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Estuaries, bays and contiguous coastal seas are the world's most valuable, and yet most vulnerable marine ecosystems. Fundamental to the protection and management of these important resources is an understand- ing of the physical processes involved which affect the circulation, mixing, and transport of salt, nutrients and sediment. Residual Currents and Long-Term Transport processes appear to have direct control over freshwater inflows, contaminant loadings, dispersion and transport of sediments and nutrients, and causes of declining living resources. This volume provides a comprehensive and up-to-date summary of the research results on these processes in estuaries and bays. Contributions from ten countries include results based on theoretical formulations, analyses of field data, numerical models and case studies.

Oceanographic discontinuities (e. g. frontal systems, upwelling areas, ice edges) are often areas of enhanced biological productivity. Considerable research on the physics and biology of the physical boundaries defining these discontinues has been accomplished (see [I D. The interface between water and sediment is the largest physical boundary in the ocean, but has not received a proportionate degree of attention. The purpose of the Nato Advanced Research Workshop (ARW) was to focus on soft-sediment systems by identifying deficiencies in our knowledge of these systems and defining key issues in the management of coastal sedimentary habitats. Marine sediments play important roles in the marine ecosystem and the biosphere. They provide food and habitat for many marine organisms, some of which are commercially important. More importantly from a global perspective, marine sediments also provide'ecosystem goods and services'[2J. Organic matter from primary production in the water column and contaminants scavenged by particles accumulate in sediments where their fate is determined by sediment processes such as bioturbation and biogeochemical cycling. Nutrients are regenerated and contaminants degraded in sediments. Under some conditions, carbon accumulates in coastal and shelf sediments and may by removed from the carbon cycle for millions of years, having a potentially significant impact on global climate change. Sediments also protect coasts. The economic value of services provided by coastal areas has recently been estimated to be on the order of $12,568 9 10 y'[3J, far in excess of the global GNP.

Deposit feeders, animals that derive nutrition from organic matter in sedimentary deposits, are dominant among the inhabitants of muds and, therefore, of the benthos of much of the ocean. In this volume the critical research problems pertaining to deposit feeders are identified and promising approaches for dealing with those problems are proposed. Interdisciplinary approaches are of utmost importance in the study of deposit feeders and their sedimentary environment, merging fields as disparate as nutritional physiology and sediment geochemistry. Among the topics presented are advances in theories of foraging and digestion, and new experimental approaches to study the potential foods, feeding behavior and physiology of animals that ingest sediment.

Marine sediments provide the largest habitat on planet earth, yet knowledge of the structure and function of their flora and fauna continues to be poorly described in current textbooks. This concise, readable introduction to benthic ecology builds upon the strengths of the previous edition but has been thoroughly revised throughout to incorporate the new technologies and methods that have allowed a rapid and ongoing development of the field. It explores the relationship between community structure and function, and the selection of global examples ensures an international appeal and relevance. The economic value of marine sediments increases daily, reflected in the text with a new emphasis on pollution, climate change, conservation, and management.