75-15
Hot Sour Soup: How Rising Temperatures and Ocean Acidification Threaten Corals and Reefs
C. Mark Eakin
,
Coral Reef Watch, National Oceanic and Atmospheric Administration, Silver Spring, MD
Gang Liu
,
Coral Reef Watch, National Oceanic and Atmospheric Administration, Silver Spring, MD
Tyler R.L. Christensen
,
Coral Reef Watch, National Oceanic and Atmospheric Administration, Silver Spring, MD
Scott F. Heron
,
Coral Reef Watch, National Oceanic and Atmospheric Administration, Silver Spring, MD
William J. Skirving
,
Coral Reef Watch, National Oceanic and Atmospheric Administration, Silver Spring, MD
Jacqueline L. Rauenzahn
,
Coral Reef Watch, National Oceanic and Atmospheric Administration, Silver Spring, MD
Alan E. Strong
,
Coral Reef Watch, National Oceanic and Atmospheric Administration, Silver Spring, MD
As humans increase levels of carbon dioxide in the atmosphere, climate change and ocean acidification are modifying important physical and chemical parameters in the oceans with resulting impacts on coral reef ecosystems. On one hand, rising CO
2 is warming the world’s oceans and causing corals to bleach, or expel their symbiotic algae (zooxanthellae) with both alarming frequency and severity. Warmer oceans also have contributed to a rise in coral infectious diseases. Both bleaching and infectious disease can result in coral mortality and threaten one of the most diverse ecosystems on Earth and the important ecosystem services they provide. At the same time, rising CO
2 is reducing the pH of the oceans and reducing the availability of carbonate ions needed by corals and many other marine organisms to build structural components like skeletons and shells. It further reduces cementation, reducing the integrity of reef structures. Ocean acidification may even be increasing the susceptibility of corals to thermally induced bleaching.
Using a variety of observations and models, this talk will explore the consequences of these two stressors on corals and the importance of limiting absolute levels of atmospheric CO2—not just emissions. There is growing evidence that these stressors not only threaten reefs, but perhaps species loss as well. At least one coral species is likely to have gone extinct, others extirpated, and others at high risk due to climate change. This will only get worse as CO2 rises.
At somewhere between 450-500ppm coral reefs are probably going to be unable to grow quickly enough to exceed natural forces of erosion and dissolution, resulting in net reef loss. The safe upper limit for atmospheric CO2 is probably somewhere below 350ppm, a level we passed decades ago, and for temperature is a sustained global temperature increase of less than 1.5°C above pre-industrial levels. As humans continue to increase stress on coral reefs, local actions are even more important to sustain coral reefs until we can restore more favorable environmental conditions.
