Estuaries & Salt Marshes 1

Estuaries and Salt Marshes

Essential Nursery Habitat

Estuaries & Salt Marshes 2

Estuaries Dynamic habitat

where two aquatic systems meet

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Types of Estuaries Estuary classification can

be based on basin topography or salinity gradients.

Topography Drowned river valleys or

coastal plain

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Bar-built Estuary Sand bars Barrier islands NC

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Tectonic Estuaries Subsidence San Francisco Bay

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Fjords

Retreating glaciers

Sill

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Salt Wedge Positive Estuary (high tide)

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Salt Wedge Positive Estuary (low tide)

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Negative Estuary Inverse estuary High salinities

> 50‰ 100‰ or more

during dry spells

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Abiotic Factors of the Estuary Varying Salinity Substrate Varying Temperature Currents Turbidity Low Oxygen Levels

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Abiotic Factors

Salinity Tides Topography Wind Evaporation Precipitation

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Physical Factors Substrate

Rivers carry large amounts of sediment

How is sediment particle size determined by current velocity?

How is sediment oxygen concentration governed by sediment size?

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Living in the Mud

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Temperature & Currents Temperature

Varies more due to smaller volume of water and fresh water input

Water temperature also varies vertically Wave action and currents

Waves are minimal due to protection Currents are caused by the tides and river flow

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Turbidity & Light Penetration

Turbidity The amount of solid particles suspended

in the water column Increase turbidity can decrease the

amount of light which effectively penetrates

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Oxygen Where fresh and salt

water mix there is ample oxygen in the water column Oxygen solubility does

vary with the temperature (seasonal) of the water

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Salinity Tolerances

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Flora Composition Macroflora is limited due

to unsuitable substrate and increased turbidity

The dominant vegetation is emergent plants Occur in the upper

intertidal

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Types of Estuarine Communities

Open water

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Mud flats

Most animals are infauna and are usually feeding on detritus Deposit feeders

also oxygenate the sediment with their burrows

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Salt Marshes Found bordering

temperate, subpolar estuaries and marine embayments

These are communities of emergent grasses, or low shrubs rooted in soils that are alternately inundated and drained by tidal action Halophytes

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Salt Marsh Flora & Fauna Dominant plants

Spartina, Juncus, Salicornia

Dominant animals Crabs (Uca),

mussels, oysters, smaller crustaceans, amphipods, juvenile fish

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Salt Marsh Productivity Most productivity is carried out by the marsh

plants and microalgae Productivity is very high due to the emergent

plants (Spartina) Very few herbivores, most of this productivity

is not directly consumed

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Mangrove Forests

Mangals Tropical

equivalents of salt marshes

Emergent Intertidal

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