Coral reefs scatter light like forests

珊瑚礁具有森林一样的反射光作用

By Devin PowellMar. 1, 2016 , 12:00 PM

珊瑚礁和森林的相似之处，可能比你预想的要多。当阳光照到一片树林，阳光在空间的分布并不均匀。得到阳光多的树叶内的组织，会向外散射阳光，与别的树叶分享阳光。海洋学家在2月下旬召开的AGU海洋年会上，介绍了珊瑚的这一功能。虽然浮潜时，你不一定注意到身体下面的珊瑚“森林”，因为它们不像陆地上的森林那么明显（地遮阴）。但是，这些研究人员认为，珊瑚的这一反射光功能对研究海底生物非常重要。

A coral reef has more in common with a forest than you mightthink. When sunlight strikes a group of trees, some parts tend to get more sunthan others. Leaf tissue somewhat compensates for this by scattering lightoutward, helping to illuminate other leaves. A similar thing happens withcoral, researchers reported at the American Geophysical Union’s OceanSciences meeting in New Orleans, Louisiana. When scientists shone a laser at acoral, the coral’s colorful tissue spread the light, generally redistributingit to other parts. Coral’s white calcium carbonate skeleton also gets in on theaction. But it tends to spread light less, helping instead to focus it onspecific areas that would otherwise be in the shade. Coral can also rearrangethemselves depending on the circumstances, expanding to increase the spread oflight or contracting to minimize it. Yet even with all of these tricks, lightcan only penetrate so far into coral tissue; it tends to drop off the deeperyou go, as in forests, making getting by more difficult for cells at the bottomof tissue. So just as different cells in a leaf contain different amounts ofchlorophyll, coral cells seem to house different amounts of the photosyntheticalgae that makes their food, Symbiodinium.Cells specialized for low light to still make decent amounts of food in dimconditions, as measurements of photosynthesis (pictured here http://www.sciencemag.org/news/2016/03/coral-reefs-scatter-light-forests), showed. Snorkelersvisiting coral may not notice the canopy below, a much smaller and subtleraffair than the lofty bowers of forests on land. But the researchers argue thatunderstanding it is crucial for understanding how life gets by on the seafloor.