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Wednesday, May 18, 2011

Preliminary Results of USGS Study Indicates Birds Are Bacteria Source

• Civic Center Area’s Septic Systems Appear to Be Functioning Adequately According to Scientists

BY SUZANNE GULDIMANN

It apparently will not impact the Regional Water Quality Control Board’s mandate for Civic Center sewers, or a State Parks plan to drain, dredge and reconstruct the western portion of the Malibu Lagoon, but the preliminary results of an extensive United States Geologic Survey study indicate that Malibu’s Civic Center-area septic systems are successfully removing human-specific bacteria and are apparently not to blame for lagoon contamination.
“Fecal indicator bacteria, or FIB, sometimes found in the Malibu Lagoon and the near-shore ocean water, may not be the result of human waste contamination,” states a summery of the preliminary results of a new USGS study, released this week.
The announcement rocked the audience when a preview of the study was presented to the Malibu City Council last month at a meeting packed with lagoon project opponents. The official report was released this week with extensive analysis of the research collected by a USGS team headed by research hydrologist John Izbicki.
“The concern that FIB might be coming from residential onsite wastewater treatment systems prompted the City of Malibu to request a USGS study to discover the source of the occasional presence of FIB,” the press release on the study states. “Tests show that FIB concentrations routinely exceed U.S. Environmental Protection Agency public health standards for marine recreational water in Malibu Lagoon and occasionally exceed those standards at several Malibu beaches.”
“To reach sensitive receiving waters, such as Malibu Lagoon or the near-shore ocean, treated wastewater must first move through the underlying shallow groundwater. The absence of FIB is consistent with changes in the abundance and type of microorganisms indicated by preliminary analysis of genetic data that would be expected from a combination of filtration, sorption, death, predation, and other factors,” the findings state.
“Data collected for this study indicate that fecal indicator bacteria and human-specific bacteroides, an indication of human fecal material, are high in samples from within onsite wastewater-treatment systems; however, they are generally absent in samples from wells, even though many of the sampled wells contain water having a wastewater history,” wrote Izbicki.
According to the preliminary results of the study, “scientists suspect possible sources of FIB to the ocean are kelp accumulated on the beach, discharge from Malibu Lagoon to the ocean, or movement of water from the lagoon through the sand berm separating the lagoon from the ocean.” More specific results are anticipated once the study is complete, the press release states.
The study, which involved sample collection from numerous test sites, “utilized a combination of isotopic, microbiological, and chemical techniques,” the report states.
“Isotopic techniques identified the source of water and identified when groundwater discharge to the lagoon and ocean were occurring. Microbiological techniques used DNA and other biogeochemical compounds to determine if organisms associated with human waste were present in groundwater, Malibu Lagoon, and the near-shore ocean. Chemical techniques used compounds associated with human use such as cholesterol, cosmetics, and plasticizers to determine if water had a history of human use.
Study findings also appear to indicate that the berm that separates the lagoon from the open ocean during the dry season may be more permeable than previously realized, allowing contamination to leach through the barrier even when the breach is closed.
“Direct discharge from Malibu Lagoon to the ocean during the April sample period was a source of FIB to the ocean, and movement of water from the lagoon through the berm separating the lagoon from the ocean was a source of FIB to the near-shore ocean during the July sample period at low tide.” the document states.
“Enterococci concentrations in Malibu Lagoon commonly exceeded the USEPA single sample standard for marine recreational water during the July (dry season) and April (wet season) sample periods. Enterococci concentrations decreased during the July sampling period as high tides and large waves caused ocean water to flow over the berm into the lagoon. During this time, enterococci concentrations decreased to low values during the mid-afternoon, possibly as a result of photoinactivation by ultraviolet radiation in sunlight. In contrast, during the April sampling period, enterococci concentrations in the lagoon varied with the daily tidal cycles, as ocean water having low FIB concentrations entered the lagoon during high tide and water having high FIB concentrations exited the lagoon during low tide six hours later.
The preliminary finds warn that “data collected as part of this study need further interpretation before final conclusions can be drawn.
“In particular, statistical analysis of genetic data (T-RFLP, Phylochip), molecular data (PLFA), and chemical data needs to be completed to fully understand how these complex data sets relate to FIB occurrence and sources in this complex hydrologic setting.”
“Enterococci concentrations were lower at Surfrider Beach and Malibu Colony Beach than in Malibu Lagoon,” the study finds. “In general, enterococci concentrations were higher at Surfrider Beach than at Malibu Colony Beach, especially during low tide in April when water from the lagoon discharged directly to the ocean near Surfrider Beach. Enterococcus concentrations at Malibu Colony Beach were higher at high tide in the summer than at low tide when groundwater discharge was greater.”
“Each year, over 550 million people visit California’s public beaches,” the press release concludes.
“To protect beach-goers from exposure to waterborne disease, California state law requires water-quality monitoring for FIB, such as enterococci and Escherichia coli, at beaches having more than 50,000 yearly visitors.
“FIB are used to assess the microbiological quality of water because, although not typically disease causing, they are correlated with the occurrence of certain waterborne diseases.”
The complete preliminary report is available online at http://pubs.usgs.gov/of/2011/1091

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