Exoskeleton Absorbs UV Light

a coral reef is seen just below water surface near a coast with lush green trees

Biological Strategy

Corals

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Protect From Light

Access to sunlight is crucial to living systems because it’s the primary energy source for life. However, too much sunlight in the form of ultraviolet radiation (UV) can cause damage to living tissues. Therefore, living systems have strategies to filter out some or all UV radiation. For example, some plants that live in areas exposed to long periods of direct sunlight have reflective surfaces (such as white hairs or powder) that reflect UV light.

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Coral and sea anemones

Class Anthozoa (“flower animals”): Corals and sea anemones

Most cnidarians are included in this class, which contains 6,000 species and 70% of all known cnidarians. These animals are exclusively found in marine environments. They have no jellyfish-like medusa stage, and so move very little or not at all throughout most of their life. They are carnivores and channel food down a groove lined with cilia, or hair-like appendages, to their mouths. Many also have a symbiotic relationship with photosynthetic algae, which are responsible for the vibrant colors associated with coral colonies.

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The calcium carbonate exoskeletons of corals may help protect their photosynthetic symbionts by absorbing UV rays.

“Many coral reef organisms are photosynthetic or have evolved in tight with photosynthetic symbionts. As such, the tissues of reef organisms are often exposed to intense solar radiation in clear tropical waters and have adapted to trap and harness photosynthetically active radiation (PAR). High levels of ultraviolet radiation (UVR) associated with sunlight, however, represent a potential problem in terms of tissue damage…by measuring UVR and PAR reflectance from intact and ground bare coral skeletons we show that the property of calcium carbonate skeletons to absorb downwelling UVR to a significant extent, while reflecting PAR back to the overlying tissue, has biological advantages… our study presents a novel defensive role for coral skeletons and reveals that the strong UVR absorbance by the skeleton can contribute to the ability of corals, and potentially other calcifiers, to thrive under UVR levels that are detrimental to most marine life.” (Reef et al. 2009:e7995)

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2776492/
http://news.sciencemag.org/sciencenow/2009/11/30-01.html?rss=1

Last Updated June 6, 2018

References

Journal article

Coral Skeletons Defend against Ultraviolet Radiation

PLoS ONE | 24/11/2009 | Ruth Reef, Paulina Kaniewska, Ove Hoegh-Guldberg |

Craig Robert White

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