Corals’ environmental premonition

By David A Gabel, ENN
28 November 2011 As Earth’s climate has warmed, one group of species that has not fared well has been corals, the sedentary marine species which lives symbiotically with algae. Warmer waters cause the algae to become heat-stressed, causing them to die or be expelled by the coral. This causes coral bleaching, a fatal phenomenon that has occurred worldwide with increasing frequency. A team of researchers from the ARC Centre of Excellence for Coral Reef Studies and James Cook University have now revealed the complex molecular signals that lead to the coral’s self-inflicted death. The team conducted experiments with Acropora corals from the reef at Heron Island which is along Australia’s Great Barrier Reef. They found that the cascade of molecular signals commences when ocean temperatures reach a level which is 3 degrees lower than those associated with coral bleaching. Therefore, the cascade of events leading to bleaching come before the actual bleaching occurs. The corals have a premonition of warmer waters in their future. The cascade of events eventually leads to apoptosis, or programmed cell-death. This process is common with living organisms which will deliberately destroy weak or infected body cells, effectively amputating the cell which has become a liability to the body. “Our results suggest that the control of apoptosis is highly complex in the coral-algae symbiosis and that apoptotic cell death cascades potentially play key roles in tipping the cellular life or death balance during environmental stress prior to the onset of coral bleaching,” explains lead author Dr Tracy Ainsworth. “It is also clear that this chain reaction responds significantly to subtle, daily changes in the environment and to sea temperatures which were generally thought till now to have little impact on the function of coral and its symbiotic algae.” […]

Corals’ Environmental Premonition