1. Vulnerability of coral reefs
Janice Lough

2. Moving reefs out of comfort zone
Hoegh-Guldberg et al 2007

3. Outline Coral Reefs key coastal ecosystem many different reef types
narrow environmental limits
already shown impacts, e.g. bleaching
combined effects of disturbances
less time to recover
simpler reefs
healthy reefs will cope better

4. Many different types of reefs
13/22 PICTS have more reef than land area (e.g. ~Fiji 40%)
dominant coastal habitat
majority are oceanic
great diversity of reef types

5. With different levels of human use
support local fisheries
differences in local pressures

6. Location matters fringing continental reefs affected by river runoff
isolated oceanic reefs not well connected e.g. larval supplies
tropical cyclones> 10o from equator
El Niño/La Niña impacts

7. Important environmental factors
warm water temperatures
shallow well-lit waters
low sediment and nutrients
right ocean chemistry Ω >3.3
warmest parts of oceans
narrow temperature range

8. Corals must build skeletons fast enough to withstand natural forces of erosion
waves
tropical cyclones
sunshine
predators
coral eaters

9. A special relationship
symbiosis at heart of tropical coral reefs
photosynthetic algae live within coral animal
corals get enough energy for rapid calcification
form structurally complex reefs
home to thousands of other plants and animals

10. Relationship breaks down due to stress
stressed corals lose algae (and their pigments)
coral bleaching
seen more frequently due to warmer temperatures
corals living only ~1-2oC below upper thermal limit
too much fresh water also causes bleaching
Healthy - unbleached
Stressed - bleached
Recently dead

11. Ocean acidification 30% extra CO2 entered oceans
otherwise greater warming!
BUT changes ocean chemistry
harder to form skeletons & shells
more erosion

12. Ocean acidification: natural laboratory
high CO2 volcanic seeps, PNG
“winners” = massive corals
“losers” = branching, tabulate corals
reduced coral diversity
much simpler reef with lower pH
Normal pH = now
Mid pH = 2050
Lower pH = 2100
Fabricius et al 2011

13. Warmer temperatures very high vulnerability
already seen bleaching, diseases

14. More acidic ocean
high vulnerability
weaken reef framework

15. Stronger storms and heavier rainfall
moderate vulnerability
more disturbances = less time to recover

16. Higher sea level
some corals may keep up
loss of deeper corals

17. Opportunities for management interventions
Anthony & Maynard 2011

18. Reef status: Fiji value of monitoring – appears “stable” condition
tropical cyclones, bleaching, COTs
recovery after disturbance
localised pollution/overuse
34% of reefs classed at “low threat”
Morris & Mackay (2008) Status of coral reefs of the world 2008

19. What it means for coral reefs
already shown vulnerability
bleaching and diseases
physical destruction
weaker skeletons
lower salinity
connectivity between reefs
direct & indirect effects on other reef organisms

20. Coral reefs will not disappear entirely BUT MUCH SIMPLER ECOSYSTEMS
Summary key issues
rates of change
combined stressors
less time to recover between disturbances
can adaptation occur in decades rather than 1000’s years?
healthy reefs better able to cope
consequences for reef-dependent fisheries
Coral reefs will not disappear entirely BUT
likely to be
MUCH SIMPLER ECOSYSTEMS

21. Thank you