By Janet Raloff
Several U.S. research teams report reproductive problems in Gulf Coast fish that periodically encounter oxygen at concentrations as low as those in so-called dead zones (SN: 6/5/04, p. 360: Dead Waters). Two teams have also turned up gene changes that may underlie the diminished, less productive gonads found in these fish.
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Christie A. Landry of Southeastern Louisiana University in Hammond and her colleagues studied Gulf killifish, a type of minnow, in three bays where oxygen concentrations vary with the tide. In some cases, oxygen fluctuated only within healthy concentrations of 6 to 8 parts per million (ppm). Elsewhere, concentrations bottomed out for 3 hours a day at oxygen-starved, or hypoxic, values of 1 to 2 ppm. Last month in New Orleans at the E.Hormone conference on hormone-mimicking conditions in the environment, the researchers linked that hypoxia to reproductive changes.