Beginning of Essay
When examining waters transition from fresh to salt as well as from salt to fresh one quickly finds the importance of estuaries. In terms of geology, present-day estuaries are young and ephemeral coastal features. Today's estuaries began to take their current fo ....

Middle of Essay
.... lighter, or less dense, than salt water, unless the two are mixed by the tides or winds, the fresh water remains at the surface, resulting in a salinity gradient. Tides force seawater inland as a countercurrent and produce a saltwater wedge below the freshwater surface waters (Bellamy 62). Estuaries are always in a state of change and hardly ever in a steady state. The principal energy source are tides, causing estuarine mixing, but wind, wave motions, and river runoff can also be important locally (Braun 45). Salt water and fresh water mix to form brackish water. The three main estuarine ones— saltwater, brackish, and freshwater—can shift seaso ....