Synchronous Response of Hydrophobic Chemicals in Herring Gull Eggs from the Great Lakes

Abstract

Herring gull eggs from Great Lakes nesting sites exhibit short-term changes in hydrophobic chemical concentrations that are synchronized within and between Great Lakes. At one Lake Ontario site, for example, short-term deviations from long-term trends for PCBs, DDE, mirex, hexachlorobenzene, and dieldrin in gull eggs tend to correlate significantly with each other, with these chemicals at another site in Lake Ontario, and with gull egg chemicals from Lakes Superior, Huron, and Erie. Similar comparisons made for other Great Lakes are also significantly nonrandom. This synchrony indicates that some large-scale force-here proposed to be weather patterns-controls short-term patterns of hydrophobic chemical concentrations in gull eggs acrossthe Great Lakes. Among eight alternative hypotheses considered, the data are least inconsistent with the following mechanism : warm spring weather conducive to phytoplankton growth produces relatively uncontaminated phytoplankton, which in turn produce less contaminated food for the gulls during the critical period of egg yolk formation (and vice versa for cold spring weather).