AmasSeds: An Interdisciplinary Investigation of a Complex Coastal Environment

A MULTIDISCIPLINARY Amazon Shelf SEDiment Study (AmasSeds) is being undertaken on the continental shelf near the mouth of the Amazon River. Details of the AmasSeds international research project are described in the five papers which follow. The present paper outlines the justification, background and approach of the overall project. On the Amazon shelf, between the Parfi estuary and the Brazil-French Guiana Border (Fig. 1), material input (water, solutes, particulates) and energy expenditure (tides, currents, winds, waves) are enormous. This situation produces a myriad of complex interdependent oceanic processes. Sediment is a common link between the diverse processes, because most of them affect and/or are affected by the particles found on the Amazon shelf. The fundamental justification for AmasSeds research is that a number of unique oceanic processes are active near the mouths of very large rivers (e.g., Amazon, Huanghe, Changjiang, Ganges-Brahmaputra), and that these processes cannot be understood solely by extrapolation from observations of smaller river systems. For example, the papers which follow will demonstrate that biological productivity (pelagic and benthic) and cycling of many geochemical components (inorganic and organic) are largely controlled by the immense discharge of sediment particles. The freshwater discharge of the Amazon displaces typical estuarine circulation from the river mouth into the three-dimensional setting of the shelf, where it is superimposed on marine circulation. Extremely high supply rates of sediment to the Amazon shelf create fluid muds (concentrations > 10 g 1 -~) which severely affect marine sediment