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What will you be doing in lab this week? Ocean Acidification lab

What is Ocean Acidification? https://www.youtube.com/watch

?v=Wo-bHt1bOsw

Blowing bubbles What are you exhaling with every

breath? Why does dissolving CO2 in water

result in a change of pH?

Dissolving shells What are (most) shells made of? Why do shells dissolve in low pH?

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What role do the oceans play in climate?

Exchange and transfer of heat Oceans carry heat from the tropics (equator) to the poles, to

maintain Earth's temperature

Oceans are main reservoirs of readily available carbon dioxide (CO2) The cold, deep water in the ocean is the main active reservoir of

dissolved CO2

Exchange and transfer of CO2 (and O2) Change in ocean pH

Status of Ocean Acidification

~1/3 of fossil-fuel CO2 dissolves in ocean

Between 1751 and 1994 surface ocean pH is estimated to have decreased from approximately 8.2 to 8.1

Logarithmic scale of pH; approximately a 25% increase in H+

Estimated that it will drop by a further 0.3 to 0.5 units by 2100

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What is pH? pH is a measure of the acidity or basicity of a

solution

Defined based on the activity of dissolved hydrogen ions (H+)

Measured by pH scale pH = -log [H+] higher [H+] = lower pH

0–6 = acid, 7 = neutral, 8–14 = alkaline Each is a power of 10 difference in pH

pH scale

Low pH = lots of H+

High pH = few H+

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Oceans in a High CO2 World

Oceans absorb and release CO2

More CO2 in the atmosphere, more CO2 in the oceans

CO2 reacts with water to form an acid

H+ falls off into water

pH goes down

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Oceans in a High CO2 World

When CO2 dissolves, it reacts with water to form a balance of chemical species: dissolved free carbon dioxide (CO2(aq)), carbonic acid (H2CO3), bicarbonate (HCO3

-1) and carbonate (CO3-2)

The ratio of these species depends on temperature and pH and temperature

Dissolving CO2 increases [H+]

Lower pH

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CO2 chemistry in seawater

The equilibrium reaction for CO2 chemistry in seawater that best captures its behavior is:

CO2 + H2O + CO3-2 <==> 2HCO3

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(carbon dioxide) (water) (carbonate) (bicarbonate)

Which direction does the reaction move given the decrease in pH observed since the Industrial Revolution?

CO2 + H2O + CO3-2 _______ 2HCO3

-1

What happened to the concentration of bicarbonate (HCO3-1) in

the oceans?

What has happened to the concentration of carbonate (CO3-2)

in the oceans?

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Impacts of ocean acidification

Negative impacts on organisms that build shells, skeletons or exoskeletons of calcium carbonate (CaCO3)

Loss of biodiversity and ecosystem function Extinction of marine organisms WATCH: https://www.youtube.com/watch?v=GL7qJYKzcsk

Reduced survival of marine organisms Larva or juveniles Commercially important fish and shellfish Decrease in fertilization and settling success

Changes in food web structure Reduction or removal of important species Reduction in photosynthetic potential?

Deafness in whales?

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Why does increasing the dissolved CO2 concentration in seawater affect shell building in marine organisms?

The calcification reaction that forms shells, exoskeletons, and the skeleton of coral reefs from CO2 is:

Ca2+ + CO32- <==> CaCO3

(calcium) (carbonate) (calcium carbonate)

At low pH, less carbonate (CO32-)

“Harder” to form shells, exoskeletons and coral reef structures

In what direction will the dominant (or net) calcification reaction that forms coral reefs proceed at low ocean pH values?

Ca2+ + CO32- ____________ CaCO3

Dissolution of calcium carbonate hard parts

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Impacts of Ocean Acidification Impacts on organisms that build shells and plates out of calcium

carbonate (CaCO3) More acidic (lower pH) = less carbonate

Vulnerable organisms: Bivalves (mussels, clams, oysters)

What’s happening to local shellfish industry? https://www.youtube.com/watch?v=x7MpI9dZIjk

Coccolithophorids (phytoplankton) Pteropods, foraminifera (zooplankton) Coral reefs

Coccolithophore

PteropodCorals

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Impacts of Ocean Acidification Deformed coccoliths

Experimental corrosion of calcium shells Pteropod (48 hrs) b = acid, c = normal seawater

Healthy, swimming pteropod

What will happen to the Deadliest Catch?

Coccolithophore bloom in the Bering Sea

Benthic organisms

Salmon

Marine Mammals

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How will ocean acidification impact marine foodwebs?

All organisms are linked to one another through a complex foodweb

Fish protein is an important component of the human diet

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Pterpods can compose up to 50% of the diet of juvenile salmon

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Will fish (and larvae) lose their way?

Use calcareous internal structures for:

Migration Otolith: key sensory structure Elevated CO2 results in larger,

misshapen structure

Settling Statolith: granules in statocyst used

to maintain equilibrium and orientation

Feeding Gastrolith: stone in stomach to aid in

digestion

Misshapen otolith

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Will whales go deaf? Absorption of sound in

seawater changes with the chemistry pH

Sound causes groups of atoms to vibrate, absorbing sounds at specific frequencies

More acidic the seawater, the less low- and mid-frequency sound it absorbs

Sounds below about 3,000 cycles per second travel further

Low frequency sounds used by marine mammals

CO2+ H2O + CO3-

2<==>2HCO3-1

Increasing carbon dioxide in the atmosphere leads to an increase in the acidity of seawater, which in turn allows sounds (such as whale calls) to travel farther underwater

What role does THC play?

Downwelling (cold) waters carry carbon dioxide deep into the ocean, taking it away from the atmosphere Deep and bottom water formation areas are sink for atmospheric CO2

Flux of CO2 from atmosphere into ocean

Upwelling waters bring deep water to the surface where it is in contact with the atmosphere Flux of CO2 from surface ocean to atmosphere

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Why are WA waters so acidic?

During the summer months: Ekman transport results in

divergence along coast Seasonal Upwelling

Deep water carried to surface High CO2 & nutrients

Low O2

Coastal waters enter PS

120m

Why are WA waters so acidic?

Clams (mussels, oysters) made out of ?

In-class Activity:

Q1: FULL NAME

Q2: Fill in the blanks

Old water is ______ and ______ rich, ______ poor

What’s happening to our local shellfish industry?

Watch: https://www.youtube.com/watch?v=

x7MpI9dZIjk

Understanding Ocean Acidification

Chemistry of oceans depends on chemistry of atmosphere

More CO2 in atmosphere = more CO2 in oceans

More CO2 in oceans = more acidic oceans (lower pH)

More acidic oceans = negative impact (growth, reproduction, survival) on algae and animals with shells or skeletons made of calcium carbonate

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Test your knowledge

Can you describe the role the oceans play in the global carbon cycle?

Can you identify the factors that determine how much O2 or CO2 dissolves in seawater?

Can you explain how increasing concentrations of CO2 in the atmosphere results in a change of ocean pH?

Can you explain how a change in ocean pH affects marine organisms?

Can you explain thermohaline circulation and how the oceans transport and dissolved gases (O2, CO2)?