The Loxahatchee River estuary empties into the Atlantic Ocean at Jupiter Inlet in southeastern Florida (fig. 1A). Although relatively small, the estuary is important for its esthetic value and for its sport fishing, boating, recreation, tourism, and prime residential development. In recent years, the condition of the estuary has become of concern to many citizens and agencies of the State. In response to this concern, the U.S. Geological Survey planned and carried out an in-depth environmental investigation. The events that led to the investigation and objectives of the investigation are outlined in a recent U.S. Geological Survey report by McPherson an Sabanskas (1980).