Aquatic Aquatic EcosystemsEcosystems

MarineMarine◦OceansOceans◦Coral ReefsCoral Reefs◦EstuariesEstuaries

EstuariEstuarieses

Enclosed body of water formed where freshwater from rivers and streams flows into the ocean, mixing with the salty sea water

River Exe estuary

A more thorough definition of an estuary would be “a semi-enclosed body of water connected to the sea as far as the tidal limit or the salt intrusion limit and receiving freshwater runoff; however the freshwater inflow may not be perennial, the connection to the sea may be closed for part of the year and tidal influence may be negligible.”

estuaries and the lands surrounding them are places of transition from land to sea, and from fresh to salt water

although influenced by the tides, estuaries are protected from the full force of ocean waves, winds, and storms by the reefs, barrier islands, or fingers of land, mud, or sand that define an estuary's seaward boundary

Estuaries are a dynamic ecosystem with a connection with the open sea through which the seawater enters accordingly to the rhythm of the tides.

The seawater entering the estuary is diluted by the freshwater flowing from rivers and streams.

The pattern of dilution varies in different estuaries and is dependent on the volume of freshwater, tidal amplitude range, and the extent of evaporation from the water within the estuary.

Estuaries are semi-enclosed bodies of Estuaries are semi-enclosed bodies of water where fresh water from the land water where fresh water from the land mixes with sea water.mixes with sea water.Estuaries originate as: drowned river

valleys, fjords, bar-built estuaries, and tectonic estuaries.

Salinity typically grades from normal marine salinity at the tidal inlet to fresh water at the mouth of the river.

a fjord is a long, narrow inlet with steep sides or cliffs, created in a valley carved byglacial activity.

A ria is a coastal inlet formed by the partial submergence of an unglaciated river valley. It is a drowned river valley that remains open to the sea. These estuaries are semi-isolated from ocean waters by barrier beaches (barrier islands and barrier spits). Formation of barrier beaches partially encloses the estuary with only narrow inlets allowing contact with the ocean waters.

Estuaries can be subdivided into three types Estuaries can be subdivided into three types based upon the relative importance of river based upon the relative importance of river inflow and tidal mixing.inflow and tidal mixing.

Salt-wedge estuaries are dominated by the outflow from rivers.

Partially-mixed estuaries are dominated by neither river inflow nor tidal mixing.

In well-mixed estuaries tidal turbulence destroys the halocline and water stratification.

Because river discharge and tidal flow vary, conditions within an estuary can also change, being well-mixed when river flow decreases relative to tidal mixing, to becoming a salt-wedge estuary at times of maximum river discharge.

The widely fluctuating environmental The widely fluctuating environmental conditions in estuaries make life stressful conditions in estuaries make life stressful for organisms.for organisms.

Estuaries are extremely fertile because nutrients are brought in by rivers and recycled from the bottom because of the turbulence.

Stressful conditions and abundant nutrients result in low species diversity, but great abundance of the species present.

Despite abundance of nutrients, phytoplankton blooms are irregular and the base of the food chain is detritus washed in from adjacent salt marshes.

The benthonic fauna strongly reflects the nature of the substrate and most fishes are juvenile forms living within the estuary until they mature and migrate to the ocean.

Estuary Estuary

EstuariesEstuaries

Estuaries are sometimes called “marine nurseries” ◦habitats for many juvenile organisms, especially for fishes

◦many fish are born and grow up in estuaries

◦migrate to the open ocean

Lagoons are isolated to semi-enclosed, Lagoons are isolated to semi-enclosed, shallow, coastal bodies of water that receive shallow, coastal bodies of water that receive little if any fresh water inflow.little if any fresh water inflow.

Lagoons can occur at any latitude and their salinities vary from brackish to hypersaline depending upon climate and local hydrology.

Bottom sediments are usually sand or mud eroded which was from the shoreline or swept in through the tidal inlet.

In the tropics, the water column is typically isothermal.

In the subtropics, salinity generally increases away from the inlet and the lagoon may display inverse flow.

Salt marshes are intertidal flats Salt marshes are intertidal flats covered by grassy vegetation.covered by grassy vegetation.Marshes are most commonly found in

protected areas with a moderate tidal range, such as the landward side of barrier islands.

Marshes flood daily at high tide and then drain through a series of channels with the ebb tide.

They are one of the most productive environments.

Marshes can be divided into two parts: Low salt marshes and High salt marshes.

Distribution and density of organisms in salt marshes strongly reflects availability of food, need for protection, and frequency of flooding.

A salt marsh is an environment in the upper coastal intertidal zone between land and salt water or brackish water, it is dominated by dense stands of halophytic (salt-tolerant) plants such as herbs, grasses, or low shrubs. These plants are terrestrial in origin and are essential to the stability of the salt marsh in trapping and binding sediments. Salt marshes play a large role in the aquatic food web and the exporting of nutrients to coastal waters. They also provide support to terrestrial animals such as migrating birds as well as providing coastal protection.A herbaceous plant (in botanical use simply herb) is a plant that has leaves and stems that die down at the end of the growing season to the soil level. They have no persistent woody stem above ground. Herbaceous plants may be  annuals,  biennials or perennials.

Salt Salt marshmarsh

Salt Salt marshmarsh

South Carolina marshes are home to many species of birds like the red-winged black bird, herons, and egrets.

These areas often serve as nursing grounds where young marine life is protected during development.

SwampSwamps s

swamps are usually regarded as including a large amount of woody vegetation

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