Seasonal hypoxia, when dissolved oxygen concentrations in water drop below 2 milligrams per liter, is a normal summer occurrence in estuaries. Over the past 20 years, however, pollution has increased the severity and frequency of hypoxia in waters worldwide. That trend could put a crimp in the reproductive capacity of coastal fish, new research shows.
Earlier laboratory studies indicated that in species that can survive hypoxia, reproduction shuts down (SN: 3/1/03, p. 132). Peter Thomas and his colleagues at the University of Texas Marine Science Institute in Port Aransas have now shown that some Atlantic croakers (Micropogonias undulatus) in the Gulf of Mexico have underdeveloped sperm and eggs. The fish were living in parts of Florida's Pensacola Bay that are hypoxic for extended periods each year.