Striped bass in the San Francisco Estuary are contaminated beforebirth with a toxic mix of pesticides, industrial chemicals and flameretardants that their mothers acquire from estuary waters and foodsources and pass on to their eggs, say UC Davis researchers.
Using new analytical techniques, the researchers found that offspringof estuary fish had underdeveloped brains, inadequate energy suppliesand dysfunctional livers. They grew slower and were smaller thanoffspring of hatchery fish raised in clean water.
"This is one of the first studies examining the effects of real-worldcontaminant mixtures on growth and development in wildlife," saidstudy lead author David Ostrach, a research scientist at the UC DavisCenter for Watershed Sciences. He said the findings have implicationsfar beyond fish, because the estuary is the water source fortwo-thirds of the people and most of the farms in California.
"If the fish living in this water are not healthy and are passing oncontaminants to their young, what is happening to the people who usethe water, are exposed to the same chemicals or eat the fish?"Ostrach said.
"We should be asking hard questions about the nature and source ofthese contaminants, as well as acting to stop the ongoing pollutionand mitigate these current problems."
The new study, published online Nov. 24 by the journal Proceedings ofthe National Academy of Sciences, is one of a series of reports byOstrach and UC Davis colleagues on investigations they began in 1988.Their goal is to better understand the reasons for plummeting fishpopulations in the estuary, an enormous California region thatincludes the Sacramento-San Joaquin River Delta and San Francisco Bay.
The estuary is one of the world's most important water supplies forurban use and agriculture, and is also one of the most contaminatedaquatic ecosystems.
The ominous decline in estuary populations of striped bass, deltasmelt, longfin smelt and threadfin shad, named the "pelagic organismdecline," or POD, by the region's environmental scientists, was firstreported at the turn of the century and has continued to worsenthrough 2007.
Ostrach's lab at UC Davis is part of the multi-agency POD researchteam and charged with understanding contaminant effects and otherenvironmental stressors on the entire life cycle of striped bass.
Studies of striped bass are useful because, first, they are a keyindicator of San Francisco Estuary ecosystem health and, second,because contaminant levels and effects in the fish could predict thesame in people. For example, one of the contaminants found in thefish in this study, PDBEs, have been found in Bay Area women's breastmilk at levels 100 times those measured in women elsewhere in theworld.
The new study details how Ostrach and his team caught gravid femalestriped bass in the Upper Sacramento River, then compared the riverfishes' eggs and hatchlings (larvae) to offspring of identical butuncontaminated fish raised in a hatchery.
In the river-caught fishes' offspring, the UC Davis researchers foundharmful amounts of PBDEs, PCBs and 16 pesticides.
PBDEs (polybrominated diphenyl ethers) are widely used flameretardants; PCBs (polychlorinated biphenyls) are chemicals once usedin making a range of products, from paper goods to electrictransformers; and the pesticides detected include some currentlywidely used in agriculture, such as chlorpyrifos and dieldren, andothers banned decades ago, such as DDT.
These compounds are known to cause myriad problems in both young andadult organisms, including skeletal and organ deformities anddysfunction; changes in hormone function (endocrine disruption); andchanges in behavior. Some of the effects are permanent. Furthermore,Ostrach said, when the compounds are combined, the effects can beincreased by several orders of magnitude.
Source: University of California - Davis