Swimming in Low-pH Seas
Does ocean acidification affect squid movement?
Doriane Weiler grew up on the coast of California and remembers spending so much time at the beach as a child that she often had to be pulled out of the water before the tide swept her away. Now starting her senior year at University of California, Berkeley, Weiler entered college on a pre-med track, but she soon found that her hobbies could become a career in marine science. As a Summer Student Fellow at Woods Hole Oceanographic Institution (WHOI) this year, Weiler was thrilled to land a position with biologist Aran Mooney and graduate student Casey Zakroff studying the effects of ocean acidification on the swimming behavior of juvenile squid.
Even before coming to WHOI this summer, Weiler had a lot of experience in ocean research. She volunteered in labs back home and participated in several research cruises. Most of Weiler’s previous lab work involved marine chemistry, and she was able to incorporate those skills into her work at WHOI.
Weiler said squid movement is of particular interest with regard to ocean acidification because the organ squid use to detect their orientation in the water is vulnerable to ocean acidification. This organ, called a statocyst, is comparable to a human’s inner ear, which performs a similar function for us: enabling us to detect our position in space and maintain our balance. Inside the statocyst is a pebble-like structure called a statolith, which is made of calcium carbonate. The pressure of the statolith pressing at different places inside the statocyst, like a pebble falling on different spots inside a hollow ball as the ball rolls around, tells the squid its position.
Previous experiments in Mooney’s lab found that statoliths do not develop normally if the squid are kept in water with high acidity. Weiler’s job was to find out if that affected the squids’ ability to maintain their orientation and to maneuver through the water.
“When you look at the statoliths of squid that have been raised in higher levels of carbon dioxide, it is evident that they are damaged, so we’re trying to see if this anatomical change has behavioral effects as well,” Weiler said.
To test whether and in what ways the movements of young squid are affected by ocean acidification, Weiler developed squid eggs with varying concentrations of carbon dioxide, some high enough to cause damage to the statoliths (higher concentrations of CO2 produce a lower pH, or more acidity). Once the eggs hatched—an event affectionately known in Mooney’s lab as a “squidsplosion”—she monitored the babies’ swimming patterns. Cameras recorded the squid from different angles to generate three-dimensional plots of their movements. Weiler is now analyzing the results, looking mainly at the squids’ velocity and depth.
After Weiler completes her research this summer, she will go to the island of Moorea, near Tahiti, to work on an independent project through the fall. She hopes to make her career in the field of marine biology. “This is hands down what I want to do!” she said.
Weiler and her research were supported by The Seth Sprague Educational and Charitable Foundation Fund.