of various chemical species (carbon, oxygen, nitrogen, phosphorus, toxicants) through the environment remains: the evidence is everywhere, from fertilization of urban lakes to acid rain. The magnitude of the problem ensures that funds will continue to be made available - although with short-term variations as perceptions swing. It is thus clear that although the difficulties are great, so is the need. It is from this background that we present this book. The Port Hacking Estuary Project involved some 15 - 20 research scientists over a period of 5 years. The goal was to research the flow of carbon into, within, and out of a small unpolluted estuary chosen for convenience rather than for its social significance. The idea was to use the information obtained from these studies to build a predictive dynamic model.