Coral Bleaching

Coral reefs are the most diverse ecosystems in the oceans, housing approximately one out of every four marine species. They are primarily built by hard coral colonies that are composed of thousand polyps that contain millions of microscopic algae. These algae, known as Zoozanthellae, live in symbiosis with the corals. They gain nutrients and protection, and in turn provide energy to the coral so that it can build and skeleton. However of temperatures rise and corals become stressed, the Zoozanthellae are expelled and the corals become weak. Since Zoozanthanllae provide colorful pigments, when they are expelled the white skeleton becomes visible. This is called coral bleaching. Bleached corals are not dead yet, but they are extremely weak and prone to mortality.

Large microalgae can proliferate and grow over corals and killing them. When this happens, the reef can shift into a different form, dominate by algae. It becomes less useful to humans, with lower fish yields, less protection from storms, and lower revenue from tourism.

Global bleaching is often linked to major events, such as El nino. In 1998, a particuly intense caused a mortality of an estimated 16 % of the worlds tropical corals in a matter of months. Worringly, the frequency and the intensity of bleaching events are also increasing due to changes in the climates and subsequent rises in sea temperatures.

Climate change and coral bleaching are considered the most serious threat to coral reefs today, and some scientists even predict that they may go functionally extinct this century. However is possible for coral reefs to resist bleaching, that is resistance, or to recover relatively quickly after bleaching, that is resilliance.

Now many different ecological environmental factors affects the resistance of resilliance of corals and reefs to climate change. So its very important for managers to understand what these factors are so that they can protect their reefs more effectively. Things such as reducing pollution or reducing over fishing can very much help reefs to recover and resist climate change impacts. So the future reefs is very much in our hands.