Lago Santa Margarita Update


A small number of carp, catfish and mosquito fish are currently thriving in Lago Santa Margarita along with an abundance of turtles, crawdads and birds. However, Golden Algae is still a very real threat to fish, not only Lago Santa Margarita but to the neighboring Lakes in and around Southern California.

Golden alga (Prymnesium parvum) is a single-celled organism that lives in water. It occurs worldwide, primarily in coastal waters, but it is also found in rivers and lakes. It doesn't always cause problems, but when it "blooms," (enters a phase of rapid growth and reproduction) this algae can produce toxins that cause fish kills. The toxins affect organisms that have gills: all types of fish, freshwater mussels and clams, and the gill-breathing juvenile stage of frogs and other amphibians.

A golden algae fish kill may last for days, weeks, or months. Sometimes only a portion of a lake is affected, but the location can change from one day to the next. Blooms are more likely to occur in cold weather, and sometimes taper off as the water warms and other species of algae become more active — but not always. An extended kill can have long-term effects on a fishery and cause economic hardship for parks and businesses that serve recreational anglers.

SAMLARC has been battling Golden Algae for more than two years with the last fish kill occurring in November 2015. Since that time, various treatments have been tried with no long-term success. Until Golden Algae can be managed, the Board of Directors has elected not to re-stock the Lake and risk another fish kill.

The Lake water is tested on a monthly basis to measure the levels of Golden Algae, Blue Green Algae and other microorganisms living in the Lake. For the most part, the levels of harmful Golden Algae have been low or non-existent within the Rancho Santa Margarita Lake when recently tested. Golden Algae levels are likely low at this time because of winter rainfall in Southern California and the summer heat warming the water; however, the Lake is still at risk of a Golden Algae bloom.

Golden algae-related fish kills have occurred in inland waters with high salt or mineral content. Because Lago Santa Margarita was not constructed with the ability to turn over water, the salt and mineral content have increased over the years to a level that is believed to contribute to the success of Golden Algae lying dormant and blooming when the conditions are optimal.

Recently, SAMLARC reached out to Santa Margarita Water District (SMWD) requesting a partnership to address the high salt and mineral content in the Lake. SMWD is partnering with SAMLARC in the development of a project that will convert the Lake from a closed system to an open, “flow-through” system. This will be accomplished by recycling the water in the Lake for use as irrigation water in landscaped areas around the Lake. The water used for irrigation will then be replaced with fresh water. The continual flow of fresh water into the Lake will maintain healthier water quality levels which is intended to keep the Golden Algae levels and toxins under control.

The Board of Directors recently approved a proposal with an experienced engineer to design a system to convert Lago Santa Margarita from a closed system to a “flow-through” system. The design process for Lago Santa Margarita has just begun, and the design will take approximately 9-12 weeks to be completed. At the same time, SAMLARC is working with landscape irrigation consultants to obtain designs to link all of the irrigation zones that surround the Lake. Linking the irrigation zones will maximize the water usage for irrigation around the Lake and keep a recurrent flow of fresh water going back into the Lake.

While the design and construction process will take time to complete, other animals and fish in the Lake continue to thrive in their natural home. Please be sure to check the SAMLARC website for updates on the health and revitalization of the Lake as more information becomes available.


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22342A Avenida Empresa, Suite 102A, Rancho Santa Margarita, CA 92688

(949) 709-0010

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