Final - Esturaries

Question 1

What are the two estuary classifications based on?

Answer 1

1. Geology
2. Stratification and Fresh-Seawater Circulation

Question 2

What are the 5 geology classifications?

Answer 2

1. Coastal-plain estuaries or drowned river valleys
2. Fjord-type estuaries
3. Tectonically caused estuaries
4. Delta estuaries
5. Bar-built estuaries -> Lagoons

Question 3

Describe drowned river valleys

Answer 3

Formed by glaciers carving the valleys, sea level rise which then flooded the gently sloping bottoms.
Sediment then accumulated within the river valley.

Question 4

Describe fjord-type estuaries

Answer 4

Fjords are valleys that have been cut deeper by moving glaciers and then invaded by the sea.

Created by glacial action, characterized by the steep slope of adjacent lands and great depth

Shallow sill near their mouth that limits water exchange between the deeper waters of the fjord and the sea

Question 5

Describe tectonic estuaries

Answer 5

movement in the earth’s crust causes a large piece of land to sink (subside) producing a depression that is infilled by seawater

created when the sea fills in the “hole” or basin that was formed by the sinking land.
ex. San Francisco Bay

Question 6

Describe delta estuaries

Answer 6

form at the mouths of large rivers, when sediments and silt accumulate rather than being washed away by currents or ocean waves

over time, a complex set of channels and marshes form at the mouth of the river

sediments continue to accumulate seaward

Question 7

Describe Bar-Built Estuaries

Answer 7

rarest type of estuary on the West Coast

formed by ocean waves and currents pushing sediments shoreward, building up sandbars and forming barrier islands (potentially leading to the estuary becoming permanently blocked)

Stream typically has low flow most of the year (high salinity)

Question 8

What are the five major types of classifications for estuaries by stratification and circulation?

Answer 8

1. Salt-wedge
2. Fjord
3. Slightly stratified
4. Vertically mixed
5. Freshwater

These classifications are a result of the degree to which fresh and saltwater mix is measured using isohalines (think contour lines on a topo map)

Question 9

What is the Isohaline and what does it indicate?

Answer 9

ISOHALINE: area in the water of equal salinity

The shape of the isohaline indicates the amount of MIXING (may give clues about the underlying geology)

Question 10

Define Salt wedge estuaries

Answer 10

Most stratified (least mixed) estuary type aka Highly Stratified

Occur when a rapidly flowing river discharges into the ocean where tidal currents are weak. Some mixing occurs at boundary, but generally slight.

The location of wedge varies with tidal conditions and discharge
ex. Fraser River

Question 11

Describe Fjord type estuaries (in terms of circulation)

Answer 11

found along de-glaciated coastlines

Sill at entrance restricts water circulation and dense seawater seldom flows up over the sill into the estuary
very little tidal mixing; thus, the water remains highly stratified.

Not all Fjord estuaries by stratification are Fjord estuaries by Geology. ex Puget Sound is a Fjord by Geo but Slightly Stratified by Circ.

Question 12

Describe Slightly Stratified Estuaries

Answer 12

also known as ‘partially mixed’ estuaries
saltwater and freshwater mix at all depths

the salt water is mixed upward and fresh water is mixed downward
lower layers of water typically remain saltier than upper layers

very deep estuaries, such as Puget Sound (WA) and San Francisco Bay (CA)

Question 13

Describe vertically mixed estuaries

Answer 13

“well-mixed” estuary, occurs when river flow is low and tidal currents are moderate to strong

Strong tidal currents eliminate layering of freshwater above seawater

salinity is the same from water surface to the bottom of the estuary due to strong tidal currents

found in large, shallow estuaries

Question 14

Define Freshwater estuaries

Answer 14

Exclusive to the Great Lakes

Not seawater, but chemically-distinct combinations of river and lake water

Not tide-driven but STORM-DRIVEN (“seiches”)
semi-enclosed bay areas in which the lake water becomes mixed with water from the river or stream

Question 15

What is Thyroxine and what is it believed to regulate in smolts?

Answer 15

Thyroxine is a hormone that salmon smolts have in elevated concentrations during juvenile estuary residency.

