Figure 15. Ocean acidification – as carbon concentra- tions increase in the atmosphere, so do concentrations in the oceans, with resultant acidifica- tion.
Aragonite saturation Aragonite saturation
Sources: Donner, S.D., et al., 2005; Orr, J.C., 2005. Map by Hugo Alhenius.
Sources: Donner, S.D., et al., 2005; Orr, J.C., 2005. Map by Hugo Alhenius. Source: Donner, S.D., et al., 2005; Orr, J.C., 2005.
Coral bleaching is a phenomenon caused primarily by above-average water temperatures and high radiation from the sun, that stress the micro-algae (“zooxanthellae”) living symbiotically in corals and giving them their spectacular colours. When these micro-algae become stressed, the coral expels them, so that the coral’s white calcareous skeleton is visible through the transparent tissue – hence the term ‘bleaching’. Bleached corals are very weak and prone to disease, algal overgrowth and mortality if the stress is high or continues over longer time periods. In 1998, a mass global bleaching event caused the mortality of an estimated 16% of the world’s coral reefs, and unfortunately because of rising sea temperatures mass bleaching events are predicted to increase in frequency and intensity. Loss of coral reefs also means loss of revenue and food for coastal communities who depend on them. LOSS OF CORAL REEFS AND ASSOCIATED MARINE BIODIVERSITY 7
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