By Abby Lunstrum
Hello again everyone! It’s nice to be back on the blog! I’m Abby – a PhD student in USC’s Department of Earth Sciences, and the 2019 Bertics Fellow – and this will be my second summer on Catalina. I’ve been studying how ocean acidification affects California beaches…and by extension, other beaches around the world. A lot of research has been done on the effects of ocean acidification on marine biology, but we still have a lot to learn about its fundamental effects on marine geology and geochemistry.
The global ocean, including the California Coast is getting more acidic as a “byproduct” of climate change. By 2050, the acidity of California seawater is expected to increase by 30% compared to 2005. Or compared to pre-industrial conditions, seawater will be 60% more acidic than it used to be. That may not sound like a lot…but imagine accidentally adding 60% more vinegar to a recipe, or your food being 60% saltier. You’d definitely notice, it wouldn’t be pleasant, and over time, you might see health effects. Another analogy for the seriousness of ocean acidification is soda water or cola: we know that too much soda can lead to tooth decay, but it’s not sugar that’s causing the damage…it’s ultimately the acidity of the drinks that causes decay!
Lots of things dissolve in acid, including teeth, and the focus of my research: rocks. At some point, if the ocean gets acidic enough, sandy beaches—specifically certain types of rocks in beach sands called carbonates—will start dissolving too. A big part of my research is trying to figure out when that will happen, and what the effect on water chemistry will be.
My main strategy for this research is exposing beach sands to current and “future” (i.e., acidic) seawater conditions. Last summer, I spent most of my time doing these kinds of experiments in the lab. This summer, I’ll be taking that work outside to see if my lab results match more realistic conditions. The main way I do this is by placing “benthic chambers” on sand, underwater (see the chamber in the photo below). These chambers use a spinning device to pump water through sand, just like it would do naturally from waves and current pressure. I’ve done a few of these experiments already, and the results match last year’s lab results pretty well!
With any research, it’s important to check, double-check, and triple-check your results, and, if possible, confirm those results using multiple methods. So I’ll be doing more chamber experiments over the rest of the summer, and will be using yet another method to measure carbonate dissolution by looking at the water chemistry in the sand itself (i.e., porewater).
The data I’ve collected so far clearly show that beach carbonate sands already dissolve a little from natural conditions, and they will dissolve much more in the near future as the ocean acidifies. Within a few decades, the impact of all this dissolution on water chemistry will be more noticeable. In California, our beaches only contain a small fraction of carbonate, so the visual impact on beaches wont be obvious. (In other words, your favorite beach isn’t going to melt away.) But the effect on seawater chemistry will be significant, so we need to consider sands when we calculate how bad ocean acidification will get. This information can also be used in climate change models to better understand how the ocean’s role in soaking up carbon dioxide is changing. In essence, my research is showing that carbonate sand dissolution—caused by ocean acidification—is an important part of the global carbon cycle, and we have to understand it to understand how exactly climate change is messing with the planet.
Before signing off, I want to send a big thank you to everyone who has supported my work. I’m funded by the Victoria J. Bertics Fellowship, which supports PhD research on sediments, and carries on Dr. Bertics’ enthusiasm for benthic ecology and chemistry. I also thank the incredible Wrigley staff for their infinite patience and dedication! And thank you for reading!