Tag Archives: el nino

2: The effects El Nino has on coral bleaching

Coral reefs are dying. In the last four decades the amount of bleaching rose from 8% in the 1980s to 31% in 2016.

El Nino

Since 1980, 58% of bleaching were recorded during strong periods of El Nino.  It was noted that in February of 2019, El Nino is officially back. El Nino is a natural phenomenon that typically peaks between October and March and happens every two to seven years. They have the ability to cause rising sea surface temperatures in the Pacific Ocean. As the climate warms (from El Nino), so does the risk of coral bleaching. There’s evidence that proves El Ninos are becoming more frequent and more intense. This is already the sixth El Nino we’ve had in the 21st century.


Even though coral reefs only cover 0.1% of the ocean floor, they support roughly 25% of the biodiversity of fish. However, coral reefs are very vulnerable to climate change. High sea temperatures is the biggest cause so far. Bleaching happens when stressed corals remove the tiny living algae in their tissues called zooxanthellae which leaves behind a white skeleton. That algae is important though—it’s how corals eat and without it they starve. It is possible for corals to recover from bleaching, but persistent bleaching can ultimately kill the entire reef.

Bleaching events have become such a modern phenomenon that it’s being reported that such events are happening every six or so years, which if you’re wondering, is not enough time for corals to recover.

The most recent bleaching event was from 2015 to 2016 and was the worst on record affecting 75% of the reefs that were examined during a study. Research suggests that Australia and the Middle East have seen the biggest increase in coral bleaching, but the reason for this still isn’t clear.



Even trying to limit temperatures to stay below 1.5C would be essential to give coral reefs a fighting chance. On the contrary, an increase of 2C would be disastrous for the world’s coral. The biggest consequence of El Nino is the effect it has on global temperatures. Most notably carbon dioxide which accelerates global warming.

Final Thoughts

If events like El Nino existed less and the effects weren’t so disastrous, coral reefs would have no issue thriving. Rising sea temperatures and the increase in carbon dioxide is killing coral reefs. These events happen so often they can’t regenerate in time.