Is the dye harmful?
The dye used is Rhodamine WT. This chemical is not considered hazardous by the 2012 OSHA Hazard Communication Standard (29 CFR 1910.1200). The product contains no substances which at their given concentration, are considered to be hazardous to health. In fact, this product is approved for use by the EPA and FDA in drinking water studies!
Do beach closures relate to this study?
No, the beach was closed due to a rainfall event, which led to contaminated water flowing into the Tijuana Estuary and storm drains and onto the coast. If you still see beach closure signs, please pay attention to them and heed their warnings! We are in direct contact with the folks that take the water samples and are operating only in regions believed to be safe, nevertheless, extra precautions are always in order as we are taking ourselves!
If I cannot see it, is it there?
Yes, just like pollutants can be present without seeing or smelling them, Rhodamine dye can be present at concentrations beneath which it can be seen by the naked eye (the difference is that it is not a pollutant!)
How do you measure it?
The dye is a fluorescent dye, meaning that when a certain wavelength of light is shone on it, it emits at a different wavelength. Our instruments shine a green light on the water and detect the red light emitted. The amount of red light emitted is directly proportional to the concentration of the dye, which we have calibrated with lab samples.
What else are you measuring?
Water currents (speed and direction), temperature, salinity, and turbidity (how cloudy is the water due to things like sediment). We have surfzone based instrumentation, moorings (instruments sitting on the seafloor) offshore, boats, jet skis, a plane, and an underwater autonomous vehicle sampling!
What happened during the first dye release?
In the first dye release we measured dye in the surfzone at least up to Silver Strand due to southerly swell driving currents toward the north in the surfzone. However dye that was ejected offshore went south, we think due to strong winds and a bathymetric feature near the IB pier. As a result, for the second release, ejected dye north of the IB pier.
What happened during the second dye release?
Strong southerly swell drove strong currents towards the north and the dye shot up the coast. At first it was confined to the surfzone, after which it was confined to an alongshore band just outside of the surfzone. By the second day, dye was all the way up to the entrance to San Diego Bay (but in very low concentrations). Further south it was not near the surface, but it was found near the bottom! Very exciting data that we are looking forward to diving into.
Where is the 3rd dye release?
The third and last dye release will occur near the Tijuana Estuary river mouth. Offshore conditions are mixed and the bathymetry is complex so we are interested to see what happens!