Climate change impacts on reef algae

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Climate change impacts on reef algae

• Guillermo Diaz-Pulido
• Centre for Marine Studies
• ARC Centre of Excellence for Coral Reef Studies,
• The University of Queensland, Australia
• g.diazpulido_at_uq.edu.au
• Universidad del Magdalena, Colombia

All photos by G. Diaz-Pulido (unless noted)
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Outline

• Background
• Climate change factors
• Impacts of Warming
• Impacts of CO2 Ocean acidification
• Macroalgae
• Coral-algal interactions
• General Conclusions

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Background

• Key ecological roles
• Roles in reef degradation phase shifts

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Warming-induced coral bleaching and algal
increase
GBRMPA
Warming causes coral bleaching. Widespread
colonization after coral mortality
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Warming-induced coral bleaching and algal
increase
Benthic Algae
Corals
Diaz-Pulido McCook, 2002
Diaz-Pulido McCook 2002
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Increased coral bleaching
Frequency
Diaz-Pulido McCook, 2002
Hoegh-Guldberg, 1999

• Coral bleaching ? ? frequency intensity

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Warming-induced coral bleaching and algal
increase
?
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Coral reefs ecosystems and climate change
Climate change

• Anthropogenic climate change
• Caused increase in CO2 levels
• Emissions from fossil fuels
• Emissions from aerosols
• Cement manufacture
• Deforestation

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(No Transcript)
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CO2 levels
Geological eviden 20 mya
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CO2 levels
Lough, 2009
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CO2 levels IPCC
Yr 2100 900 ppm
Meehl et al. 2007, IPCC
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CO2 levels Recent models
Year 2100 gt1000ppm
Meinshausen et al. 2009. Nature, 458 1158-1162,
30 Apr
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Global warming IPCC

• Due to ? greenhouse gas

Yr 2100 4oC
To ? 0.74 oC last century
Meehl et al. 2007, IPCC
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Global warming Recent models
Yr 2100 5-7 oC
Year 2100 up 5-7 oC
Meinshausen et al. 2009. Nature, 458 1158-1162
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Climate change

• Increase CO2 temperatures will cause

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Storms
Oouchi et al 2006
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2007
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Vulnerability of macroalgae to climate change
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Vulnerability of macroalgae to climate change
CO2
ToC
Diaz-Pulido et al, 2007. GBRMPA
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Effects of Increased Temperature on Macroalgae
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Temperature

• Effects
• ? photosynthesis
• ? growth
• Wide range of tolerance
• 8 to 35oC (Pakker et al 1995)
• Many unable to survive gt33oC

Pakker et al 1995, J. Phycol 31 499-527
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Temperature

• Effects
• ? photosynthesis
• ? growth
• Wide range of tolerance
• 8 to 35oC (Pakker et al 1995)
• Many unable to survive gt33oC
• Narrow physiological thresholds

Pakker et al 1995, J. Phycol 31 499-527
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Temperature
Great Barrier Reef

• Effects
• ? photosynthesis
• ? growth
• Wide range of tolerance
• 8 to 35oC (Pakker et al 1995)
• Many unable to survive gt33oC
• Narrow physiological thresholds

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Effects of warming on seaweed photosynthesis
Thresholds
Halimeda opuntia

• Variable thresholds
• Can be narrow in many tropical algae

Temperature (oC)
Diaz-Pulido et al in prep.
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Temperature

• Effects
• ? photosynthesis
• ? growth
• Wide range of tolerance
• 8 to 35oC (Pakker et al 1995)
• Many unable to survive gt33oC
• Narrow physiological thresholds
• Distribution ranges
• Alter seasonality

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Temperature

• Effects
• ? photosynthesis
• ? growth
• Wide range of tolerance
• 8 to 35oC (Pakker et al 1995)
• Many unable to survive gt33oC
• Narrow physiological thresholds
• Changes in seasonality distribution ranges
• ? temperature ? ? Cover algal growth
• Small To ?? ? seasonality

D. Cuesta 2009
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Effects of warming on macroalgae

• Key knowledge gaps
• Adaptive capacity to cope with increased SST
• Identify vulnerable species to global warming
• Changes in latitudinal distributions
• Effects of ? temperature on temperature-controlled
  life cycles (not understood)
• Shifts in competitive ability (e.g. turfs more
  competitive than fleshy algae)

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Effects of Increased CO2 on Macroalgae
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Increased CO2 Ocean acidification
?CO2 ? ? Carbonic Acid ? ?pH Ocean
acidification
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H2CO3
Hoegh-Guldberg et al. 2007. Science 3181737-1742
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Increased CO2 Ocean acidification
Meehl et al. 2007, IPCC
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Impacts of increased CO2 on fleshy seaweeds
Gracilaria
1200 ppm

