MSCI 575 - Quiz 3; Estuaries and Shores

Estuary

an inlet of the sea reaching into a river valley

3 Sectors of an Estuary

1) lower; open to the ocean, 2)middle; strong mixing, 3)upper; freshwater

Estuaries and lagoons make up ______ of coastline along the Atlantic and Gulf Coast

80-90%

Estuaries and lagoons make up _____ on the Pacific Coast

10-20%

For most estuaries, NET water flow is ____ of the estuary at the surface and ______ the estuary along the bottom.

Out, into

Estuaries can be classified based on features such as;

Geomorphology, Circulation and Hydrography, Salinity and Tides, and Sedimentation

Classification based on Geomorphology….

• Coastal Plain, Drowned River Valley

• Coastal Plain, Bar-Built

• Tectonically-Produced

• Fjord-Type

Drowned River Valley Estuaries

Most common, formed by sea level rise, and tide and river-dominated

Bar-built estuaries

Longshore currents form a sandbar, lack a major river source, and are usually shallow, wind-dominated.

Tectonically-Produced Estuaries

Formed by earthquakes, common on active coasts, create basins that become filled with water.

Fjord-Type Estuaries

Deep, built by glaciers, shallow sill, sill may trap anoxic bottom water

Classifications of estuaries based on circulation are usually based on

the “average” condition

Classifications of estuaries based on Circulation;

Salt-wedge, Partially Mixed/Two-Layer Flow, Well-mixed, and Fjord

Salt Wedge Estuary

High salinity stratification, river discharge dominates over tidal action,

Partially Mixed/Two-Layer Flow

Moderately salinity stratified, tidal flow increases relative to river discharge,

Well Mixed Estuary

Salinity is vertically homogenous, with intense tidal flow and strong turbulent mixing, sometimes caused by strong winds.

Fjord Type Estuary (Circulation)

Formed by glaciers at high latitudes, sill results in “stagnant” bottom waters, usually highly stratified.

Estuaries classified based on sedimentation

Positive-filled, Inverse-filled, and Neutral-filled

Positive-filled (sedimentation)

Estuaries that are filled entirely by river-transported sediment.

Inverse-filled (Sedimentation)

Estuaries filled by beach and nearshore sediment

Neutral-filled (Sedimentation)

No change in basin volume due to sediment input and output.

What is mixing?

The process where a water mass is diluted or redistributed within other water masses.

What is Flushing Rate?

The rate required to replace the existing freshwater in an estuary.

What is Residence Time?

The time required to replace the freshwater in an estuary

Estuarine organisms originate from two possible sources….

1) freshwater origin extending into estuaries from rivers

2) marine species colonizing estuaries from the sea.

Isosmotic

An organism with blood concentration the same as the external concentration

Hyper-osmotic

Blood is more concentrated than external concentration.

Hypo-osmotic

Blood concentration is less than the external concentration.

Osmoregulators

Maintain certain conditions with environmental change

Osmoconformers

Changing body chemistry to match the environment.

The distribution of many infaunal organisms is determined by what?

Availability of mud habitat

A key factor in determining the local distribution of the mysid is?

Flow areas

The only physiochemical parameter that is significantly related to the distribution pattens of the brown shrimp is?

Dissolved oxygen concentration

A dominant variable influencing the movement and distribution of many estuarine fish species is?

Temperature

Intertidal Migration

movement of animals into and out of the intertidal zone on each tide.

What are the benefits of intertidal migration?

Maximize food intake, maximize reproductive output, and minimize predation keeping to deeper waters.

What are some physiological adaptations for survival in estuaries?

Osmoregulation, wide salinity tolerance, and migration.

Estuarine organisms demonstrate three responses to increases in flow and large decreases in salinity, what are they?

1) They tolerate the changes.

2) They migrate or drift to avoid low salinity

3) They don’t survive at all

What are Salt Marsh systems?

Production where the estuary meets the land.

Salt marshes are sites of high _____ productivity

Secondary

What are 5 marsh functions that make them valuable to fish and other organisms?

1) Reproduction

2) Foraging

3)Refuge from predation

4) Refuge from stressful environmental conditions

5)Environmental enhancement of physiology

As salt marsh functions vary across spatial gradients within the marsh and over tidal, diel, and seasonal time scales, how do organisms adapt to this?

They migrate within the estuary to exploit the functions available.

Anadromous

Adults live in the sea and migrate to freshwater for breeding

Catadromous

Adults live in freshwater and migrate to the sea for breeding.

Amphidromous

Species that migrate back and forth, but not for breeding purposes.

Alpha diversity

The number of species present in an individual sample

Beta Diversity

Compares the variations in diversity between different samples

Shores occur….

where land meets the sea.

Why do species occupy different sections of environmental gradients?

Because they have different physiological and ecological tolerances

What are the four main gradients that can be recognized on shores:

1. Wetness/Dryness

2. Exposure to wave action

3. Substratum particle size

4. Salinity

The wetness/dryness gradient is set up at the tension between _____ and ____.

Water and Air

Wave action is a major determinant of….

Community structure, composition, individual shape, form, and behavior.

Shallow sloping offshore areas tend to _____ energy in the waves.

dissipate

Steeper cliffs with deep water at their base experience ______ physical impact of wave action.

much greater

The size of particles that make up the shore determine what?

the kinds of organisms that can live there

______ provide a stable surface for attachment so epifauna (on top of) and flora dominate these shores.

Large particles

________ are often too unstable to permit surface attachment and fauna lives within the beach.

Finer particles

What are zonation patterns?

the overall patterns of distribution and abundance

What causes zonation patterns?

Physiological tolerance (upper), competition and predation (lower)

Why are zonation patterns harder to detect on sandy beaches and mudflats?

Space is not as much of a constraint because fauna are mobile and will relocate to avoid competition.

Shore communities are organized by a combination of what two processes?

top-down (consumer-driven) and bottom-up (resource-driven).

Primary Space

The actual structure itself.

Secondary Space

The space that is created when things land on top of primary space.

Sandy and muddy shores are particularly vulnerable to _______ because they are often prevented from transgressing inland (coastal squeeze).

climate change induced sea-level rise.

Coastal Squeeze

When marshes cannot migrate inland due to a man-made barrier restricting them.