The Coastal Dune Lakes of Eastern Australia

Abstract

Most lakes in siliceous dunes in eastern Australia originated through deflation and organic accumulation to form on perched watertables in otherwise porous sand. Salinity is low (<50 mg 1-1), Na+ and Cl- ions are dominant, Ca2+ and HCO3- ions are almost absent, and the water is acidic (pH <5·0) and humic. Many of the biota are distinctive, including a sparse, desmid-dominated phytoplankton, the limnetic copepod Calamoecia tasmanica, and a few other microcrustaceans, odonates, trichopterans, chironomids and fish. Planarians, rotifers, ostracods, amphipods and molluscs are rarely present. Biological communities tend to be simple so that the result of predator-prey interactions may be obvious. Energy pathways apparently rely on allochthonous organic matter. Community structure and function vary between lakes according to slight differences in physiographical position and hence water chemistry. Six types of dune lake are recognized at present, though more may exist in poorly known regions. Dune lakes are threatened by mining, mobile sand, cultural eutrophication, and exotic biota.