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Announcements:
Final exam: Tuesday, March 17, 8:00 ‐10:00 on CanvasGet to a site with ensured network connectivity!This is YOUR responsibility!
Let me know if you have issues with this.
Marine Ecology Field Lab this summer:First session: MW 9‐12:30 in CBB 115.Instructor: Josh Smith ([email protected])
TODAY
Lecture:
1. Environmental change – Ocean Acidification‐ how does OA happen?‐ where does it occur?
2. Physiology, behavior, & movement
3. Ecology‐ how do we study this?‐ effects on post‐settlement processes‐ effects on pre‐settlement processes
TODAY
Multiple effects of increased CO2
1. Warming • Stratification• Sea‐level rise• Storms• Deoxygenation
2. Acidification
Harley et al. 2006
Multiple effects of increased CO2
Ocean AcidificationThe historical perspective
• CO2 in the atmosphere has risen from 280 ppm in 1800 to about 380 ppm today—a 36% rise.
• Oceans may have absorbed about one‐half of this CO2; about one‐third of currently produced CO2 goes into the oceans.
• Average oceanic pH has fallen from ~8.16 to ~8.05during this 200 year period.
• Projected rates of decrease in pH are model‐dependent. But, even conservative models say a pH of 7.9 could occur by the end of this century.
Trends of atmospheric CO2 and ocean CO2 and pH
CO2
CO2(aq)+ H2O
CO2
CO2(aq)+ H2O H2CO3 HCO3‐ + H+
Carbonic acid Bicarbonate
CO2
CO2(aq)+ H2O H2CO3 HCO3‐ + H+
pH
Carbonic acid Bicarbonate
CO2
CO2(aq)+ H2O H2CO3 HCO3‐ + H+
CaCO3 CO32‐ + Ca2+
Carbonic acid Bicarbonate
Calcium carbonate Carbonate Calcium
CO2
CO2(aq)+ H2O H2CO3 HCO3‐ + H+
CO32‐ + H+
CaCO3 CO32‐ + Ca2+
Carbonic acid Bicarbonate
Calcium carbonate Carbonate Calcium
pH = 10
pH = 4 pH = 6
CO2
CO2(aq)+ H2O H2CO3 HCO3‐ + H+
CO32‐ + H+
CaCO3 CO32‐ + Ca2+
HCO3‐
Carbonic acid Bicarbonate
Calcium carbonate Carbonate Calcium
Bicarbonate
pH = 4 pH = 6
pH = 6
pH = 10
CO2
CO2(aq)+ H2O H2CO3 HCO3‐ + H+
HCO3‐ CO3
2‐ + H+
CaCO3 CO32‐ + Ca2+
Carbonic acid Bicarbonate
Calcium carbonate Carbonate Calcium
Bicarbonate
pH = 4 pH = 6
pH = 6
pH = 10
Ocean acidification ‐ Projections
CC SM3‐modeled decadal mean pH at the sea surface
8.4
8.2
8.0
7.8
7.6
pHT
Feely et al. 2009
1875 1995
20952050
1
14
12
13
11
10
9
8
7
6
5
4
3
2
0
Neutral
Moreacidic
Morealkaline
Lemon juice
Seawater (8.1‐8.2)
Milk of magnesia
Vinegar
The pH scale
pH = ‐ log [H+]
1
14
12
13
11
10
9
8
7
6
5
4
3
2
0
Neutral
Moreacidic
Morealkaline
Lemon juice
Seawater (8.1‐8.2)
Milk of magnesia
Vinegar
H+ (moles/liter)1
0.01
0.0001
0.000001
0.00000001
0.000000000001
0.00000000000001
Predicted changes in pH state are not homogenous.
Tropical oceans are predicted to see the largest absolutedecrease.
Polar regions are expected to see the largest relative decrease.
Ocean acidificationProjections
Spatial patterns in absolute decrease in pH
Spatial patterns in percent decrease in pH
Pattern: Global models don’t predict the conditions organisms may experience
Recent monitoring revealed very low pH water (<7.8) associated with upwelling
Organisms may experience much more extreme and variable environments
Distribution of the depths of the undersaturated water (aragonite saturation < 1.0; pH < 7.75)
Aragonite saturation state is commonly used to track ocean acidification because it is a measure of carbonate ion concentration.
