Neon Corals Use Colorful Bleaching to Protect Algae From UV Radiation

Coral reefs around the world are in decline due to warming ocean temperatures and reduced nutrition levels, but while coral bleaching usually causes them to turn ghostly white, some species are now engaging in what scientists refer to as “colorful bleaching” by showing vivid hues such as pink, purple and orange – using this bright display as an effective defense mechanism against harmful UV radiation while simultaneously drawing in beneficial algae back into their reef system.

These fluorescent corals are actually created naturally during a heat wave. Healthy corals contain symbiotic algae in their cells to absorb energy from sunlight and provide shelter and nutrition, but when stressed they release these symbiotic algae into their environment and leave its cells. As a result, its limestone skeleton and exposed flesh bleach away and it leaves only its limestone skeleton behind as its skin begins to break down further exposing flesh below. In order to try and lure back in their ecosystem through vivid neon hues. Research published Thursday in Current Biology suggests these vivid neon hues may help draw back its symbiotic algae back in in an attempt at survival.

Researchers from the University of Southampton in UK observed corals in their aquarium facility turning neon after exposure to mild heat stress. They noticed this was more likely on corals with greater pigmentation levels; their colors usually emerged two or three weeks following bleaching events.

Researchers conducted a survey of corals that had experienced bleaching events between 2010 and 2019 and found that neon hues correlated with mild bleaching episodes, caused either by an extended spell of warmer waters or by sudden temperature spikes. Corals experiencing heat stress episodes that turned neon were significantly more likely to lose their symbiotic algae than those not experiencing such heat stress episodes.

Coral reefs produce their neon colors due to the presence of a specific protein that emits light at certain wavelengths, similar to how jellyfish and some fish produce luminescence to attract prey or warn off predators. According to researchers, these proteins appear to be activated through similar processes in corals as they work to shield algae from UV radiation exposure.

Neon corals add an eye-catching splash of color to any aquarium, making an easy addition for beginners or hobbyists who seek new challenges in husbandry and the hobby. Acropora corals require stable lighting conditions, water flow rates and quality water chemistry in order to thrive, making them an excellent way to increase husbandry skills or start something new in this hobby.

As corals can take several days to become used to their new environment, feedings should initially occur only three times weekly for at least the first month and gradually increased after getting used to each feeding regimen. This allows the coral to expel waste when digesting has finished and avoids food rotting from overfeeding too frequently.

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