Bleaching

Coral Bleaching

• What is bleaching?
  • Simply, it is the release of coral symbiotic zooxanthellaethe. A more in depth definition is the loss of all or some symbiotic algae and photosynthetic pigments by the coral animal resulting in their white calcium carbonate skeleton becoming visible through the now translucent tissue layer making them appear white or 'bleached'.
  • Corals and symbiotic relationship
    • What are zooxanthellae? - Dinoflagellates that live in coral tissues
    • What they do/importance? – photosynthesis, CO2 removal
  • Expulsion of zooxanthellae – give corals color, they now appear white
• Causes
  • SST
    • Stress on corals
    • Affects on symbiotic relationship
    • Past, present, and future predictions/ frequency of bleaching events
  • Acidification
    • What is acidification? – CO2 dissolves in ocean and increases acidity which dissolves CaCO3
    • Impact of acidification on bleaching – increases bleaching events
    • Synergy with SST – higher SST amplifies acidification effects and bleaching
  • Stress
    • Types
      • Elevated temperature
      • High solar irradiance
      • Disease
      • Hostile/changing environment
    • Disruption of symbiotic relationship
      • Why expel zooxanthellae?
• Effects
  • Disease – frequency increases
  • Ecosystem/reef effects
    • Corals – productivity, recruitment, survivability/adaptation
    • Fish/Other organisms – habitat, recruitment, abundance
• Special Case Study
  • US Virgin Islands following bleaching in 2005
  • Sunscreen and reefs
• What we are currently doing to sustain coral ecosystems
  • USGS “Science Based Strategies” example

Sources:

Hoegh-Guldberg, Ove (1999) . Climate change, coral bleaching and the future of the world's coral reefs. Marine and Freshwater Research 50 , 839–866.

H. van Oppen, M. J., & Lough, J. M. (2009). Coral bleaching: Patterns, processes, causes and consequences. (Vol. 205). Springer Berlin Heidelberg. Retrieved from http://link.springer.com/book/10.1007/978-3-540-69775-6/page/1

USGS. (2008, June). Coral diseases following massive bleaching in 2005 cause 60 percent decline in coral cover and mortality of the threatened species, acropora palmata, on reefs in the u.s. virgin islands. Retrieved from http://pubs.usgs.gov/fs/2008/3058/pdf/fs2008-3058.pdf

USGS. (2008, September). Science-based strategies for sustaining coral ecosystems. Retrieved from http://pubs.usgs.gov/fs/2009/3089/pdf/brewercoralfs3.pdf

T. Tyrrell (2007). Calcium Carbonate Cycling in Future Oceans and its Influence on Future Climates.

K. R. N. Anthony, et al. (2008). Ocean acidification causes bleaching loss in coral reef builders. PNAS vol. 105 no. 45

O. Hoegh-Guldberg, et al. (2007). Coral Reefs Under Rapid Climate Change and Ocean Acidification. Science 318, 1737