When aragonite saturation state falls below 3, these organisms become stressed.
When saturation state is less than 1, shells and other aragonite structures begin to dissolve.
Upwelling of very low pH waters on continental shelf
Feely et al. 2008 Science
Lecture:
1. Environmental change – Ocean Acidification‐ how does OA happen?‐ where does it occur?
2. Physiology, behavior, & movement
3. Ecology‐ how do we study this?‐ effects on post‐settlement processes‐ effects on pre‐settlement processes
TODAY
Physiology, behavior, & morphology
II. Ocean acidification
A. Calcification and dissolution
B. Bioenergetics
C. Photosynthesis
D. Behavior
Figure: Kleypas and Yates 2009
Data: Langdon et al. 2003
Experimental CO2 enrichment:Coral calcification decreases with increasing acidification
Acidification
Calcification and dissolution
Bioenergetics
OA changes the ‘cost of living’?
GrowthCost of Living
Reproduction
Normal
Reproduction
GrowthCost of Living
Stressed
EnergyBudget
Energy budgets – If the cost of living (e.g. calcification) increases,less energy is available for growth and reproduction.
Mytilus edulisPhoto: Seattle Aquarium
pCO2 ppmv
Net calcification
Gazeau et al. 2007
windwindwind
(Melzner et al. 2011)
Upwelling in fjords enriches surface waters with CO2
Pattern: Kiel Bay: a seasonally CO2 enriched habitat
Slide adapted from F. Melzner
Dominated by calcifying species!Blue mussel‐Mytilus edulis
Barnacle – Amphibalanus improvisusEchinoderm – Asterias rubens
more acidic
Highest recruitment
of invertebrate
species occurred at peak pCO2
pCO2 >100 Pa(>1000 µatm)
Thomsen et al.2010Biogeosciences
pCO2 >230 Pa(> 2300 µatm)
Pattern: dominance of calcifying macrobenthos
Slide adapted from F. Melzner
Seasonal variation in pCO2
Hypothesis: Increased food supply can buffer effects of acidification
Melzner et al. 2011
Low food
High food
The effects of OA will depend on food
availability
and other factors
PhotosynthesisPlants and algae use CO2!
Scent + Normal pH
Scent + Reduced pH
Munday et al. 2009 PNAS
Behavior
Pattern: Many reef fish use olfactory cues to locate suitable settlement habitat.
General hypothesis: OA might affect their ability to detect the olfactory cues
Control Unsuitable habitat
Suitable habitat
Unreliablecue
Suitable habitat
Results: Juvenile fish lost their “homing ability” – or their ability to find suitable habitat
Behavior
However: recent study has refuted these results
Lecture:
1. Environmental change – Ocean Acidification‐ how does OA happen?‐ where does it occur?
2. Physiology, behavior, & movement
3. Ecology‐ how do we study this?‐ effects on post‐settlement processes‐ effects on pre‐settlement processes
TODAY
Harley et al. 2006
3. Ecology
Post‐settlement processes
A. OA and competition
Pattern: At volcanic CO2 vents, calcifying algae are less abundant in more acidic conditions, where fleshy turf algae dominate.
No CO2 vents CO2 vents
Kroeker et al. 2012
OA and competition ‐ Kroeker et al. 2012
General hypothesis: Fleshy algae is outcompeting calcifying algae for space by overgrowing it.
Specific hypothesis: In areas of CO2 venting, crustose coralline algae will successfully recruit onto settlement tiles during early stages of succession but will be overgrown by turfy algae during the late stages of succession.
Test: Settlement tiles in 3 pH zones for 1.5 years
OA and competition ‐ Kroeker et al. 2012
Hall‐Spencer et al. 2008
Castello, Ischia, Italy
Extreme Low
Seawater pH
LowAmbient
Calcified taxaResults: Calcified taxa overgrown by fleshy algae in low pH
Turf algae
0
0.2
0.4
0.6
0.8
-1 4 9 14
0
0.2
0.4
0.6
0.8
0 2 4 6 8 10 12 14
Months
80
60
40
20
80
60
40
20
Ambient
Low
Extreme low
OA and competition ‐ Kroeker et al. 2012
0
20
40
60
80
current future0
20
40
60
80
current future
0
1
2
3
current future0
2
4
6
current future
0
10
20
30
current future0
10
20
30
current future
Turf algae
Pe
rcen
t cover
Turf algae
Growth (m
g/da
y)
Levels of CO2
Vents
Mesocosms
Lab experiments
Connell, Kroeker, et al. 2013 P Roy Soc B
Temperate TropicalOA and competition ‐ Kroeker et al. 2012
Lecture:
