From: Allison Winter, ENN
Published May 9, 2013 12:58 PM

Light-Scattering Properties are Risk Factor for Coral Reef Survival

Coral reefs have been gaining a lot of attention by conservation groups as environmental and human stresses are causing irreparable damage to these reefs. Stresses such as warming oceans and climate change are going to serve as future obstacles for these coral populations. However, the study of dying corals is complex, and researchers have found that some corals die while others do not, even when exposed to the same environmental conditions.

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In order to figure out this conundrum, a research team from Northwestern University and The Field Museum of Natural History found that corals themselves play a role in their susceptibility to deadly coral bleaching due to the light-scattering properties of their skeletons. 

Using optical technology, researchers discovered that reef-building corals scatter light in different ways to the symbiotic algae that feed the corals. Corals that are less efficient at light scattering retain algae better under stressful conditions and are more likely to survive. Corals whose skeletons scatter light most efficiently have an advantage under normal conditions, but they suffer the most damage when stressed.

The findings could help predict the response of coral reefs to the stress of increasing seawater temperatures and acidity, helping conservation scientists preserve coral reef health and high biodiversity.

"We have solved a little piece of the puzzle of why coral reefs are bleaching and dying," said Luisa A. Marcelino, a molecular biologist and research assistant professor at Northwestern University, who led the study. "Our research is the first to show light-scattering properties of the corals are a risk factor."

"Coral reefs are like the rain forests of the oceans - the consequences will be catastrophic if coral reefs are lost in great numbers," said Vadim Backman, a physicist and professor of biomedical engineering at the University, who invented the optical technique used by the team. "Corals are also optical machines. By identifying how much light the skeletons of individual coral species reflect, we have learned which species are more resilient under stress."

Algae provide nutrients to the corals and receive shelter and light for photosynthesis in return. When stressed, the corals can lose their algae. The corals often die of starvation shortly afterward, exposing their white skeletons.

Read more of the press release at Northwestern University.

The paper "Modulation of Light-Enhancement to Symbiotic Algae by Light-Scattering in Corals and Evolutionary Trends in Bleaching"can be found at PLOS ONE.

Coral image via Shutterstock.

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