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Water Pollution at Topanga State Beach Baffles Scientists
February 21, 2013 -
Reprinted with permission from the website of County Supervisor Zev Yaroslavsky, where it originally appeared.
PHOTO BY ROSI DAGIT
Scientists from UCLA and Santa Monica Mountains Resource Conservation District take samples from the Topanga Lagoon.
It has been a mystery now for almost a decade: Whats polluting the water at Topanga State Beach?
Once regarded as one of the cleanest stretches of ocean in Los Angeles County, Topanga fell from grace around 2003, when high bacteria levels sank its water quality score on Heal the Bays annual Beach Report Card.
Although cleanup efforts were diligent, testing methods couldnt pinpoint the source of the problem. Theories abounded. Was it someones leaky septic system? Birds and coyotes? Illegal dumping upstream in Topanga Creek?
We thought it might be the old septic system at the public restrooms, says Rosi Dagit, senior conservation biologist for the Santa Monica Mountains Resource Conservation District. So that was redone and replaced with a state-of-the-art system.
Then we thought it might be the old septic systems in the rodeo grounds upstream from the lagoon, so those were removed, too.
But the problem remained. We kept taking out potential sources of bacteria, Dagit says, and the beach kept getting these high numbers. Consequently, even though other types of pollution are markedly low at Topanga, the beach has been more or less a regular on Heal the Bays official Beach Bummers 10-worst-beaches list.
Now Topanga Beach has become the focus of an in-depth study that will seek to finally nail down the reason behind the chronically high levels of total coliform, fecal coliform and enterococcus bacteria, which may make swimmers sick.
Piggybacking on a larger statewide look at beach pollution hotspots that began in 2010, the new, two-year look at Topanga, which began in November 2012, will sample water up to twice monthly from as many as 10 locations on Topanga State Beach and along the lower section of the creek that feeds the lagoon there. The samples then will be subjected to rigorous DNA testing.
The study also will examine the connection between tiny invertebrates and nutrient levels in the water, along with why the generally normal bacteria levels in the creek tend to spike when the water hits the lagoon and ocean, says Dagit. Therell also be an educational component, with opportunities for school children to visit the testing labs at UCLA and learn how to help keep Southern Californias water clean.
The added scrutinyexpected to cost $550,000 during the studys two yearsis being funded through an allocation from the office of Los Angeles County Supervisor Zev Yaroslavsky.
The Topanga effort is being jointly overseen by UCLA, which is a local lead on the statewide study, and the Resource Conservation District. Dagit, the countys point-person on the project, says the tests are complex and relatively new.
You have to collect the samples before sunlight hits the water, she says, because the sun makes bacteria go crazy. So weve been getting up at night and going down to the water before sun-up. Our last sampling was December 19, and let me tell you, it was cold.
The tests also are expensiveabout $200 per half-gallon water samplebut have come down markedly in cost over the past few years. Scientists are enthusiastic about the studys prospects.
Its like DNA fingerprinting of bacteria, says Dagit. Well be able to find out not only whether the source is human or non-human, but if its non-human, whether its from gulls, dogs, coyotes or horses and whether it came from a direct deposit on the beach, or from gray water or a septic system.
Thats important, she says, because bacteria from a natural source, such as wildlife, requires a different set of solutions than does bacteria from the feces of pets and humans.
Suppose those bacteria levels are because of a lot of gulls roosting at Topanga Lagoon, Dagit says. We dont want people swimming in water with high bacterial levels, but we dont want to get rid of the gulls. Dagit says that by this time next year, scientists should have many more clues to the mystery at Topanga Beach. It should be pretty amazing, she says. We havent really had the technology to do this kind of study until now.
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