I know quite a bit about the effects of global warming on land ecosystems, but I'm not too familiar with their effects on ecosystems below sea level. I know that global warming causes ocean temperatures to rise, making it hard for fish to breathe due to decreased oxygen in the water. I also know that melting ice and snow is causing rising water levels and the submersion of coastal land. But something I didn’t realize is that coral reefs are also greatly affected by global warming.

One significant way global warming affects corals is through coral bleaching. As I had mentioned in an earlier post, coral bleaching occurs when certain stressors cause coral to release zooxanthellae in its tissue. There are many different factors that can lead to coral bleaching, but the most prominent cause is rising ocean temperature. It is possible for corals to bleach when ocean temperatures drop to abnormally cold levels, but corals react more strongly to increases in temperature. Bleaching naturally occurs due to seasonal climate changes, but an overall increase in water temperature could be dangerous for corals. 

In addition to the problem of water temperature, rising water levels also make it difficult for zooxanthellae still within coral to perform photosynthesis. Light strength becomes weaker the deeper you go down in water, and so not enough light is able to reach zooxanthellae when water levels are too high. Corals normally grow upward so that they can receive the light they need, but they are in no way equipped to grow fast enough to accommodate themselves to the quickly rising water. This combined with the stress of warmer waters greatly increases the chance that coral bleaching will occur and also makes it harder for coral to recover from incidences of bleaching. And these factors, in turn, could kill off corals and endanger the marine populations that depend on them.

Bleached Coral

Personally, I think the sight of bleached coral looks beautiful. The contrast of the stark white coral skeletons against bright fish and water creates a neat, slightly eerie effect. But even though I do think it would be cool to see, I sincerely hope that I never encounter bleached coral. Bleached coral may look cool, but I'm sure that it can't compare to experiencing a colorful, vibrant coral reef and its interaction with the marine life it supports. Coral reefs are what allow so many wonderful and different species to exist, and it would be a great shame to have this diversity die with the coral.