Water And Oceanography

What is Coral Bleaching



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Climate change is creating an imbalance in the globe's reef ecosystems and causing harmful stress resulting in damaging Coral Bleaching. This discoloration of the coral occurs when the photosynthetic pigments decline and the coral becomes pale with their skeletons shows through their ailing translucent surfaces. The normally live coral algae, zooxanthellae, are what brings the healthy brownish colours but in stress when expelled causes the white skeleton like transparency and bleached look of the coral.

Coral bleaching has been observed in the last century with the last few decades bringing a world-wide occurrence with some species more susceptible than other. The high light levels bring increased ultra violet rays coupling with warmer temperatures and imbalance in salt levels all seem to be major contributors and have scientist attributing the current and on-going bleaching be primarily due to changing sea temperatures due to global warming.

This stress response on the part of the coral in both the increased and reduced water temperatures has altered the chemistry and acidification. Overfishing has upset the balance in the food chain in the reef to the point of serious decline in the plankton and algae causing a starvation to the corals. As coral survives in a symbiotic cycle with the algae sustaining the colony, this ability to feed itself is most paramount and the bleaching hinders the lifecycle and the quality of life of the coral.

Run off into the seas has brought about a shift in the sedimentation and salinity level change and has allowed disease to settle into the reef bringing infections and even deaths within the ecosystem. Warmer temperatures, due to global warming, also create a better host to bacteria, virus and pathogens resulting in greater risk to coral bleaching from diseases thriving in the ease to spread stronger in warmer waters.

The bleaching damages the coral skeleton affecting growth, altering the reproduction cycle and making the reefs more susceptible to bacteria and disease. Certain corals are less affected by the stresses causing coral bleaching and are able to recover and rebuild over time or when the stressing factors are diminished. The larger massive corals are more able to withstand increased temperature and light swings where as the branch-like more delicate and soft corals are more likely to perish in the stress of a bleaching incident.

Reef monitoring and continued study of the decline in coral health are paramount in the management and survival of the evolutionary ability of the ocean's coral reef to adapt to global changes. Tropical marine life and the delicate balance within the ocean's food chain depend upon the coral reefs survival.

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