Partially bleached coral in Kaneohe, Hawaii. (Credit: Dan Dennison / Hawaii Department of Land and Natural Resources)
Although coral bleaching has occurred around the globe, Hawaiian coral has been largely spared until recently. This year, however, unusually warm temperatures combined with a mass bleaching the previous year means Hawaiian coral will likely suffer severe bleaching for a second year in a row, according to Phys.org.
Even though bleaching does not mean coral is dead, it does mean that algae expelled by the coral due to stress from high temperatures causes the coral to be weakened. Coral rely on algae for food and for healthy functioning. When stress causes algae to be expelled, not only is the vibrant color of the coral lost but its essential functioning is crippled, leading to a potential takeover by more aggressive algae species and possibly coral death.
About 30 to 40 percent of reefs all over the world have already died after being weakened by bleaching events. Although warmer temperatures due to global warming have caused coral stress and coral death over the years, human activities such as releases of chemical contaminants into the ocean and walking or anchoring on coral have also played a role in coral reef stress.
Top image: Partially bleached coral in Kaneohe, Hawaii. (Credit: Dan Dennison / Hawaii Department of Land and Natural Resources)