Ocean Acidification, Small Island Developing States, and Pathways to Resiliency in the 21st Century
Robert Dunbar
Stanford University 18 June 13
[email protected]
1) The physics of CO2 uptake by the ocean is
straightforward. Impacts on marine life are
complex, yet much is now known.
2) The SIDS will be affected more and sooner by
Ocean Acidification (OA) impacts.
3) OA poses significant threats to calcifiers, particularly coral reef organisms and mollusks.
4) Resiliency to OA is enhanced by managing other
stressors (habitat degradation, pollution, over‐
fishing) and by implementing MPA’s.
The Problem of Ocean Acidification and the SIDS is of Global Importance
 Corals/Coral Reefs are found in >98% of SIDS nations.
 >1/4 of ALL marine species associate with coral reefs.
 Reefs important source of protein, net worth >100 $bill/yr
 One third of SIDS nations consist wholly or in part of islands at sea level built entirely by coral reef organisms.
 100’s of studies suggest decreased calcification rates by many organisms as OA increases.
 Most SIDS are in parts of the ocean experiencing the most rapid OA – and this will continue to be true.
Current Status of Coral Reefs of the World – Wilkinson 2008
(Does not include projected impacts of Climate Change and OA)
50%
THREATS:
‐Overfishing
‐Pollution
‐Nutrient enrichment
‐Sedimentation
‐Disease
40%
30%
20%
10%
0%
Reefs
Lost Reefs at Reefs
critical threate
ned stage
Reefs at low threat level
Coral reef animals and plants make hard parts out of
different carbonate minerals (Aragonite, Calcite, Mg‐Calcite)
These minerals are harder to produce as OA increases.
They can also dissolve and they dissolve at different rates.
Feely et al., 2009, 2012
= SIDS
Feely et al., 2009, 2012
Ocean Acidification reduces Aragonite Saturation in the ocean causing
corals to calcify and grow
more slowly
11 different coral species
17 studies
Andersson et al., 2012, modified from Langdon Aragonite Saturation
New results from Ricke et al., 2013, using CMIP5 projections
Expected Aragonite Saturation where Reefs Grow
Pre‐industrial (1880): >99.9% of reefs are in areas where open ocean is more than 3.5 time supersaturated (good!)
By 2100, all reefs in waters with <3 times saturation (mostly bad)
Coral Calcification and Aragonite Saturation State
11 different coral species
17 studies
1950’s
2100
Andersson et al., 2012, modified from Langdon • Reduced growth rates by corals are not the only problem…….
• Some plants that make the “glue” that holds reef together are also at risk.
• Lower growth rates will be compounded by increased erosion (from storms and bioerosion
by animals) and dissolution of sediments
Different types of Coral respond differently to OA
C. Caespitosa
B. Europaea
Rodolfo‐Metalpa, Nat. Clim. Change (2011)
Diversity declines in a lower intertidal community after 2 month exposure to reduced pH
Hale et al., Oikos (2011)
Mortality (%) on Oyster (Crassostrea gigas) larvae
Barros et al., JEMBE (2013)
Consensus Statement On Climate Change And Coral Reefs
Drafted in 2012 by a working group – now signed by over 3250 coral reef scientists – 5 pages with summary.
“The International Coral Reef Science Community calls on all governments to ensure the future of coral reefs, through global action on reducing the emissions of carbon dioxide and other greenhouse gases, and via improved local protection of reefs.”
“Most reefs will experience higher acidification, impairing calcification of corals and reef growth.”
“Coral reef death also occurs because of a set of local problems including excess sedimentation, pollution, habitat destruction, and overfishing.”
From 2012 Consensus Statement
Pathways to Resiliency for the 21st Century
• Identify reefs at greatest risk – different reefs will experience OA in different ways and at different times
• Eliminate local stressors with strong community involvement
• Strategic implementation of MPA’s
• Reefs modify waters coming in from open ocean and land. Some reef organisms raise pH and help counteract the effects of OA on the local reef. This leads to as yet unexplored management options.
It’s not all about the open ocean trends. Coral reefs modify their own chemistry. If carefully managed and protected, some coral reefs may prove to be their own saviors.
7 days of pH on Ofu Reef, American Samoa
Dunbar et al., 2013
• Corals may be able to increase their upper tolerance limits over time by adapting to changing temperature or acidity.
• For this to be a long‐‐term solution to global stressors, the adaptation rate must be higher than the rate of change in the environment. • There is currently little knowledge about the capacity of corals to acclimate or adapt to ocean acidity.
‐from 2012 Consensus Statement Pathways to Resiliency
1) Different solutions for different SIDS
2) Manage local stressors
3) Understand and share information about OA impacts and how reefs modify their chemistry
Thanks!