish andother complex animals are likely to havedifficulty reducing internal CO2 concentrations,resulting in accumulation of CO2 andacidification of body tissues and fluids(hypercapnia)
The effects of lower level, long term increases inCO2 on reproduction and development of marineanimals is unknown and of concern
Squid very sensitive because of their highenergy and O2 demand for jet propulsiondecrease in pH of 0.25 having drastic effects(reduction of c. 50%) on their oxygen carryingcapacity
Effects on calcifyingorganisms
Coccolithophores
Others include: Foraminifera, echinoderms and molluscs
and Corals
Coccolithophores: Important Primary Producerson European Shelf Seas
Change in biogeochemistryand ecosystem
Holligan 1993; Archer et al. 2003
Extensive blooms (often 100,000’s km2)of these calcite forming phytoplanktonoccur on shelf seas
Important role in the global carbon cyclethrough the transport of calcium carbonateto deeper waters and sediments
Coccolithophores aremajor producers ofdimethyl sulphide (DMS)to the atmosphere –thought to be important incloud formation andhence a negativefeedback to climate
Effects of CO2 on Coccolithophores
Gephyrocapsa oceanica
Riebesell et al. Nature (2000)
300 ppm
780-850 ppm
Emiliania huxleyi
pCO2
Reducedcalcification
Coccolithophore model
depth
Julian day
Year 1WeakerstratificationConstant at 30m,
Year 2Strongerstratification,Warmer withdeepening out ofthe euphotic zone
Simulated coccolithophore biomass, compares withobservations of 44 mg C.m-3 at surface, (Burkill, 2002;Widdicombe, 2002).
Based on Tyrrell & Taylor (1996) and Merico et al (2004)
Coccolithophore results
0
400
800
1200
1600
Jan Feb Apr Jun Aug Oct Dec Feb Apr Jun Aug Oct Dec
Y2000
Y2050
Y2100
Ywcs
0
5
10
15
20
Jan Feb Apr Jun Aug Oct Dec Feb Apr Jun Aug Oct Dec
Y2000
Y2050
Y2100
Ywcs
Á Coccolithophore cell biomass (mgC.m-2)
Marked inhibition of coccolithophores is seenwith decreasing pH.
Inhibition strength is sensitive to the physicalconditions prevailing
Stronger light and nutrient limitation in year 2decrease the relative effect of calcificationinhibition
ÁNumber of liths per cell
Inhibition correlates with the degree of lithcoverage and hence the parameterisation ofmortality and grazing relative to the lithcoverage.
Parameterisation penalises <10 liths.cell-1
Warm Water Coral ReefsOnly 1.28 million squarekilometres (less than 1.2%of the worlds continentalshelf area)
BUT many millions ofpeople directly dependanton healthy coral reefs(tourism and fisheries).
Highly diverse ecosystem.
Coral reefsoccur in warm,alkaline, sunlitwaters with higharagonitesaturation.
Corals form a powerful mutualisticsymbiosis with tiny dinoflagellate
algae known as zooxanthellae.
Sitting in the tissues, the algalsymbionts photosynthesize and passmost of their production to the coral.
What are coral reefs ?
In return, the animal provides inorganic nutrients such asammonia and phosphate – from their waste metabolism.
The fate of corals
95% correlation with increases in seatemperature (1-2% above long-termsummer sea temperature maxima) andbleaching.
Backed up experimentally
Almost 30% of warm water corals have disappeared sincethe beginning of the 1980s
Largely due to increasingly frequent and intense periods ofwarm sea temperatures
Required Aragonite saturation for “healthy” coral growth – Average min/max 3.28 – 4.06
High atmospheric CO2 is compounding the problem bylowering the aragonite saturation state of seawater
If atmospheric CO2 concentrations double, calcification rates coulddecrease by 10-30% (Gattuso et al., 1999; Kleypas et al., 1999b).
Some recent studies even suggest a decrease of 54%.
Coral loss = Financial loss
Globally, corals support millions of people through subsistence foodgathering and tourism.
Studies have been based on global warming only.
(Hoegh-Guldberg & Hoegh-Guldberg, 2004)
Reef associated revenue / goods contribute 68% of the grossregional product (AU$ 1.4 billion)
Most dependent region - North Queensland.Of the AU$900 million tourism revenue,AU$800 million was associated with having ahealthy coral reef.
Reef degradation (600ppm by 2100) will cost the local economies ofcoastal Queensland a minimum of AU$2.5 billion over 19 years (2001-2020).
If atmospheric CO2 is higher (800ppm by 2100) financial cost could beas high as AU$14 billion.
The Caribbean
Hawaii
Caribbean reefs provide annual net benefits (fisheries, divetourism and shoreline protection) of between US$ 3.1 billion andUS$ 4.6 billion (Burke et al, 2004)
By 2015, loss of income due to reef degradation, thought to beseveral hundred million dollars per year.
Estimated that coral reefsgenerate US$ 364 millioneach year.