A University of Maryland scientist who published a paper this week concluding that ammonium-laden wastewater discharges from Sacramento are at the root of the Delta's ecological demise has been dismissed from a prestigious panel of scientists studying the decline.

Patricia Glibert, a respected ecologist, determined that increases in ammonium downstream of the Sacramento Regional County Sanitation District's sewage treatment plant fundamentally altered the kinds of plankton that thrive in the Delta, and that change rippled up the food web in ways that led to the decline of native fish.

Glibert was asked to resign Thursday from a panel assembled by the National Academy of Sciences because the paper laid down firm conclusions while the committee is still trying to work through the Delta's problems.

"Given how definitive the conclusions were this week and the fact that they were released publicly, we felt it would be inappropriate for her to be reviewing her own work," said William Kearney, spokesman for the National Academy of Sciences.

Glibert could not be immediately reached Friday. But her forced resignation prompted another member of the panel to resign.

Michael J. McGuire, a water treatment consultant and former assistant general manager at the Metropolitan Water District of Southern California, said some members of the committee are focused on water delivery operations as the cause of the Delta's problems. Glibert's departure, he said, will make it difficult to fully evaluate pollution and other problems.

"Given the fixed points of view of many of the remaining committee members and the stilling of an important alternative voice on the committee, I do not see how I can contribute to provide a meaningful contribution," McGuire wrote in his resignation letter.

"We will replace them with two or more committee members to make sure we have the necessary expertise and balance of scientific perspective to carry out the second phase of this study," Kearney said.

The panel started work in November in response to concerns that environmental regulations designed to halt the Delta's decline might be overly focused on cutting water supplies. In March, it released an initial report that found the rules appear to be scientifically justified, at least in concept.

In fall 2011, the committee is due to develop a more definitive report that is expected to discuss the relative importance of water deliveries, ammonium discharges and other environmental stresses on the Delta.

Mike Taugher covers the environment. Contact him at 925-943-8257.