Unit 2 - Estuarine Ecology

Question 1

What are estuaries?

Answer 1

semi-enclosed bodies of water where freshwater from rivers mixes with seawater

Question 2

What do estuaries originate as?

Answer 2

Drowned river valleys, Fjords, Bar-built estuaries, Tectonic estuaries

Question 3

What is the most common origin and setting of estuaries?

Answer 3

Drowning of the mouth of a river valley.

Question 4

What is the origin of estuaries in high latitudes?

Answer 4

glaciers have carved deep, narrow, steep-walled valleys, and many have glacial moraines.

Question 5

How do bar-built estuaries evolve?

Answer 5

spit extension across an embayment.

Question 6

How do tectonic estuaries commonly result?

Answer 6

block faulting

Question 7

What are the three types of estuaries based on the relative importance of river inflow and tidal mixing?

Answer 7

Salt-wedge estuaries, partially mixed estuaries, well-mixed estuaries

Question 8

What happens in salt-wedge estuaries based on river inflow and tidal mixing?

Answer 8

dominated by river outflow, stratified with halocline

Question 9

What happens in well-mixed estuaries based on river inflow and tidal mixing?

Answer 9

Tidal turbulence destroys halocline and water stratification

Question 10

What causes varying conditions within an estuary?

Answer 10

River discharge and tidal flow

Question 11

How can an estuary become well-mixed?

Answer 11

when river flow decreases relative to tidal mixing

Question 12

When can an estuary temporarily become salt wedge?

Answer 12

times of maximum river discharge, usually during spring snowmelt

Question 13

How are estuaries defined?

Answer 13

mixing characteristics between freshwater and seawater inputs

Question 14

What type of currents characterize salt-wedge estuaries?

Answer 14

a net landward-directed bottom current and a net seaward-directed surface current

Question 15

What type of currents characterize partially mixed estuaries?

Answer 15

strong currents,with net landward-flowing bottom currents andnet seaward-flowing surface currents

Question 16

What type of currents characterize well-mixed estuaries?

Answer 16

net currents that are landward-directed at all depths on one side of the estuary and seaward-directed flow at all depths on the other

Question 17

Why is species diversity low in estuaries?

Answer 17

Stressful conditions and abundant nutrients responsible; best adapted organisms dominate their ecological niche.

Question 18

What factors contribute to the low number of species in estuaries?

Answer 18

Widely fluctuating environmental conditions, abundant nutrients, and competition among organisms

Question 19

How often do phytoplankton blooms occur in estuaries?

Answer 19

Despite abundance of nutrients, phytoplankton blooms are irregular.

Question 20

What commonly forms the base of the food chain in estuaries?

Answer 20

Detritus washed in from adjacent salt marshes

Question 21

What do benthic fauna in estuaries reflect?

Answer 21

the nature of the substrate.

Question 22

How do juvenile fish utilize estuaries?

Answer 22

Juvenile fish live in estuaries before maturing and migrating to the ocean.

Question 23

How do estuaries assist in trade?

Answer 23

efficient, overseas transportation of goods, agriculture and oil

Question 24

What food do we get from Estuaries?

Answer 24

crabs, clams, fish

Question 25

What habitats do we get from estuaries?

Answer 25

fish "nursery" areas, waterfowl

Question 26

How are Estuaries Threatened?

Answer 26

Pollutants, Nutrients and eutrophication, Shoreline development, Habitat loss, Mariculture, Overharvesting, Invasive species transported in ballast water

Question 27

What are lagoons?

Answer 27

Shallow bodies of coastal water that receive little to no freshwater inflow.

Question 28

How do lagoons vary in salinity?

Answer 28

from brackish (mixed with freshwater) to hypersaline (extremely salty), depending on climate and local hydrology.

Question 29

Where can lagoons occur?

Answer 29

at any latitude and range from completely isolated to semi-enclosed.

Question 30

What are the typical bottom sediments in lagoons?

