Of Carbon Dioxide or Calcium Carbonate

by Amy Larson

As I was sitting in one of my oceanography classes as a junior listening to Sally Jewell, my mind and heart on fire, trying to figure out how to bring more awareness to climate change and ocean acidification, an idea popped into my head. The passion I felt that day fueled me on my journey to illustrate, write, and publish a children’s book on ocean acidification, as well as spend over a year (and counting) researching coral nucleation rates, aragonite crystal morphology and how ocean acidifcation will change our world.

At first, I had no clue how I was supposed to convey such a nuanced and chemically complicated issue to children. My goal was to make ocean acidification, which seems to be left out of a majority of science communication to the general public in museums, articles, and aquariums- accessible to children and their parents. This initial moment of having no clue what or how I was going to do this was familiar; it was exactly how I felt when I frst started my research on corals and ocean acidification.

Concurrently to starting this new project, I began my own research on ocean acidifcation, growing little coral fragments on thin microscope cover slip slides in petri dishes. I had been working up to starting this project for the past year, volunteering in Dr. Alex Gagnon’s lab as the caretaker for the lab’s 400 gallon mesocosm. Corals do not like to stay glued onto smooth glass, but little did I know that would end up being the least of my worries. Turns out, corals also do not like being put into carefully engineered flow cells (I still don’t know why) that provide them with fresh seawater and constant temperatures. I spend hours trying to image the calcifying space of the growing edge of the coral fragments, and hope that during that 10 hour window I was taking pictures for, the coral would grow.

The event I was trying to capture is known as nucleation, which is integral to new coral growth. Nucleation is the formation of brand-new individual calcium carbonate crystals under the tissue that covers the skeleton of a coral. We can predict the rate of nucleation from math and chemistry (saturation state of calcium carbonate), but we do not know what the rate is inside corals or what impact it has on skeleton growth. Several thousands of photos and days of image processing later, I now had a few diferent rates captured from 10-hour time-lapse photography and was also able to measure skeleton extension growth rate and the density of the crystals. Much of this project was only possible because of current and previous research done by past undergraduate and graduate students. As one of my favorite African proverbs at my South African parents’ house states “if we stand tall, it is because we stand on the backs of those who came before us.” Thus, I try to improve on the past and present work of my colleagues.

Though I love my corals, I want to stress that true research is not for the faint of heart. I have spent far too many hours doubting myself as a scientist and wondering if I would ever be able to work hard enough to finish the project on time. Learning to manage my expectations (as a wise grad student put it) for myself, others, life being random, biology being even more random, and ideas becoming way more complicated than I thought has been a large struggle and something I still need to improve on. I have broken so many corals and microscope slides, and I’m going to break more. I still don’t take enough lab notes. The list goes on, but all of that seems to fade away when you watch brand new calcium carbonate crystals form in front of your eyes. I look at pictures of coral skeleton under polarized light for hours each day, and I am still foored by the beauty with each new photo or glance through the microscope eyepiece.

The same fascination of watching these microscopic crystals form helped drive my work in creating the book. My appreciation for my community grew as I told my friends of my book idea. One of them suggested making the CO2 molecule a character, and after that I was on a roll. I was hesitant to portray CO2 as an all-bad evil, because without it the world would be quite different and there probably would be no life. Once CO2 became the main character it was neither bad nor good but simply looking for a place where it belonged. It was not just a mysterious substance with a weird name; it now had a face, expressions, and a mission. Writing was the most difficult for me because it was hard to know what was too much or too simple, but after months of drawing, scanning, and putting pen to paper, I fnally had a draft. If I’m honest, it came together somewhat unexpectedly and only because of the tremendous help from my professors and their families to smooth out the bumps.

Fast forward more days and hours of coral data analysis and I had found a correlation between skeleton growth and density. This means that nucleation plays a vital role in skeletal growth opposed to just pre-existing crystals growing larger. Unfortunately, nucleation is susceptible to changes in seawater chemistry. Ocean acidification is result of increasing anthropogenic carbon dioxide that reduces carbonate ion in seawater, an essential component to nucleation and skeleton growth. Additional work is required to determine exactly how future ocean conditions will change nucleation rates, but now we know another piece to the puzzle, that is how corals biomineralize. By creating my children’s book, CO2 and the Ocean Blue, in parallel with my detailed coral skeletal growth research, I now have a better understanding of the bigger picture of chemistry and life in our oceans. As this published book may have a positive impact on the younger generation, I hope that my research on coral growth rates will also contribute to coral reef research, conservation, and restoration around the world.