Thyroxine is thought to regulate neurogenesis, and influence neural development in the salmon olfactory system, and facilitate olfactory imprinting

Question 16

Salmonids, being anadromous, require a critical period of estuary residency to:

Answer 16

As smolts, physiologically adapt from fresh to salt water

Consume prey and grow large enough to migrate to the ocean

Avoid being eaten by predators

As adults, physiologically adapt from salt water to reproduce in freshwater

Question 17

What are the 4 salt ions in water and where do they come from?

Answer 17

dominated by Cl- and Na+, followed by SO4-2 and Mg+2

‘salts’ originate from continental weathering, submarine vents and leaching out of the ocean floor

Question 18

What temperature is the maximum density of freshwater?
What about for saltwater?

Answer 18

4°C
Density decreases above or below 4°C.

in saltwater, density increases progressively to freezing point of -2°C. salts add mass without adding volume

Question 19

True or False: Saltwater increases density with decreasing temp?

Answer 19

True

Higher density promotes sinking of cold sea water, which drives global ocean circulation

Question 20

What is the pycnocline?

Answer 20

a layer in an ocean or other body of water in which water density increases rapidly with depth.

The pycnocline is the depth gradient in salinity

Question 21

What does mixing of the water in estuaries rely on?

Answer 21

1. the direction and speed of the wind
2. the tidal range (the difference between the average low tide and the average high tide)
3. the estuary’s shape
4. the volume and flow rate of river water entering the estuary

Question 22

What was a key take-away from the 1986 Fraser Estuary study?

Answer 22

In the Fraser estuary study, chinook and chum showed an increase in average length which was attributed to estuarine growth, compared to pink.

Pink salmon had the shortest residency period in the estuary. Chum residency was intermediate at 11 days. Chinook spend the most time there - up to 30 days.

Question 23

What abiotic factors determine the distribution of marsh species (vegetation)?

Answer 23

Inundation (linked to elevation)
Degree of tidal fluctuation
Salinity
Nutrient availability

Operate in the Fraser on a west-east gradient (less salinity going east) as well as along an elevational gradient (slopes upwards)

Question 24

In estuaries, where are the more specialized species located and why?

Answer 24

Located lower in elevation in areas of greater salinity stress. Less specialized species are found at higher elevations with less salinity.

Question 25

What are some biotic factors that determine the distribution of marsh species (vegetation)?

Answer 25

Herbivory
Invasive species
Competition

Question 26

How can one restore urban estuaries?

Answer 26

By restoring the natural gradients and structures that create and maintain habitat conditions - ecosystems will then respond.

Your restoration template is reference estuaries with intact physical gradients and structure, connected estuary habitats.

Question 27

What is a surface flow fluvial gradient?

Answer 27

Fluvial energy relative to ocean energy influences estuary form, habitats, salinity, biota, etc.

It influences the depositional features (sandbars, mudflats, etc).

Question 28

What is a subsurface fluvial gradient?

Answer 28

Subsurface “Hyporheic Zone”

Subsurface exchange of fresh and saltwater ions, nutrients. Contains microbial activity and redox reactions

Question 29

What is a platform view tidal gradient?

Answer 29

The tidal height (flux), influences the horizontal extent of the tidal zone (combined with the river mouth morphology)

Influences the extent of estuary habitats available for organisms over the range of tidal flux

Tidal height and salinity stress gradient.

Question 30

What is the lateral tidal gradient impacted by?

Answer 30

It’s impacted by river training devices (dykes, jetties).
(Consider how “edge habitat” and “connectivity” change with tide)

Question 31

Describe the salinity gradient. What determines the gradient?

Answer 31

Salinity is affected by river discharge, tidal flux, winds, shoreline revetment, substrate, delta bathymetry, evaporation, and more

Determines what plant species can establish and where

Influences the distribution of organisms

Question 32

Name the salinity gradients in order from Marine to the limit of tidal influence, and salinity in ppt.

Answer 32

Marine: Euhaline >30ppt

Salt marsh & mangroves: Mesohaline 5 - 30ppt

Brackish marsh & forest: Oligohaline 0.5 - 5ppt

Tidal freshwater marsh & forest: <0.5ppt

Non-tidal freshwater marsh & forest: Limit of tidal influence

Question 33

What is the light penetration gradient and what is it influenced by?

