A Method to Algae Madness… How to Measure Miniscule Growth

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Rhodoliths (photo by Paul Tompkins)
Jasmine Ruvalcaba

by Jasmine Ruvalcaba, Phycology Lab

edited by Brynn Hooton

We’ve all heard the giant kelp Macrocystis can grow up to one meter per day.  So, how do phycologists, people who study seaweeds, measure growth of different species of algae?  With most, you can use a ruler of some sort.  For instance, Dr. Graham, advisor of the phycology lab,  has a National Science Foundation grant going right now to look at effects of climate change on intertidal and subtidal species.  One factor he looks as is algal growth.  To do so,  we punch holes in the vegetative blade with a regular, run of the mill one-hole puncher near the base of the seaweed, and then each month go back to the same plants, and punch a new hole.   We  measure from the base of the blade to new the punch, from the new punch to the  old punch, and the old punch to the tip of the blade. Wow, sounds like a lot to do underwater, right?  Practice makes perfect.

This is a kelp called Laminaria sinclarii. The arrows show the different hole punches, which show how much the kelp has grown. This one has grown 11 millimeters. (photo by Jasmine Ruvalcaba)

That method is great for species that are fleshy and can grow centimeters per day, but how do you measure growth with calcified species, that grow very slowly?  That’s what Paul Tompkins and I, Jasmine Ruvalcaba, are doing as a part of our thesis research.  Paul studies rhodoliths, which are calcified red algae that form “beds” over soft sediments all over the world.  I am studying their relatives, the articulated species.  In a nut-shell, we soak our plants in stains anywhere from 5 minutes to days, depending on what type of stain we’re using, and let the stain mark the alga’s outer cell walls.  After the plant is stained, we then put it back in clean seawater and let it grow.  Any new parts of the plant that have grown after we took the plant out of the stain should be visible, and we know how long it’s taken to make this new growth.  So, here is what we see…..

This is Calliarthron sp., an articulated coralline species. This photo was taken under UV light, because the particular stain that was used on the algae lights up, or shows up under UV light. (photo by Jasmine Ruvalcaba)
This is a close-up of the articulated coralline branch tips. The arrows show where the stain stops. The white tips, that aren't stained, are growth of the coralline algae that occurred after we stained it. We measure from where the stain stops to the tip of the plant. This particular individual has grown 1.2 millimeters in 1 month. (photo by Jasmine Ruvalcaba)

Keep in touch to read about my future adventures with coralline algae!