We’re into red leaves.  Why?  Because often the red substances are anthocyanins.  These colorful compounds can shield plants from the harmful effects of too much light, especially dangerous UV light, and heat.  In Australia researchers have observed reddened seagrass leaves for quite a while (think ozone hole – lots of UV light).  Now researchers are finding that it is a common response in these plants, and that it protects them.  Similar respones have been observed on land, where immature leaves are often redish.  Could this answer the oft-asked question: Why are young leaves red? 

The nice thing about proposal writing is that we’re forced to re-read the literature and uncover gems like the recent papers by Alyssa Novak and Fred Short.  Here’s one: 

Leaf reddening in the seagrass Thalassia testudinum in relation to anthocyanins, seagrass physiology and morphology, and plant protection Author(s): Novak, Alyssa B.; Short, Frederick T.  Source: MARINE BIOLOGY  Volume: 158   Issue: 6  Pages: 1403-1416   

And what happens when seagrass leaves turn red?  It is possible that they will be less palatable and nutritious to grazers (sorry waterfowl, manatee, and turtles) and more resistant to decay.  But that depends on which phenolic subtances might be accumulating with the anthocyanins and a host of other factors.  Our recent study of ocean acidification showed that high CO2 levels caused a decrease in many phenolic substances.  But we didn’t measure anthocyanins.  It will be interesting to dive back into the freezer an analyze those tissues!