Answer 33

Photic Zone = Photosynthetic Zone
Influenced by turbidity, sediment load of the river, water depth
Affected by structures, log booms, piles
Influences phytoplankton, extent of submerged plant community

Question 34

What are the stressors related to the use of Piles and Dikes?

Answer 34

1.Interferes with sediment deposition and erosion processes

2.Reduces flow circulation through shallow-water habitats, side-channels, and peripheral bays

3.Reduces connection to refuge habitats

4.Release of toxic contaminants into the water and sediments where pile structures are treated with preservatives (creosote)

5.Pilings favor predators of salmonids, such as northern pike minnow, smallmouth bass, double-crested cormorants

Question 35

What are the 4 main estuary gradients?

Answer 35

Tidal
Fluvial
Salinity
Light penetration

Question 36

Estuary wood dynamics - What degrades the wood and recycles its nutrients and energy?

Answer 36

1. Isopods - wood boring isopod crustacea (gribbles)
2. Wood-boring mollusks (shipworms)
3. Fungi
4. Bacteria

Question 37

What were the two key changes to the Modernized Migratory Bird Regulations, 202?

Answer 37

Hunting and Harvesting - recognized aboriginal and treaty rights to hunt migratory birds and harvest eggs without a permit, bag limit/open season/possession limit.

Charity Permit - may serve migratory game birds at a charity function or food kitchen, or provide them to a food bank.

Question 38

What affects eelgrass characteristics?

Answer 38

Density and morphology vary by depth, wave exposure, substrate, water clarity

Question 39

How deep eelgrass grows depends on chemical and physical factors. Name all 8.

Answer 39

*Amount of light available
Water clarity
Water temperature
*Salinity (10-30 ppt)
pH
*Elevation
*Substrate
Wave action

*Are the most important

Question 40

What is an ESS?

Answer 40

Ecologically Significant Species

No legal protection, but intended to bring attention to its high ecological significance and promote a greater degree of risk averse management regarding any human activities that may impact eelgrass or its community properties

Question 41

What are the main anthropogenic impacts on eelgrass in estuaries?

Answer 41

Dredging
Excess nutrient loading and chemical contamination.
Logging
Land development
Oil spills
Docks
Anchoring
Boat propeller cuts
Invasives - European Green Crab

Question 42

What is the eelgrass transplant procedure?

Answer 42

1. Assess the reference and donor site for the proposed eelgrass transplant (good site characteristics?)
2. Select donor plants with similar morphological characteristics that will survive in the new location.
3. Obtain necessary permits
4. Assemble team and equipment
5. Attach a ~12 mm dia. non-galvanized steel washer to each plant near the base with a twist tie, and place in seawater tubs, in preparation for the divers to plant
6. Plant eel grass in selected grids
7. Monitor the effectiveness of your transplant. Adaptive management if necessary!

Question 43

What stratification class are geologically classified ‘fjord’ estuaries, and what factors control their stratification process?

Answer 43

Fjord - often Slight Stratified or Fjord circulation

Sill is the main control of circulation

Question 44

What stratification class are the estuaries of some major west coast rivers (Fraser), which have a rapidly flowing river discharge into the ocean where tidal currents are relatively weak?

Answer 44

Salt Wedge

Question 45

Rank Chinook, Pink, and Chum salmon in order of time spent in an estuary before moving offshore into the marine environment. (Order of increasing time spent)

Answer 45

1 - Pink. Least time spent
2 - Chum
3 - Chinook. Most time spent

Question 46

What are the two dominant life-history strategies of Chinook salmon? Which occupies the FRE for a longer duration as juveniles?

Answer 46

Stream/River type
Ocean type - this type spends longer in the estuary

Question 47

What is the general salinity range for brackish (estuary) water, expressed in ppt?

Answer 47

O.5 - 30 ppt

Question 48

Why does saltwater sink relative to freshwater?

Answer 48

Because it is more dense than freshwater

Question 49

Carbon is the currency of estuaries. What are the 4 inputs of carbon?

Answer 49

Marsh vegetation
Estuary vegetation
River transported carbon
Ocean transported carbon