Estuary is the type of waters that have high variation in terms of physical factors, chemistry, biology, ecology and habitat types that form in it. Therefore, the interaction between the physical components, chemistry and biology that make up a very complex ecosystem. This is because the dynamics of the estuary is very large, both in the short time scale because of the tides and in a long time scale due to climatic changes.
Chemical Nature of Estuarine Ecosystem
Estuarine waters are defined as having a closed semi-free relationship with the sea, where freshwater from rivers and saltwater from the sea meet. So estuary is part of the river system, usually broad river, influenced by tidal action and the dynamics and physical properties such as ocean currents, waves, salinity and others. In estuarine tidal influence is dominant compared with the flow generated by wind or waves. Therefore, the behavior is very dependent on the estuarine tidal action and river flow, which both are independent variables. In general the estuary can be divided into two types, namely:
1. Positive estuary is an estuary where fresh water entering from sangai and more rain than evaporation, so that the surface salinity is lower than the open sea. Most of the estuary that there is a positive estuary.
2. Estuarine negative, ie the evaporation is greater than the flow of rivers and rain, because it will happen a state of "excessive salt" or hypersaline.