Estuaries & Marshes

Estuaries

Semi-enclosed coastal embayments where fresh and salt water mix.

Estuaries are:

Highly variable, dynamically complex, among most biologically produced ecosystems

How much of economically important fish and shellfish species depend on estuaries

>2/3

How much of the US population lives within the drainage basins of coastal estuaries

>1/3

What are the estuary types by mode of formation

Coastal plain, bar-built, tectonic, fjords, deltas

coastal plain estuary

Aka drowned river valleys

Coastal plain estuary

Broad, shallow embayments formed from, V-shaped coastal river valley

Coastal plain estuary

Gradually modified by wave erosion and current patterns - reworks sediment and creates mud flats

Coastal plain estuary

Chesapeake bay, Winyah bay

Bar-built estuaries

Formed by near-shore sediments

Bar-built estuaries

Coastal obstructions can become barrier islands

Bar-built estuaries

Characterized by lower freshwater input

Bar-built estuaries

Long Island sound → glacial bar-built estuary

Tectonic estuaries

Created by subsidence of land due to crustal movements, subsequent flooding by oceanic waters and freshwater runoff into the basin

Tectonic estuaries

San Francisco Bay

Fjords

Deeply incised valleys scoured by glacial action that have opened to the sea

Fjords

Typically a shallow sill at the mouth restricts interchange between deep layers of estuary and the sea

Fjords

Deeper waters are often stagnant

Deltas

Poorly delineated estuaries with fan-shaped mouths

Deltas

Typically of high discharge, sediment-laden rivers

Deltas

Colorado and Mississippi rivers

What are land masses

Bodies of water bordered by and partially cut off from the ocean

What often flows perpendicular to the coastline

Estuaries

What has high sedimentation and erosion rates

Estuaries

What is mostly unconsidered sediments

Substrate

What are substrate examples

Mud in upper regions.

dams in channels by mouth.

natural rocky surfaces tend to be rare.

Why are mugs important in estuaries

Tend to retain higher salinity water.

provide a high salinity refuge for infauna.

What are the two estuary circulation patterns

Positive: estuary experts low salinity water to ocean, most common.

Negative: estuary experts high salinity water to ocean, Mediterranean Sea.

What can Barry due to volume of freshwater input

Positive estuary stratification types