Introduction The Fourth Symposium on Sediment/Water Interactions was held in Melbourne, Australia, February 16-20th, 1987. The previous three symposia were held in Amsterdam, Kingston (Ontario), and Geneva, In keeping with the approach established in Geneva, contributions addressed sediment/water interactions related to both fresh and salt water conditions. More than 160 papers were given in Melbourne, including more than 20 poster presentations, and collected Abstracts are available from Dr. B. T. Hart. A total of 51 papers, subsequently, have been published as proceedings of the Melbourne Symposium; 45 of these appear in this issue of Hydrobiologia. A further six appeared earlier as a selection of papers in J. Environ. Geol. and Water Science (1988, issue # 1); these six papers appear in abstract form, only, in the present pUblication. Although concerned with the global environment, the International Association for Sediment Water Science attempts to ensure that there is a genuine opportunity for participants to focus on regional issues throughout the world and, in particular, to provide a local forum for their presentation. The Melbourne meeting was particularly successful in achieving this objective, and Australasia was well represented by about 36 percent of the contributors. About 27 percent were from Europe, 17 percent from North America, 7 percent from China and Japan, 7 percent from Southeast Asia and India, and about 6 percent came from other areas. In all, 25 countries were represented.

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Water and water science management.- Social choice, risk and determinism in water quality management.- Problems of organization in the science, politics and management of water.- Habitat changes.- Successional changes in habitat caused by sedimentation in navigation pools.- The effect of low water levels on the water quality of Lake Biwa, Japan.- Sediment dynamics, transport and deposition, and distributions.- The entrainment of sediments by the turbulent flow of water.- Hydro-sedimentology of the Johnstone River estuary, Australia.- Resuspension, ephemeral mud blankets and nitrogen cycling in Laholmsbukten, southeast Kattegat.- Sediment transport in an inland river in north Queensland.- Dynamic characteristics under low flow conditions in the Wakool River, New South Wales.- Sediment dispersion: part I, fine sediments and the significance of the silt/clay ratio.- Sediment dispersion: part II, characterization by size of sand fraction and percent mud.- The particle size characteristics of fluvial suspended sediment: an overview.- Contaminant accumulation, distributions, geochemistry and mineralogy.- Ionic alkyllead compounds in environmental water and sediments.- A study on heavy metal partitioning in sediments from Poyang Lake, China.- An environmental investigation of a marine coastal area: Gulf of Gaeta (Tyrrhenian Sea).- Variability of the heavy metal content of flood deposits (Abstract only).- Heavy metals in eelgrass (Zostera marina L.) during growth and decomposition.- Mercury pollution in Tokuyama Bay, Japan.- Distribution of nutrients, trace elements, PAHs and radionuclides in sediment cores from Lake Varese, Italy.- Nickel sorption and speciation in a marine environment.- The determination of heavy metals in water, suspended materials and sediments from the Langat River, Malaysia.- Trace elements in suspended particulate matter from the Yarra River, Australia.- Geochemical characteristics of heavy metals in the Xiangjiang River, China.- Material cycling.- Importance of sediments in understanding nutrient cyclings in lakes.- Characteristics of settling matter and its role in nutrient cycles in a deep oligotrophic lake.- Trace metal dynamics in a seasonally anoxic lake (Abstract only).- Nutrient remobilisation at the Tiber River mouth, Italy.- Use of radionuclides in the study of contaminant cycling processes.- Seasonal variations in the loosely sorbed phosphorus fraction of the sediment of a shallow and hypereutrophic lake (Abstract only).- Coupling of strontium and calcium cycles in Lake Constance, Switzerland.- Acid rain and lake acidification.- Acid rain and its effects on sediments in lakes and streams.- Concentrations and distribution of Fe, Zn and Cu in tissues of the white sucker (Catostomus commersoni) in relation to elevated levels of metals and low pH.- Microbially mediated reactions and contaminant effects on micbiota.- Microorganisms and the aquatic environment.- Accumulation of poly-?-hydroxybutyrate in a methane-enriched, halogenated, hydrocarbon-degrading soil column: implications for microbial community structure and nutritional status.- Bioavailability and toxic effects.- Can we determine the biological availability of sediment-bound trace elements?.- Sediment toxicity testing in two areas of concern of the Laurentian Great Lakes : Toronto (Ontario) 397 and Toledo (Ohio) Harbours.- Toxicity of metal polluted sediments to Daphnia magna and Tubifex tubifex.- Manipulation and disposal techniques.- Nitrate enhancement of nitrification depth in sediment/water microcosms (Abstract only).- Ceramic processing of polluted dredged mud.- Modelling.- A simulation of the process of sedimentation of suspended solids in the Yoshii River estuary, Japan.- The transport of fine-grained sediments in shallow waters (Abstract only).- Methods and analytical techniques.- Uncertainty in description of sediment chemical composition.- Study of metal sorption/desorption processes on competing sediment components with a multi-chamber device (Abstract only).- Sediment sampling evaluated with a new weighting function and index of reliability.- The use of turbidity in suspended sediment research.- Sediment trap assemblages: a methodological description.- Bioavailable metal uptake rate in urban stormwater determined by dialysis with receiving resins.- A sensitive screening bioassay technique for the toxicological assessment of small quantities of contaminated bottom or suspended sediments.- The potential in fluvial geormorphology of a new mineral identification technology (QEM*SEM).- Measurements of sediment toxicity of autotrophic and heterotrophic picoplankton by epifluores-cence microscopy.- A new sampler for collection of interstitial water from sandy sediments.