1. Environmental change – Ocean Acidification‐ how does OA happen?‐ where does it occur?
2. Physiology, behavior, & movement
3. Ecology‐ how do we study this?‐ effects on post‐settlement processes‐ effects on pre‐settlement processes
TODAY
Pre‐settlement processes
OA decreases larval survival + development
pH 8.1
pH 7.7
Ophiothrix fragilis
OA slows (skeletal) development
Pre‐settlement processes
Ocean acidification and settlementDoropoulos et al. 2012
Acropora millepora
Newly settled larva
Planulalarva
Pattern: Many corals use coralline algae for settlement. Research suggests OA will decrease percent cover of coralline algae
Pre‐settlement processes
Ocean acidification and settlement
General hypothesis: OA will affect coral recruitment through changes in benthic community composition.
Specific hypothesis 1: Settlement tiles cultured in high CO2 seawater will have a different community than those cultured in low CO2, and coral recruitment will be linked to crustose coralline algae cover.
Methods: “Cultured” settlement tiles on reef for 6 months, then in lab in high, medium or low CO2for 2 months.
Test 1: Settlement assay on tiles raised in low, medium, and high CO2 in ambient (control) seawater.
Doropoulos et al. 2012
OA and settlement ‐ Doropoulos et al. 2012
Coral settle
men
t
low med high
pCO2
Results 1: Fewer coral larvae settled on tiles cultured in medium CO2.
Coral larvaeSettlement tiles
Exposed to high CO2
Test 1 Yes No
No Yes
Yes No
Pre‐settlement processes
Ocean acidification and settlementDoropoulos et al. 2012
General hypothesis: OA will affect coral recruitment through changes in larval settlement behavior
Specific hypothesis 2: larvae exposed to normal benthic communities in seawater of different CO2 levels will differ in their settlement rates
Methods: Exposed larvae to normal (ambient) benthic communities in waters of three different CO2 levels
Test 2: Settlement assay in low, medium, and high CO2 water.
OA and settlement ‐ Doropoulos et al. 2012
Coral larvaeSettlement tiles
Exposed to high CO2
Yes No
No Yes
Yes No
Test 2
Results 2: Fewer coral larvae settled on tiles in higher CO2 water.
Coral settle
men
t
Pre‐settlement processes
Ocean acidification and settlementDoropoulos et al. 2012
General hypothesis: OA will affect coral recruitment through changes in larval settlement behavior
Specific hypothesis 3: larvae exposed to benthic communities cultured different levels of CO2 ANDexposed to seawater of different CO2 levels will differ in their settlement rates
Methods: Exposed larvae to benthic communities cultured at different levels of CO2 AND water of different levels of CO2.
Test 3: Settlement assays…
A. OA and settlement ‐ Doropoulos et al. 2012
Coral larvaeSettlement tiles
Exposed to high CO2
Yes No
No Yes
Yes YesTest 3
Results 3: Fewer coral larvae settled on tiles cultured at higher CO2and higher CO2 water.
Coral settle
men
t
OA and settlement ‐ Doropoulos et al. 2012
Results of all three experiments
Coral larvaeSettlement tiles
Exposed to high CO2
Yes No
No Yes
Yes Yes
Test 1
Test 2
Test 3
low med highpCO2
Coral settle
men
t
OA and settlement ‐ Doropoulos et al. 2012
Conclusions: Ocean acidification could affect settlement through both mechanisms…or it could affect the cues themselves?
Coral settle
men
t
low med highpCO2
Announcements:
Final exam: Tuesday, March 17, 8:00 ‐10:00 on CanvasGet to a site with ensured network connectivity!This is YOUR responsibility!
Let me know if you have issues with this.
Marine Ecology Field Lab this summer:First session: MW 9‐12:30 in CBB 115.Instructor: Josh Smith ([email protected])
Thank you! Have a nice break
TODAY