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.
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.