Until recently, scientists were hoping that coral reefs could adjust to climate change by gradually acclimatising to warmer conditions. This hope was based on the idea that most of the corals that make up tropical reefs could increase the amount of heat they can withstand by changing the type of algae within their tissue.
This “shuffling” occurs when the coral rejects its normal algae and new algae take their place. The new type of algae can help the coral withstand water that is 1–2°C warmer than normal. Although shuffling gives us hope that reef corals may be able to cope with climate change, the short-lived nature of the shuffling, the effects of algal type on the coral and the pace of warming, taken together, suggest that this adjustment will not be without a cost.
Corals are tiny animals called polyps that resemble jellyfish but are smaller and in contrast grow upside-down within a limestone skeleton cup. They live in a partnership with tens of thousands of even smaller single-celled plants called zooxanthellae.
The polyp acts as the host for the tiny olive-green algae, which in turn make food for their host using sunlight and water through photosynthesis. The algae supply most of the energy required by the polyp to grow its skeleton, regenerate and produce eggs and sperm for reproduction. In turn, the waste products from the polyp are used by...
