Human waste ammonia likely cause of California fish kills

After years of searching high and low for a culprit in the collapse of Delta fish populations, scientists are learning the problem may lie right under their noses.

The likely fish killer is ammonia, a common byproduct of human urine and feces.

Sacramento's regional sewage treatment plant is the largest single source of ammonia in the Delta. It discharges treated wastewater from nearly 1.4 million people into the Sacramento River near Freeport – without removing ammonia.

Two recent studies by Richard Dugdale, an oceanographer at San Francisco State University, show that ammonia disrupts the food chain in the Sacramento-San Joaquin Delta.

The discovery, if it holds up to further scientific review, reveals how just one factor can tilt the Delta's complex ecological balance. It also illustrates how fixing the Delta will be a costly task for many California residents who mistakenly assume their lives are not connected to the estuary.

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