Aquatic Ecosystems

Life inside our water

Fresh water naturally occurs in ponds, lakes, rivers, streams, etc. Salt water is water from an ocean or sea. Brackish water is the 'in between', for it contains more salt than fresh but less than sea water. The definitions themselves show the differences, but they do have similarities. Of course, they all have the same chemical structure that make up H2O. All the waters are home to aquatic life and contain minerals. They're also used for transportation. (Mainly salt and fresh though)


Salt water

Salt water, also known as seawater, is denser than both fresh and brackish water. It contains more ions than all types of fresh water. The salinity of ocean water is about 3.5 percent.

Fresh water

Fresh water is divided into systems. Stillwaters (pond, lake, swamp, etc) and running water (groundwater that flows in rocks and aquifers). It is a renewable element but restricted natural resource. Fresh water organisms can breath only underwater. You won't find mammals (such as Dolphins) in fresh water.

brackish water

Also known as briny water, it occurs from the mixing of fresh and salt water. Often times brackish water will occur with estuaries, which is when a river meets the sea. For example, the Thames River in London is known as freshwater, but between Battersea and Gravesend the river is brackish. Some estuaries are: Chesapeake Bay, Amazon River, and lower Hudson River. Some general brackish waters are: Baltic Sea, Black Sea, Caspian Sea, Lake Charles, Lake Monroe, and Lagos Lagoon.