Answer 30

Sand or mud eroded from shoreline or swept in through tidal inlet

Question 31

What is the characteristic of the water column in lagoons in the tropics?

Answer 31

typically isothermal

Question 32

How does salinity generally change in lagoons in the subtropics away from the inlet?

Answer 32

increases; may induce inverse flow

Question 33

Where are salt marshes commonly found?

Answer 33

areas protected from high-energy waves, winds, or currents like the landward side of barrier islands.

Question 34

What happens to salt marshes daily at high tide?

Answer 34

They flood, then drain through channels w/ ebb tide.

Question 35

Why are salt marshes considered productive environments?

Answer 35

They are one of the most productive environments on Earth.

Question 36

What type of environment do salt marshes grow in?

Answer 36

Muds and sands sheltered by barrier islands

Question 37

How are salt marshes classified based on topography and plant assemblages?

Answer 37

As low or high marshes

Question 38

What are the two parts of salt marshes?

Answer 38

Low salt marsh and high salt marsh

Question 39

How are salt marshes often characterized in terms of vegetation?

Answer 39

By dominant grasses with different degrees of salt tolerance

Question 40

What factors strongly influence the distribution and density of organisms in salt marshes?

Answer 40

Availability of food, need for protection, frequency of flooding

Question 41

How do mussels contribute to the ecosystem in marshes?

Answer 41

fertilize sediments and helps stabilize them

Question 42

What role do fiddler crabs play in marsh ecosystems?

Answer 42

Burrowing oxygenates sediments, consumption of organic matter helps cycle nutrients back into the marsh

Question 43

How do plants benefit animals in marsh ecosystems?

Answer 43

protection from predation and buffer from potential physical stresses

Question 44

What is a prominent feature of a salt marsh?

Answer 44

Pannes

Question 45

What are pannes?

Answer 45

Small, isolated pools of water occurring in areas of low elevation

Question 46

How are pannes formed?

Answer 46

when surface layers of organic debris are decomposed by bacteria.....high tides and runoff water fill pannes

Question 47

How do large vascular plants modify salt marsh habitats?

Answer 47

They stabilize and trap sediment, buffer waves and currents, and oxygenate the sediments.

Question 48

What role do large vascular plants play in salt marsh habitats?

Answer 48

make habitat more habitable to other plants and animals

Question 49

What does salt marsh evolution record?

Answer 49

interaction between river input and coastal ocean, including SLR.

Question 50

What dominates the youthful stage of salt marsh evolution?

Answer 50

Low marsh.

Question 51

When is the stage of mature development reached in salt marsh evolution?

Answer 51

When about one-half of the salt marsh consists of high marsh.

Question 52

What causes more vertical growth of the marsh surface in salt marsh evolution?

Answer 52

Additional deposition of sediment.

Question 53

What is the final stage of salt marsh evolution where the entire wetland is high marsh?

Answer 53

Old marsh.

Question 54

What does the position and character of a salt marsh reflect?

Answer 54

Retreat or advance of the ocean/river interface

Question 55

How does longshore drift of sand protect a cove?

Answer 55

From direct wave attack

Question 56

What happened by 400 B.C. in relation to the salt marsh evolution?

Answer 56

The spit had elongated considerably, and high marsh had extended into the bay covering older low-marsh deposits

Question 57

What has continued to happen in the salt marsh evolution up to the present?

Answer 57

Spit growth, mud deposition, vertical growth of wetlands resulting in dominantly high-marsh communities

Question 58

What is the stage known as 'old marsh' in the salt marsh evolution?

Answer 58

Dominantly high-marsh communities resulting from mud deposition and vertical growth of wetlands

Question 59

What does a sediment core show?

Answer 59

The stages of marsh development

Question 60

HUMAN IMPACTS

Answer 60

Rotary Ditching, Marsh Impoundment, Eutrophication, Restoration, Introduced Species