Marine algae, like plants can use the energy in sunlight to take carbon from the surrounding environment and transform it into sugar used for growth and reproduction. In the case of land plants, the source of carbon is the carbon dioxide in the atmosphere. For aquatic photosynthetic organisms, like marine algae, the carbon they use is in the form of the bicarbonate ion floating in the sea water around them. Don’t worry, this blog isn’t about chemistry, and I won’t mention any other chemical names from here on out.
The most incredible thing about the process of photosynthesis is that it allows plants and algae to use sunlight in a way that no animals can. From an ecological stand point, this makes plants and algae extremely important players in ecosystems. While I’m a full-on nerd when it comes to photosynthesis and ecosystems, even I must pause occasionally to smell the roses, or the algae in this case, although no smelling was involved.
Today’s photo illustrates another way in which marine algae can interact with sunlight that is completely unrelated to photosynthesis. What is shown here is a purely physical phenomenon, that may or may not serve any useful purpose for the algae. The species in question is most likely Fauchea laciniata (sorry, there is no common name), and this photo was taken on the south side of Santa Cruz Island at a location called Willow’s West Wall. The soft blue light is produced by the reflection and refraction of sunlight, known as iridescence. The cells within the multi-layered surface of this species reflect and refract the sunlight that strikes them, creating a variety of colors.
Look closely at the portions of the algae that are shaded by parts above, and you won’t see any blue light. This is because the shadow cast by the overlying parts prevent sunlight from striking those parts, so no light is available to reflected or refracted. Thus, you see the actual color of this algae, without the iridescent enhancement.
Iridescence is not to be confused with bioluminescence. Iridescence is produced by the reflection and refraction of an external light source, while bioluminescence is the production of light from within the organism by a chemical reaction. Two completely different processes.
Today’s photo was taken with a Canon EF100 mm f/2.8 Macro USM lens on a Canon EOS 5D Mk III in an Ikelite housing. Lighting was provided by an Ikelite DS161 strobe set on eTTL exposure. The exposure was set to 1/180 sec at f/11 and ISO 400.