Development of Eighteen Mile Swamp, North Stradbroke Island: a palaeolimnological study

Abstract

Relatively little is known about the formation and stability of coastal wetlands in Australia and less still is understood about the formation of fresh groundwater fed wetlands in coastal environments. Eighteen Mile Swamp is a shallow, groundwater fed, freshwater coastal wetland stretching almost the entire length of the eastern side of North Stradbroke Island, south east Queensland. In order to determine the timing and nature of Eighteen Mile Swamp’s formation and evolution, and to examine the response of the wetland to climate, we examined the diatom record from a 210 cm sediment core. The approximately 650 year record was taken from an open water pool on the western margin of the swamp, approximately half way along its north-south axis. Diatom assemblages and sediment analysis were used to reconstruct the wetland’s history and indicate that Eighteen Mile Swamp evolved from an estuarine system to a freshwater acidic wetland approximately 420 years ago. From this time onwards, the diatom record demonstrates very little variation, indicating an apparent resistance to climatic variability and human interference.