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- What makes Apalachicola Bay an estuary?
- Geologically, what type of estuary is this?
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Apalachicola Estuary
The Apalachicola Estuary is a lagoon and barrier island complex. It has been classified as a shallow Coastal Plain estuary, but it could be called a coastal lagoon. It covers an area of approximately 210 square miles behind a chain of barrier islands, yet averages only 6 to 9 feet in depth. Its primary source of fresh water is the Apalachicola River.
You can find several definitions for an estuary:
1. An estuary is a semi-enclosed body of water which has a free connection to the open sea and within which seawater is measurably diluted by fresh water derived from land drainage.
2. An estuary is a coastal wetland where freshwater that flows from rivers and streams mixes with the saltwater from the ocean.
3. Or simply, an estuary is "where a river meets the sea".
Geologically, there are five major types of estuaries:
Coastal Plain – Millions of years ago, as ancient glaciers melted, some coastal streams and rivers became covered with water as sea levels rose. The Chesapeake Bay in Maryland and Narragansett Bay in Rhode Island are examples of coastal plain estuaries that were once river valleys.
Bar-built – Sandbars or barrier islands built up by ocean currents and waves in coastal areas created a protected area fed by small streams or rivers. The barrier islands off the Atlantic coastline of North Carolina and Massachusetts enclose bar-built estuaries.
Delta system – Deltas are formed at the mouths of large rivers from sediment and silt depositing instead of being washed away by currents and waves. When the river flow is restricted by the delta, an estuary may form. The estuaries at the mouth of the Nile River in Egypt and the Mississippi River in Louisiana are examples of delta systems.
Tectonic – Tectonic estuaries were created when a major crack or a large land sink in the Earth, often caused by earthquakes, produced a basin below sea level that fills with water. These types of estuaries usually occur along fault lines. San Francisco Bay in California is an example of an estuary created by tectonics.
Fjords – Advancing glaciers ground out long, narrow valleys with steep sides. Then when glaciers melted, seawater flooded in. Glacier Bay in Alaska is an example of a fjord.
Geologic origin of the Apalachicola Estuary
The large cusp of the entire Apalachicola coast is believed to have been built out by the Apalachicola River during the late Tertiary and Quaternary periods (2-3 million years ago) and has subsequently been modified by waves and longshore drift. The present structure of the bay system is considered to be less than 10,000 years old and the general outline of the bay has been stable over the last 5,000 years, except for the southward migration of the delta into the estuary. The present barrier island chain formation is thought to have occurred approximately 5,000 years ago when sea levels reached their current level.
The Apalachicola River is the largest in Florida and ranks 21st in the United States in terms of volume of flow. It is also one of the last remaining undammed large rivers in the country. The Apalachicola River is the only river in Florida that has its origins in the Piedmont and Southern Appalachians.
Apalachicola Bay is one of the most productive estuarine systems in the Northern hemisphere as a result of the overall good water quality. Ninety percent of Florida's oysters are harvested in Apalachicola Bay. In 1860, the City of Apalachicola did more business than all the rest of Florida combined, due to this estuarine system. UPDATE August 1, 2020: The oyster fishery is closed for five years because of a complete collapse.
https://www.apalachtimes.com/news/20200722/fwc-approves-five-year-bay-closure
To the southwest of GZ is the Apalachicola National Estuarine Research Reserve. I HIGHLY recommend a visit to this excellent facility. It is currently open Tues.-Sat. from 9-4:30. Admission is free, and they have great exhibits on the estuary, including aquarium tanks to observe the sea life found here.
Sources: dep.state.fl.us; eoearth.org; fnai.org
