Santa Monica’s waves will run pink during UCLA water quality test

Visitors to Santa Monica Beach may notice the ocean waves turning pink September 15, 22-24 and 30 near the breakwater and pier because of a temporary, non-toxic dye used to study water quality. Researchers from the UCLA Samueli School of Engineering will release the dye in collaboration with The Bay Foundation. The fluorescent Rhodamine Water Tracer dye, which has been used by researchers for many years to understand water movement, will disperse naturally and pose no risk to people, animals or vegetation.

The project builds on a 2024 experiment by the UCLA Coastal Flood Lab and The Bay Foundation, continuing efforts to study how the Santa Monica Breakwater influences ocean circulation and contributes to poor water quality.

Constructed in 1934 to create the Santa Monica Yacht Harbor, the breakwater reduced wave energy and allowed boats to dock in calmer waters. Over time, storms damaged the structure, and by the mid-1980s, it had been reduced to its current height, making it no longer functional as a marina. The rocky breakwater remnants offshore of the pier are visible from the beach, especially at low tide.

"Although the breakwater was badly damaged and the elevation reduced, it still substantially impacts the coastal hydrodynamics and surrounding environment," said Timu Gallien, an associate professor of civil and environmental engineering at UCLA Samueli and the study's principal investigator. "For example, the breakwater protects the beach from large waves, keeping the beach wider that it would naturally be."

The water containing the dye will carry the passive tracer wherever the current leads. If wave conditions are favorable, researchers will release the dye near the breakwater and use monitors to track its movement.

"By following where the dye goes, we will better understand how the breakwater changes the environment around it, providing insight into Santa Monica Beach's poor water quality," said Isabella Arzeno Soltero, an assistant professor of civil and environmental engineering at UCLA Samueli and the study's co-investigator.

Funded by The Bay Foundation, the research team includes project leads Bernabe Gomez, a postdoctoral scholar who will perform the numerical wave modeling, and Gallien's doctoral student Gabi Carr, who will investigate the eDNA characterization of the breakwater. Alejandro Angel, a Ph.D. student in Gallien's research group, will conduct circulation modeling while Arzeno-Soltero's doctoral student Eber Reyes will be involved in data analysis.

"We are proud to support UCLA in this important research," said Tom Ford, CEO of The Bay Foundation and director of the Santa Monica Bay National Estuary Program. "The findings will help guide efforts to protect and restore this vital coastal ecosystem."

Established in 1990, The Bay Foundation is a nonprofit environmental organization dedicated to restoring and enhancing Santa Monica Bay and its surrounding coastal waters. Its mission is to improve water quality, conserve and rehabilitate natural resources, and protect the Bay's benefits and values through collaborative actions and partnerships.

The dye releases have been reviewed and approved by the city of Santa Monica, the California Coastal Commission and the U.S. Army Corps of Engineers. Researchers will be at the site during the experiments to share informational brochures and answer questions from the community.