Estuaries

1. Estuaries Sunita Heeraman 7th Period

2. Description of Location • partially enclosed body of water along the coast where fresh water from rivers and streams meets and mixes with salt water from the ocean • they are places of transition from land to sea and freshwater to salt water.

3. Food Chain

4. Type of Water and Habitat • The water in estuaries is a mix of salt and fresh water which serves as a transition between the land and oceans. • They are under the influences of both oceanic and riverine processes, such as tides, currents, and the flow of sediment. • An estuary is partly enclosed, with several rivers and streams flowing it, and then connecting to the ocean. • Habitats associated with estuaries include salt marshes, mangrove forests, mud flats, tidal streams, rocky intertidal shores, reefs, and barrier beaches. • They also provide homes for fish, crabs, and shorebirds who rely on estuarine processes.

5. Humans and Estuaries • 22 of the 32 largest cities in the world are located on estuaries. • The Chesapeake and San Francisco Bays are home to large, economically and militarily important harbors. • Large numbers of commercially valuable fish return from the ocean to spawn in the closed-off waters of saltmarshes and mangroves. • Oysters, clams and other shellfish thrive in bays and inlets, as do many species of crabs and fish.

6. Threats Fishing is a frequent activity in estuaries, and can deplete the population: Chesapeake Bay once had a flourishing oyster population which has been almost wiped out by overfishing. Historically the oysters filtered the estuary's entire water volume of excess nutrients every three or four days. Today that process takes almost a year. • Estuaries are under threat from human activities such as pollution and overfishing. They are also threatened by sewage, coastal settlement, land clearance and much more. Estuaries are affected by events far upstream, and concentrate materials such as pollutants and sediments. Land run-off and industrial, agricultural, and domestic waste enter rivers and are discharged into estuaries. Contaminants can be introduced which do not disintegrate, such as plastics, pesticides, furans, dioxins, phenols and heavy metals.