L14 Ocean Acidification

Question 1

What is OA>

Answer 1

reduction in ocean pH due to uptake of anthropogenic CO2.

Question 2

What are ocean CO” levels now and how do they fluctuate?

Answer 2

Time series has a long record of ocean pH and CO2 conc, now the CO2 levels areat approx 400ppm -30% higher than any time in the past 650,000 years. CO2 levels fluctuate intensively during glacial cycles but speed of increase since industrial revolution is unprecedented.

Question 3

what is the IPCC and what do they suggest?

Answer 3

Intergovernmental panel on climate change
suggests CO2 will continue to rise and lower pH of oceans. leads to loss of accessible carbonate (aragonate and calcite).

Question 4

Where does ocean acidification affect the most?

Answer 4

Low levels of saturated CaCO3 present at poles, so effects of OA is most substantial to calcifying organisms at the poles.

Question 5

How does OA affect calcifying organisms?

Answer 5

Atmospheric CO2 absorbed by water and reacts with water to give basic bicarbonate ions HCO3- and acidic H+.
To make shells, calcifying organisms require CO3 for the reaction: Ca2+ + CO3(2-) = CaCO3.
However, the H+ released from acidification in water reacts with the CO3(2-), to give HCO3-, so the CO3(2-) is not available for calcification.

Question 6

How does OA affect existing shells?

Answer 6

free H+ can react with CaCO2 existing shells, to result in dissolution of the structures.
Affects corals, urchins, fronds in coralline algae, fish otoliths, pteropods.

Question 7

How does ocean acidification affect specific organisms

Answer 7

• causes thinner, smaller, weaker shells in shellfish, esp larval stages
• this increased risk of dessiccation and vulnerability to crushing and drilling by predators, and wave action.
• deformation of flagellae of corals causes reduced fertilisation success, potential effects on recruitment success.
• reduced predator avoidance in juvenile clownfish due to impaired hearing. deformed morphology of otoliths or a disruption of acid/base balance in the neuro sensory system. reduced fitness.
• Pteropods in Southern ocean, natural environment study. Sites with aragonite levels <100% so potential de-calcification of organisms. Evidence of shell dissolution at these sites, but not at higher aragonite concentrations.

Question 8

What species show that experience may affect sensitivity to pH?

Answer 8

Could predict copepod larval population effects.
eg Calanus is migratory, experience vertical migrations daily with high ph changes.
Oithona - non migratory and much less able to cope when challenged with pH changes.
Shows greater impact of OA on non migratory zoo plankton. Maybe increased energetic costs of maintaining physiological processes under higher pH.

Question 9

What effects might OA have on non calcifying organisms?

Answer 9

Studies of CO2 vents in the med sea - water closer to vents is higher in pH, fundementally changes structure of species assemblages.
Closer to vents: less calcaerous algae, more non calcaerous algae, fewer urchins, limpets and barnacles. Clear shell dissolution.

Question 10

Why are tropical oceans more vulnerable to OA?

Answer 10

Keystone species are vulnerable in coral reefs, eg coral. Predictions are: Corals become increasingly rare, algae becomes more abundant, biodiversity declines.

Question 11

What are implications for harvested resources

Answer 11

pink salmon breeds in rivers but is fished at sea where 45% of diet is pteropods. so decline of salmon could be due to OA. reduced salmon boy size and weight.

Question 12

describe some community level exeriments

Answer 12

conducted on miniature reef mesocosms.

acidification led to reduced coral abundance and increased macro algal abundance.

Question 13

What are 4 options for organisms vulnerable to OA?

Answer 13

Tolerate
Adapt
Move
go extinct

Question 14

Example of how animals can tolerate OA

Answer 14

Possible that animals raised in high CO2 ocean wont show much difference. eg sea urchin shows no difference in egg fertilisation success of differing acidities. Perhaps jelly coating of egg may protect life cycle stages but could also be a cost if it must produce more coating to succeed.

Question 15

What is required for species to adapt to OA

Answer 15

Requires a shot gen time. long lived species are likely not to adapt.
Requires selection to act on either a new mutation or standing genetic variation.

Question 16

why is it not likely for species to move?

Answer 16

Less likely for benthic/demersal species or with dependence on key resources in a particular location. Less likely to sense changes in pH directly, mvt would only be triggered by response to changing resource availability.

Question 17

where is it more likely for species to adapt to OA

Answer 17

in places where there is a naturally high range of pH values eg upwelling zone off N california.

Question 18

Example of a species known to adapt to OA

Answer 18

Coccolithophore - Emilinaria huxleyi
Fast reproducing species, reared for 500 generations in an experiment with 4 CO2 scenarios. Measures the growth rate and particlate inorganic carbon. Better performance of those allowed to evolve.

Question 19

How can society prevent OA?

Answer 19

Major - reduce ff emmissions
act locally to reduce C footprint.
Reduce run off from land - riparian buffers, wetlands
Conserve natural ph buffering of coastal soils
Return old crushed shells to sea.
Need to devlop techniques for monitoring. network of sensors needed as pH dynamics vary spatially and temporally.