EFFECTS OF ELEVATED TEMPERATURE ON A CORAL REEF FISH AND THE - - PowerPoint PPT Presentation

Jennifer M Donelson Philip L Munday Mark I McCormick

EFFECTS OF ELEVATED TEMPERATURE ON A CORAL REEF FISH AND THE POTENTIAL FOR ACCLIMATION

Global Warming in the Tropics

• Global temperatures are predicted to increase between

2-4°C by 2100

Lough 2007

• Temperatures will rise less in the tropics than temperate

regions

• Tropical sea surface

temperature is predicted to increase up to 3°C by 2100

Tropical Ectotherms

• Have narrower thermal

tolerances

• Living closer to their thermal
• ptimum and maximum
• Increase may be smaller but are

potentially more susceptible

• For tropical reef fish our

knowledge on thermal sensitivity is poor

Tewksbury et al 2008

Current temperature range Predicted mean temperature in 2100 Current mean temperature Predicted temperature range in 2100

Relative Darwinian fitness

Temperature (°C) 1.0 0.8 0.6 0.4 0.2 0.0 1.0 0.8 0.6 0.4 0.2 0.0

• 10 0 10 20 30 40

TROPICAL SPECIES HIGH-LATITUDE SPECIES

Temperature Fitness

Optimum Maximum

Response to a Changing Environment

Acclimation

– Modification of behavioral, physiological or morphological characteristics – Phenotypic plasticity and does not involve genetic change → limits to plastic responses – Modifications that are made to best suit an environment → not all responses may be beneficial Developmental = response within a generation generally during early ontogeny Transgenerational = parental effects to offspring phenotype

Potential Effects of Temperature

• Metabolic rate
• Physiological

condition

• Growth rate
• Reproduction
• Development

rate

• The effects of elevated

water temperature on tropical reef fish

• What is the potential for

developmental thermal acclimation

• What is the potential for

transgenerational thermal acclimation

Research Aims

Experimental Design

Location:

Central Great Barrier Reef

Study Species:

Spiny Chromis Acanthochromis polyacanthus

• Wide spread Indo-Pacific

reef fish

• Easily reared in captivity
• Mature in 2 years

Breeding temperature

Current + 1.5°C + 3.0°C Summer mean: 28.5°C 30.0°C 31.5°C

• Reproduction:
• Egg size
• # of eggs per clutch
• Offspring characteristics:
• Length
• Weight
• Yolk size

Experimental Design

n=7-8 pairs per temperature

With increasing temperature:

• Reduced number of

pairs that reproduced

• Reduced egg size
• Reduced fecundity
• No difference in timing
• f breeding

Reproduction

Donelson et al. 2010 MEPS 401:233-243

250 350 450 550 650 28.5 30.0 31.5

Clutch size Temperature (°C)

3.5 4 4.5 5 5.5

Egg area (mm2) 87% 38% 43%

Elevated temperature:

• Offspring are:
• shorter
• lighter
• less yolk
• Only 2 of 3 clutches in

31.5°C surviving till hatching

Offspring Attributes

4 4.4 4.8 28.5 30.0 31.5

Standard length (mm)

2.5 3 3.5 4 4.5 28.5 30.0 31.5

Weight (mg) Temperature (°C)

1 1.2 1.4 1.6 28.5 30.0 31.5

Yolk area (mm2) Temperature (°C)

8 breeding pairs kept at current temperatures Current day +1.5°C +3.0°C

Developmental Acclimation

Current day +1.5°C +3.0°C

Summer Maturity 2 years 28.5, 30.0 & 31.5°C

F0 F1

• Resting metabolic rate (RMR)→mg O2 kg-1 h-1
• Measures the fall in O2% for up to 30min
• Maximum metabolic rate (MMR)
• Swum at maximum capacity for

5-10 minutes

• Aerobic scope = MMR/RMR

Measuring Metabolic Rate

Metabolic rate Temperature

Resting Maximum Scope

Pörtner and Farrell Science 2008

Metabolic Rate and Aerobic Scope

Resting metabolic rate:

• Current day fish increase in

RMR

• No acclimation at +1.5°C
• Reduction in RMR +3.0°C

Aerobic scope:

• Decline in scope with

increasing temperature for current day

• Increase in scope in +3.0°C,

but not to level of current day at 28.5°C

1 1.5 2 2.5 3 28.5 30 31.5

Aerobic scope Testing temperature (oC)

current day +1.5°C +3.0°C

100 140 180 220 260 28.5 30 31.5

RMR (mg O2 kg-1 hr-1) Testing temperature (oC)

current day +1.5°C +3.0°C

100 140 180 220 260 28.5 30 31.5

RMR (mg O2 kg-1 hr-1) Testing temperature (oC)

current day +1.5°C +3.0°C

Donelson et al. 2011 GCB 17:1712-1719

Reproduction with Acclimation

100 150 200 250 300 350 400 current day +1.5°C +3.0°C

Clutch size Temperature treatment

3 3.5 4 4.5 current day +1.5°C +3.0°C

Egg area (mm2) Temperature treatment

With acclimation:

• Increased number of pairs

reproducing in +1.5°C

• Still less reproducing in

+3.0°C

• Reduced egg size only in

+3.0°C

• Increased fecundity in +1.5°C
• +3.0°C only reproduce during

start of summer

→ +1.5°C no acclimation in RMR,

but in reproduction

→ +3.0°C previously showed

thermal acclimation, but poorer reproduction

64% 54% 36%

Offspring Attributes

1.1 1.2 1.3 1.4 current day +1.5°C +3.0°C

Yolk area (mm2) Treatment temperature

3 3.2 3.4 3.6 3.8 4 4.2

Weight (mg)

With acclimation:

• Current day offspring

largest and heaviest

• Reduced size in +1.5°C

and +3.0°C

• No differences in yolk size

→ Since no difference in yolk +1.5 and +3.0°C have more provisioning proportionally

4.5 4.6 4.7 4.8 4.9 5 5.1 5.2 5.3 5.4

Standard length (mm)

Trangenerational Methods

8 breeding pairs kept at current temperatures Current day +1.5°C +3.0°C Current day +1.5°C +3.0°C +1.5°C +3.0°C Current day

+ 1.5°C + 3.0°C

No acclimation Developmental acclimation Trangenerational acclimation

Testing at 3 months post-hatching RMR, MMR and aerobic scope

F0 F1 F2

Transgenerational Acclimation

500 600 700 800 900 1000 28.5 30 31.5

RMR (mg O2 kg-1 hr-1) Testing temperature (°C)

no acclimation developmental acclimation transgenerational acclimation 1.5 2 2.5 3 3.5 28.5 30 31.5

Aerobic scope Testing temperature (°C)

Developmental acclimation:

• Only at +3.0°C RMR

Transgenerational acclimation:

• Both +1.5°C and +3.0°C

RMR and aerobic scope

→ Both developmental and

transgenerational similar reduction in +3.0°C

→ Transgenerational fish

have equaled current day fish values of some RMR and scope

• Current populations of tropical reef fish are

sensitive to relatively small increases in water temperature

• Limited ability to cope with warmer water

temperatures through developmental acclimation

• Transgenerational acclimation produces offspring

with metabolic performance equivalent to current day populations at current temperatures Future: → F2 offspring at maturity → Investigate acclimation in a range of fish species and different populations

Summary

Acknowledgements

• Australian Coral Reef Society

Student Award

• GBRMPA Science for

Management Awards

• CSIRO Climate Adaptation

Flagship Scholarship

• ARC Centre of Excellence for

Coral Reef Studies