Gorgeous Geniculated Coralline Algae

I’ve been busy lately! My final year of my undergraduate degree wrapped up this spring, which has opened up time for a lot of awesome projects. I’m helping my local community college by scanning in the best examples of their algae collection with my mother’s awesome scanner! (Plus, I’ve been updating the labels so they’re more up-to-date!)

I just got to the coralline algae section of the collection and it is so cool to see these specimens in such detail.

Edit: The image is so good that WordPress can’t handle it! See the zoomed-in image below!

I actually need to create a new label for this one at some point. The name listed on the label for this species is Corallina gracilis f. densa, but this name is now a synonym of Corallina vancouveriensis. The need for a label update is not all that surprising since this specimen was collected in 1967 and scientific algae names change often!

The WordPress picture size limit doesn’t quite allow you to see how amazing these scans are, so here’s a close-up:

Awesome scanning power!

As you can see, coralline algae doesn’t have the typical slimy, floppy look that most algae forms have. That’s because coralline algae are calcifying algae! Just like reef-building corals, coralline algae use calcium carbonate to beef up their tissue and create a sort of “skeleton,” hence the name “coralline,” meaning “coral-like.”

This particular coralline algae species is geniculate–hence the title of this blog post! Geniculate corallines refer to coralline algae that has “joints,” which enable them to have some mobility, unlike coral skeletons. This term comes from the word root for knee!

Here’s a close-up under a microscope:

Those pink parts are called intergenicula, as they’re between the genicula. The intergenicula are the parts with calcium carbonate deposits. You can actually see a geniculum quite well in this picture–it’s the yellow stringy stuff between the first and second intergenicula from the left. There’s none of that tough calcium carbonate present in the genicula so they can bend!

This specimen is a different species, although I’m not sure which. This one has been bleached a little–a lot of the pink color has left. Like coral, coralline algae usually looks white when it’s been dead for a while. Bright pink samples were most likely collected from live organisms.

Here’s a stained slide of some genicula and intergenicula:

The blue parts are intergenicula and the pink parts are genicula!

That same stringy genicula texture persists here!

These genicula are very important for the coralline algae, since it enables them to grow tall without being inflexible and brittle. One problem with coral is that it is rather susceptible to waves and storms–the wave energy can smash the immovable coral. Geniculate coralline algae has the ability to move with the waves, reducing its susceptibility to wave energy.

One thing’s for sure: coralline algae is more than a pretty pink color!