My fears grew as we motored around the west tip of Black Rock. Two Vietnamese families were busy with nets, scooping up hundreds of tilapia, gasping for air, along the shore. Their trucks were loaded down with multiple ice chests already full of tilapia. Two young men labored to lift a stinger of black tilapia into one of the trucks. It was so large that from a distance it looked like they were hefting a body bag.
Motoring south to the end of Lack Road Dike near the power plant, the sun was coming up and the water was pea soup green and my worst fears were confirmed. Triggered by the high winds the day before, the south end of the Salton Sea had suffered from a massive algae bloom. A fish die-off was in progress before our very eyes. We fished the rest of the day, looking for oxygen-laden brown water but where we found it the fish were not biting. By afternoon, dead croakers and tilapia floated on the water as far as we could see.
For a hundred years the Salton Sea has been a repository for agricultural drainwater and city waste discharges, including those of Mexicali. Because it's below sea level, what flows to the Salton Sea can never leave. Only the water evaporates. The salts are left behind and make the sea saltier with each passing year. As the water evaporates, nitrates and phosphates, that act as fertilizers for the algae, become more concentrated. Some of the nitrates may disappear into the atmosphere as ammonia gas, but every bit of phosphate that ever entered the Salton Sea remains dissolved in the water or concentrated in the bottom sediment.
Water from the Salton Sea is a very potent growing medium for the different algae and plankton that live in the sea. In fact it's way too potent and that's what feeds a chain reaction that culminates in a fish die-off from oxygen depleted water. This cycle repeats itself many times a year in localized areas and over large parts of the Salton Sea.
Algae and plankton are plants that give off oxygen, which fish breathe through their gills. Fish give off carbon dioxide, which in-turn, is used by the plants to live. This whole process creates a precarious balance between the fish and plants in the Salton Sea. A chain reaction is triggered when high winds stir up the bottom sediment and a big jolt of fertilizer is added to the already over-fertilized water. When this happens, the plants begin growing at runaway speed.
The result is a temporary high spike in oxygen production, which is used by the fish. The fish, however, can't produce enough carbon dioxide for the rapidly increasing amount of algae and plankton in the water. The plants, after showing explosive growth, find themselves without carbon dioxide and die just as quickly. When they die, the fish no longer have a source of oxygen and they, too, perish soon after.
To further complicate the problem, high salt content, as well as high water temperatures, decrease the amount of dissolved oxygen the water can hold. It gets even worse because the process that breaks down the dead algae, plankton and fish uses up all the remaining oxygen.
How long it takes for the water to return to a point where fish can survive depends on temperature, wind and currents that move the good water around, mixing it with the dead water.
Steve Horvitz, superintendent of the Salton Sea State Recreation Area at the northeast end of the Salton Sea, has written one of the most comprehensive explanations about the misunderstood Salton Sea I have ever read. It's called "Salton Sea 101" and can be found on the Internet at www.saltonseainfo.com. It also can be purchased from the bookstore at the Salton Sea State Recreation Area. The phone number for the Salton Sea State Recreation Area is (760) 393-3059. Be sure to get a copy. You won't regret it.
Outdoor Tales writer, Al Kalin, can be reached on the Internet at firstname.lastname@example.org