Thursday, July 26, 2012

Coral and climate

It's easy to forget that coral is not a plant, but an animal. So stories like this are an eye-opener. Consider a quote from yesterday's New York Times: "As Dr. Hagedorn and her assistant watched, one coral tightened its mouth and seemed to exhale, propelling a cloud of sperm into its bath with surprising vigor. The water bubbled like hot oatmeal." The voyeurism of Smithsonian scientist Dr. Mary Hagedorn is for a good cause: to restore and rebuild the world's coral reefs (2nd and 3rd images, reefs in Florida), which may be devastated by 2050 due to several causes:

  • Global climate change (graphic here) is warming the oceans and making corals vulnerable to disease and bleaching, a condition in which the stressed organisms expel the algae critical to their food supply. 
  • Carbon dioxide levels are rising and acidifying the oceans, weakening coral skeletons and inhibiting their growth.
  • Budgetary constraints limit efforts to study the reefs (1st image, the underwater Aquarius Reef Base in the Florida Keys National Marine Sanctuary), establish protected refuges for existing coral, raise it in captivity, and reintroduce it into its natural habitat.
  • Overfishing damages reefs directly, but also causes a shift in the reef ecosystem.
  • Pollution also alters the ecosystem, for instance introducing runoff that causes massive algae growth that blocks sunlight and depletes oxygen.
  • Coastal development

These and other problems have killed half the coral in parts of the Pacific and 80% of that in the Caribbean. With loss of coral comes loss of other marine species, 1/4 of which are dependent on the reefs. 

Hagedon has gathered samples from corals in Hawaii, the Caribbean, and Australia to establish the 1st coral sperm bank. She estimates that she has frozen 1 trillion coral sperm (enough to fertilize as many as 1 billion eggs) and 3 billion frozen embryonic cells. Although corals can reproduce asexually, only sexual reproduction maintains the genetic diversity that protects its capacity to survive and adapt to change. Protecting the reefs buys time, but Nancy Knowlton, a coral-reef biologist at the Smithsonian, warns, “But if we continue on this greenhouse-gas emissions trajectory, the only place we’re going to be able to find many corals will be in Mary’s freezers."
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