Estuary Contaminants Impact Stripped Bass Offspring, Implications for Public Drinking Water Consumption
(Beyond Pesticides, December 15, 2008) Striped bass in the San Francisco Estuary are contaminated before birth with a toxic mix of pesticides, industrial chemicals and flame retardants that their mothers acquire from estuary waters and food sources and pass on to their eggs, according to a new study by University of California Davis researchers. Using new analytical techniques, the study, “Maternal Transfer of Xenobiotics and Effects on Larval Striped Bass in the San Francisco Estuary” finds offspring of estuary fish have underdeveloped brains, inadequate energy supplies and dysfunctional livers. They grow slower and are smaller than offspring of hatchery fish raised in clean water. The findings have implications far beyond fish, because the estuary is the water source for two-thirds of the people and most of the farms in California.
“This is one of the first studies examining the effects of real-world contaminant mixtures on growth and development in wildlife,” said study lead author David Ostrach, a research scientist at the UC Davis Center for Watershed Sciences. “If the fish living in this water are not healthy and are passing on contaminants to their young, what is happening to the people who use the water, are exposed to the same chemicals or eat the fish?…We should be asking hard questions about the nature and source of these contaminants, as well as acting to stop the ongoing pollution and mitigate these current problems.”
The new study, published online by the journal Proceedings of the National Academy of Sciences, is one of a series of reports by UC Davis researchers on investigations they began in 1988. Their goal is to better understand the reasons for plummeting fish populations in the estuary, an enormous California region that includes the Sacramento-San Joaquin River Delta and San Francisco Bay.
The estuary is one of the world’s most important water supplies for urban use and agriculture, and is also one of the most contaminated aquatic ecosystems. The ominous decline in estuary populations of striped bass, delta smelt, longfin smelt and threadfin shad, named the “pelagic organism decline,” or POD, by the region’s environmental scientists, was first reported at the turn of the century. The UC Davis lab is part of the multi-agency POD research team and charged with understanding contaminant effects and other environmental stressors on the entire life cycle of striped bass. The new study details how the research team caught gravid female striped bass in the Upper Sacramento River, then compared the river fishes’ eggs and hatchlings (larvae) to offspring of identical but uncontaminated fish raised in a hatchery.
Studies of striped bass are useful because, first, they are a key indicator of San Francisco Estuary ecosystem health and, second, because contaminant levels and effects in the fish could predict the same in people. In the river-caught fishes’ offspring, the UC Davis researchers found harmful amounts of PBDEs, PCBs and 16 pesticides, including commonly used agricultural chemicals such as chlorpyrifos, and others banned decades ago, such as dieldren and DDT.
The compounds identified are known to cause myriad problems in both young and adult organisms, including skeletal and organ deformities and dysfunction; changes in hormone function (endocrine disruption); and changes in behavior. Some of the effects are permanent. Furthermore, according to the researchers, when the compounds are combined, the effects can be increased by several orders of magnitude.
For more information on how water contaminated by pesticides impacts wildlife and public health, see Beyond Pesticides’ Threatened Waters program page.