Pink dye in Los Peñasquitos Lagoon
Pink dye is released Friday in Los Peñasquitos Lagoon. Photo by Erik Jepsen/UC San Diego

Coastal waters off Torrey Pines Beach are turning pink in a series of experiments to see how how fresh water plumes effect the ocean.

The first of three releases of environmentally safe dye in the Los Peñasquitos Lagoon took place Friday, and two more are planned through early February. All dye releases will occur during ebb tide when the water level is falling.

The research, led by Scripps Institution of Oceanography and the University of Washington, seeks 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. 

“I’m excited because this research hasn’t been done before and it’s a really unique experiment,” said Scripps coastal oceanographer Sarah Giddings, who is leading the study. “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.”

Researchers will track the fluorescent pink dye from land, sea, and sky using a variety of instruments including drones, sensors affixed to poles in the sand in the river mouth and surfzone, and a jet ski.

The Los Peñasquitos Lagoon was chosen as the study site because it is a “prime example” of a small river plume discharging into the surfzone along a relatively uniform stretch of coastline.

The study, which is funded by the National Science Foundation, is expected to provide crucial data for quantifying the spread of sediment, pollutants, larvae, and other important material in the near-shore environment.

Scripps scientists have successfully used pink dye to conduct other near-shore experiments, including an international study tracking beach pollution dynamics near the U.S-Mexico border in 2015, and earlier work at Imperial Beach.

Chris Jennewein is Editor & Publisher of Times of San Diego.