• Effects on fleshy algae
• ? photosynthesis
• ? growth, eg algae with no CCM

650 ppm
Control
Days
Gao et al., 1993. J. Appl. Phycol. 5563

• Very limited data for tropical species

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Impacts of increased CO2 on fleshy seaweeds
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Primary Productivity Respirometry
Respirometry chambers
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Impacts of increased CO2 on fleshy seaweeds
Photosynthesis
Macroalgae

• Small responses of algae to increased CO2
• Large variability in photosynthetic responses
  between taxa
• Minor to no apparent response (2 taxa)
• Bell shape response ? in medium, but ? in high
  CO2 (4 species)
• Increased with increasing CO2 (2 spp)
• Decreased with increasing CO2 (1 spp)

Diaz-Pulido et al in prep.
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Impacts of increased CO2 on calcareous algae
Aragonite saturation

• Reduced saturation state of aragonite and calcite
• Effects
• ? calcification of red coralline algae
• ? Primary production
• ? Recruitment
• ? mortality, dissolution

ppm CO2
Hoegh-Guldberg et al. 2007. Science 3181737-1742
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or CCA
Hoegh-Guldberg et al. 2007. Science 3181737-1742
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Impacts of increased CO2 on coralline algae
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Impacts of increased CO2 on calcareous algae
Porolithon onkodes
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Temperature
3
Low (25 oC)
High (28 oC)
2
1
Weight increase / month
0
n15
-1
To exacerbates CO2 impacts
-2
-3
Control
Medium
High
CO2
Anthony, Kline, Diaz-Pulido. 2008. PNAS
10617442-17446
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Net Productivity (umol O2 / cm2 / d) Porolithon
onkodes
Temperature
Low (25 oC)
High (28 oC)
Control
Medium
High
CO2
Anthony, Kline, Diaz-Pulido. 2008. PNAS
10617442-17446
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CO2-dosing and temperature control experiment
Control
2050
2090
Saturation state of High-Magnesium calcite lt1
Under saturated
Carbon parameters were estimated using the
program CO2SYS. The saturation state of calcite
assume a concentration of 14 Mole MgCO3
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Impacts of increased CO2 on calcareous algae
Kuffner et al 2007
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Impacts of increased CO2 on calcareous algae
Ambient CO2
High CO2

• Reduced saturation state of aragonite and calcite
• Effects
• ? calcification of red coralline algae
• ? Primary production
• ? Recruitment
• ? mortality, dissolution

• Shifts in spp. dominance
• Calcifying ? non-calcifying algae
• Loss of corallines ? settlement cues for coral
  larvae

Kuffner et al. 2008. Nature Geoscience
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Impacts of increased CO2 Shifts in dominance
Hall-Spencer et al. 2008. Nature 45496-99
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Impacts of increased CO2 Shifts in dominance
Shore
Volcanic CO2 vents
Hall-Spencer et al. 2008. Nature 45496-99
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Impacts of increased CO2 Shifts in dominance
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Effects of increased CO2 on fleshy calcareous
algae

• Key knowledge gaps
• Adaptive capacity to cope with ? CO2 and ? pH
• Potential adaptation by secreting less soluble
  skeletons
• CCA radiated during Eocene? World was warmer and
  had higher CO2 ? Adaptation?
• Identify vulnerable species, related to CCM
• Effects on reproduction, competitive ability (eg
  CCA ? fleshy algae)
• Decline in CCA and follow on effects on coral
  recruitment

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Coral Algal Interactions
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Coral-algal competition Ocean acidification

• Coral-algal competition is a critical process in
  reef ecology
• No information on the effects of ? CO2 on coral
  algal interactions

• Current experiments in the Great Barrier Reef

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Coral algal competition Ocean acidification

• Key knowledge gaps
• Explore variability in competitive outcomes
• Vulnerable coral Algal spp.
• Mechanisms of competition
• Chemical
• Microbial, etc
• Interactive effects of temperature CO2
• Roles of herbivory nutrients on interactions
  under high CO2

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Conclusions

• High diversity of taxa groups ? large
  variability in responses
• Variety of ecological roles ? impacts on reefs
  would be variable
• Effects on reef primary productivity
• Reef construction, sediment production
• Critical effects on coral settlement
• Will algae be the winners?
• Reef macroalgae are at least as vulnerable to
  ocean acidification and global warming as are
  corals
• Future reefs might not be dominated by fleshy
  seaweeds
• Winners (? red algae) losers (coralline algae)

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