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

EFFECTS OF ELEVATED TEMPERATURE ON A CORAL REEF FISH AND THE POTENTIAL FOR ACCLIMATION Jennifer M Donelson Philip L Munday Mark I McCormick

Global Warming in the Tropics • Global temperatures are predicted to increase between 2-4°C by 2100 • Temperatures will rise less in the tropics than temperate regions • Tropical sea surface temperature is predicted to increase up to 3°C by 2100 Lough 2007

Tropical Ectotherms Tewksbury et al 2008 TROPICAL SPECIES 1.0 Fitness Optimum 0.8 0.6 Maximum 0.4 Relative Darwinian fitness Temperature 0.2 • Have narrower thermal 0.0 tolerances HIGH-LATITUDE SPECIES 1.0 • Living closer to their thermal 0.8 optimum and maximum 0.6 0.4 • Increase may be smaller but are 0.2 potentially more susceptible 0.0 -10 0 10 20 30 40 • For tropical reef fish our Temperature (°C) knowledge on thermal sensitivity Current temperature range Predicted temperature range in 2100 is poor Current mean temperature Predicted mean temperature in 2100

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

Research Aims • 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

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

Experimental Design Breeding Current + 1.5°C + 3.0°C temperature Summer mean: 28.5°C 30.0°C 31.5°C n=7-8 pairs per temperature • Reproduction: - Egg size - # of eggs per clutch • Offspring characteristics: - Length - Weight - Yolk size

Reproduction 5.5 With increasing 87% temperature: 5 Egg area (mm 2 ) 38% 4.5 • Reduced number of 43% pairs that reproduced 4 3.5 • Reduced egg size 650 • Reduced fecundity 550 Clutch size • No difference in timing 450 of breeding 350 250 Donelson et al. 2010 MEPS 28.5 30.0 31.5 401:233-243 Temperature (°C)

Offspring Attributes Elevated temperature: • Offspring are: Standard length (mm) 4.8 - shorter - lighter 4.4 - less yolk • Only 2 of 3 clutches in 4 31.5°C surviving till hatching 28.5 30.0 31.5 4.5 1.6 Yolk area (mm 2 ) 4 Weight (mg) 1.4 3.5 1.2 3 2.5 1 28.5 30.0 31.5 28.5 30.0 31.5 Temperature (°C) Temperature (°C)

Developmental Acclimation F0 8 breeding pairs kept at current temperatures Current day +1.5°C +3.0°C F1 +3.0°C +1.5°C Current day Summer Maturity 2 years 28.5, 30.0 & 31.5°C

Measuring Metabolic Rate • Resting metabolic rate (RMR) → mg O 2 kg -1 h -1 • Measures the fall in O 2 % for up to 30min • Maximum metabolic rate (MMR) • Swum at maximum capacity for 5-10 minutes • Aerobic scope = MMR/RMR Pörtner and Farrell Science 2008 Maximum Metabolic rate Scope Resting Temperature

Metabolic Rate and Aerobic Scope Donelson et al. 2011 GCB 17:1712-1719 RMR (mg O 2 kg -1 hr -1 ) RMR (mg O 2 kg -1 hr -1 ) Resting metabolic rate: current day current day 260 260 +1.5°C +1.5°C • Current day fish increase in +3.0°C +3.0°C 220 220 RMR 180 180 • No acclimation at +1.5°C 140 140 • Reduction in RMR +3.0°C 100 100 28.5 30 31.5 28.5 30 31.5 Testing temperature ( o C) Testing temperature ( o C) Aerobic scope: 3 current day +1.5°C • Decline in scope with 2.5 +3.0°C Aerobic scope increasing temperature for 2 current day 1.5 • Increase in scope in +3.0°C, but not to level of current day 1 at 28.5°C 28.5 30 31.5 Testing temperature ( o C)

Reproduction with Acclimation With acclimation: 64% • Increased number of pairs 54% 4.5 Egg area (mm 2 ) reproducing in +1.5°C 4 36% • Still less reproducing in +3.0°C 3.5 • Reduced egg size only in 3 +3.0°C current day +1.5°C +3.0°C • Increased fecundity in +1.5°C Temperature treatment • +3.0°C only reproduce during 400 start of summer 350 Clutch size 300 → +1.5°C no acclimation in RMR, 250 but in reproduction 200 → +3.0°C previously showed 150 100 thermal acclimation, but poorer current day +1.5°C +3.0°C reproduction Temperature treatment

Standard length (mm) 5.4 Offspring Attributes 5.3 5.2 5.1 5 4.9 With acclimation: 4.8 4.7 • Current day offspring 4.6 4.5 largest and heaviest 4.2 4 • Reduced size in +1.5°C Weight (mg) 3.8 and +3.0°C 3.6 3.4 • No differences in yolk size 3.2 3 1.4 → Since no difference in yolk Yolk area (mm 2 ) 1.3 +1.5 and +3.0°C have more provisioning proportionally 1.2 1.1 current day +1.5°C +3.0°C Treatment temperature

Trangenerational Methods 8 breeding pairs kept at current temperatures F0 Current day +1.5°C +3.0°C F1 Current day F2 Current day +1.5°C +3.0°C +1.5°C +3.0°C No acclimation Testing at 3 months post-hatching + 1.5°C + 3.0°C RMR, MMR and aerobic scope Developmental acclimation Trangenerational acclimation

Transgenerational Acclimation no acclimation 1000 Developmental acclimation: RMR (mg O 2 kg -1 hr -1 ) developmental 900 • Only at +3.0°C RMR acclimation transgenerational 800 acclimation Transgenerational 700 acclimation: 600 • Both +1.5°C and +3.0°C 500 RMR and aerobic scope 28.5 30 31.5 Testing temperature (°C) → Both developmental and 3.5 transgenerational similar reduction in +3.0°C 3 Aerobic scope → Transgenerational fish 2.5 have equaled current day 2 fish values of some RMR and scope 1.5 28.5 30 31.5 Testing temperature (°C)

Summary • 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

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