Why did the water at beaches in San Diego, California turn pink?

What would you think if you went for a walk at the beach and saw pink-tinted water like this? Recently, beachgoers were shocked by the pink water in San Diego, California.

Photo: Scripps UC San Diego

The most typical reaction would be to think that a toxic spill of some kind must have polluted the water. However, that wasn't the case; the water at the beach was pink due to a science experiment.

Photo: Scripps UC San Diego

During January and February 2023, researchers from UC San Diego's Scripps Institution of Oceanography and the University of Washington dyed the waters of San Diego's beaches fluorescent pink.

Photo: Scripps UC San Diego

The dyed water was released into Los Pensaquitos lagoon to see how freshwater flows interact with areas where waves break. The result was that the coastal waters between Torry Pines State Beach and the San Diego Nature Reserve turned a bizarre shade of Pepto Bismal pink.

Photo: Scripps UC San Diego

The University of California in San Diego  reassured the citizens worried about the pink water that the dye used was environmentally safe and had the approval of the authorities in the area.

Photo: Instagram - Scripps UC San Diego

The objective of this experiment, summarizing in a simple way, is to monitor the interactions that fresh water has with the sea waves that break on the coast.

Photo: Scripps UC San Diego

Those who created the experiment hope "to understand how plumes of more buoyant, fresher water interact with the denser, saltier and often colder near-shore ocean environment, particularly as the plumes encounter breaking waves," according to The Times of San Diego.

Photo: Scripps UC San Diego

To achieve this, they use this striking pink pigment that makes it easier to trace freshwater plumes, making them much more visible.

Photo: Instagram - Scripps UC San Diego

"Rivers and estuaries play an important role in delivering freshwater and materials such as sediments and contaminants to the coastal ocean," as shared on the Scripps Instagram account.

Photo: Instagram - Scripps UC San Diego

"...but little is known about how these plumes of more buoyant, fresher water interact with the denser, saltier and often colder nearshore ocean environment, particularly as the plumes encounter breaking waves."

Photo: Scripps UC San Diego

To track the plumes, the research team used drones, ground sensors and also submerged sensors that are capable of measuring the height of the waves and the temperature of the water.

Photo: Instagram - Scripps UC San Diego

Sarah Giddings, an oceanographer at UC San Diego's Scripps Institution of Oceanography and director of the project, could not hide her delight at the experiment her team carried out.

Photo: Scripps UC San Diego

The Times of San Diego spoke with Scripps who said, “I’m excited because this research hasn’t been done before and it’s a really unique experiment."

Photo: Instagram - Scripps UC San Diego

"We will combine results from this experiment with an older field study and computer models that will allow us to make progress on understanding how these plumes spread,” Giddings added.

Photo: Scripps UC San Diego

To ensure that the dye is released from the lagoon into the ocean, pink dye discharges are always released at low tide.

Photo: Instagram - Scripps UC San Diego

The dye is not toxic, nor does it represent a danger to humans, wildlife or the environment, but it does allow it the plumes of freshwater to be tracked for 24 hours. However, after that time, it leaves no trace or sequelae in the area of release.

Photo: Scripps UC San Diego