Category Archives: Wrigley Institute

The Role an Invasive Alga Can Have Among Our Reefs

By Kathryn Scafidi

Hello everyone! My name is Kathryn Scafidi, I’m a second-year graduate student in Dr. Mark Steele’s Fish Ecology Lab at California State University, Northridge.  Summer 2019 is my second field season and last before I finish up my master’s.  I am studying the effects an invasive alga (Sargassum horneri) has on the trophic dynamics of rocky reefs at Catalina Island.


Last year, I observed the foraging habits of rock wrasse, garibaldi, and sheephead, to first confirm if the fish were finding food among the invasive alga compared to the native algae. I had also conducted benthic surveys of my sites where I record the substrate type and the algal species present, so I have an understanding of what is available to the fishes in the areas I observed them. I just completed these benthic surveys for 2019.

Kathryn Scafidi Fellow 2019_maurice

Credit: Maurice Roper

Last year I also collected individuals of S. horneri and three of the most common and abundant native algae to compare the invertebrate epifauna found among them. I am still currently working through those samples, counting and identifying the organisms. I am also extracting chemicals that the algae use as a defense mechanism to understand if S. horneri has higher concentrations than the native algae, thus potentially contributing to the invasive success of this alga.

Kathryn Scafidi Fellow 2019

Additionally, I collected rock wrasse my sites to assess their growth and reproductive output. To do so, I collected them using a specialized pole spear, called a microspear. I then processed them in lab, extracting their otoliths (which can be read like the rings of a tree to age) and their gonads, which I can use to count hydrated eggs just before they spawned. I will be collecting more rock wrasse this summer which is my next step for 2019.

Kathryn Scafidi Fellow 2019 2_Maurice

Credit: Maurice Roper

All of my research was not possible without the Wrigley Fellowship last year, and again this year. I love coming out to Catalina to do my work.  The diving is among the best I have done so far and there’s never a dull moment under water. This research station is a great place to meet and be around like-minded individuals that are working hard at the research they are doing, which is very motivating! I am looking forward to a summer of hard work, old and new faces alike, and the outreach opportunities that Wrigley has.  As a marine biologist, it is always exciting to hear just how knowledgeable visitors are of the surrounding waters, but also their openness to hearing about the research being done and ways we can all be more ocean friendly. I hope my research can provide everyone with a better understanding of the interconnectivity of our coastal reefs and how invasive species affect them as these occur more frequently with climate change and globalization.

Ocean Acidification at the Beach

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!