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LESSONS FROM CORAL REEF DEVASTATION, REORGANISATION, AND RECOVERY

Nick Graham@naj_graham

www.lec-reefs.org

Williams & Graham (2019) Func Ecol

Early reef species existed with the dinosaurs

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Uncertain futures in the Anthropocene

Williams & Graham (2019) Func Ecol

Coral Bleaching

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Gre

g T

ord

a

“Roughly half of the corals on the #GreatBarrierReefdied in the past 18 months (from global warming).”

Terry Hughes

BLEAK TIMES!

Fiji Japan

Maldives Seychelles

… and of course it wasn’t just the GBR

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Hughes et al. 2018 Science

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Graham et al. PLOS ONE 2008

Change in coral cover through 1998

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REEF TRAJECTORIES FOLLOWING MAJOR

BLEACHING

REGIMESHIFT(9 sites)

RECOVERY(12 sites)

Gra

ham

et

al. 2

015

Nat

ure

Recovery versus regime shifts

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REGIMESHIFT(9 sites)

RECOVERY(12 sites)

Gra

ham

et a

l. 2

015

Nat

ure

Recovery versus regime shifts

Robinson et al. 2019 Global Change Biol

Novel fish communities

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Wilson et al. 2019 Coral Reefs

Boom and bust of keystone structure

1994 2005 2008 2011 2014 2017

Mas

sive

co

ral

Bra

nch

ing

cora

l

Tot

al c

ora

l

Branching coral recovery post-1998

Bra

nch

ing

co

ral l

oss

in 2

01

6

Bleaching Bleaching

PREDICTORS OF RECOVERY

Gra

ha

m e

t al.

20

15

Na

ture

Rugosity

Juvenile coral density

Depth

Herbivore biomass

Nutrients

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Hughes et al. 2010 TREE MacNeil et al. 2015 Nature

Nutrient pollution and fishing are pervasive

NUTRIENTS

10

Ma

cNe

il e

t al.

Na

ture

Eco

Evo

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Coral cover dynamics on the GBR

MacNeil et al. Nature Eco Evo 2019

Acropora cover dynamics on the GBR

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MacNeil et al. in review

Water quality mediates coral recovery on the GBR

17% improvement in catchment water quality would enable many reefs to recover between bleaching events to 2050

D’Angelo & Wiedenmann 2014 Curr Opin Env Sust

High nitrogen, low phosphorus

High nitrogen AND phosphorus

Slower growth Bleaches easier

Faster growth Bleaches at higher threshold

Not all nutrients are bad

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Fox et al. Curr Biol 2018

Corals feed more in naturally nutrient rich waters

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INVASIVE RATS

Seabirds bring nutrients from open ocean

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Graham et al. 2018 Nature

Seabirds & nutrients higher on rat-free islands

Graham et al. 2018 Nature

Huge nutrient subsidy

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Graham et al. 2018 Nature

Huge nutrient subsidy

Fish aged and growth assessed using otoliths

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Graham et al. 2018 Nature

Fish grow faster with seabird nutrient subsidies

UNDERWATER SURVEYS OF FISH COMMUNITIES AT EACH ISLAND

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Gra

ha

m e

t al.

20

18

Na

ture

Fish biomass higher with seabird nutrient subsidy

Gra

ha

m e

t al.

20

18

Na

ture

47% higher total fish biomass

Fish biomass higher with seabird nutrient subsidy

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CORAL BLEACHINGCoral bleaching

Benkwitt, Wilson & Graham GCB (2019)

Shifts to calcifying algae next to seabird islands

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Savage 2009 Sci Reports

Seabird nutrient enhance coral growth FOUR times !!

FISHING

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Robinson et al. Nature Eco Evo (2019)

Jam

es R

obin

son

Fisheries following coral lossC

PU

E

Ecology alone is far from enough

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Kittinger et al. 2012 Ecology & Society

Marrying social and ecological systems

Hicks et al. 2016 Frontiers Ecol & Environ

Underlying social drivers of change

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McClanahan et al. 2015 Cons Bio

Gear-based management

More gears restricted Protected areas

Implications for algal dominated systems, biodiversity, and changing fisheries compositions

Reducing terrestrial nutrient pollution will be essential for some reef systems to recover

Not all nutrients are bad, and natural flows should be re-instatedDiverse approaches to ecosystem-based fisheries management

should be explored

CORAL REEFS ARE CHANGING

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Thank You !