Corals are marine invertebrates that build hard skeletons out of calcium carbonate. They are important reef-building organisms, and they provide food and shelter for a variety of other marine life. However, corals are threatened by climate change, which is causing the ocean to become warmer and more acidic. These changes are stressing corals and making them more susceptible to disease.

One way that corals can cope with stress is by forming symbiotic relationships with algae. These algae live in the coral's tissues and provide them with food through photosynthesis. In return, the coral provides the algae with a protected environment and access to nutrients.

The type of algae that a coral forms a symbiotic relationship with can affect its ability to survive stress. Some types of algae are more tolerant of heat and acidity than others. This means that corals that are associated with these types of algae are more likely to survive in changing environmental conditions.

Scientists are studying the role that algae symbionts play in coral survival. They are hoping to learn more about how these relationships can help corals cope with climate change. This information could be used to develop new strategies to protect corals and preserve coral reefs.

Here are some specific examples of how algae hookups can help corals survive:

* Increased heat tolerance: Some types of algae produce compounds that can help corals tolerate higher temperatures. For example, the symbiotic alga Symbiodinium kawagutii produces a compound called mycosporine-like amino acids (MAAs). MAAs absorb ultraviolet (UV) radiation, which can damage coral DNA and proteins. By absorbing UV radiation, MAAs help to protect corals from the harmful effects of heat stress.

* Increased acidity tolerance: Some types of algae can help corals to cope with ocean acidification. For example, the symbiotic alga Symbiodinium microadriaticum produces a compound called carbonic anhydrase. Carbonic anhydrase helps to convert carbon dioxide (CO2) into bicarbonate (HCO3-), which is less acidic than CO2. By converting CO2 into HCO3-, carbonic anhydrase helps to reduce the acidity of the coral's environment.

* Improved immune function: Some types of algae can help corals to improve their immune function. For example, the symbiotic alga Symbiodinium trenchii produces a compound called mannan. Mannan is a type of sugar that can activate the coral's immune system. By activating the immune system, mannan helps to protect corals from disease.

These are just a few examples of how algae hookups can help corals survive. Scientists are continuing to study these relationships, and they are hopeful that this information can be used to develop new strategies to protect corals and preserve coral reefs.