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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
3
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
7
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
20
19
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 !