Sedimentary Bottoms-Beaches, Dunes

Question 1

Types of sedimentary bottom habitats

Answer 1

• Tidal flats
• Sandy beaches + dunes
• Continental shelf
• Deep sea

Question 2

What do sedimentary bottom habitats rely on the most?

Answer 2

Detritus (waste or debris) from external sources

Question 3

What do the characteristics of the seafloor depend on?

Answer 3

1. Turbulence or hydrodynamics: sorts sediment according to size
2. Benthos: colonizes and modifies sediment

Question 4

Classification of sediment by grain size

Answer 4

1. Gravel (< 2mm)
2. Sand (2mm to 63um)
3. Mud (< 63um)

Question 5

Sediment Sorting

Answer 5

1. Well-sorted (coarse): water drains quickly
2. Well sorted (fine): water drains slowly
3. Poorly sorted: water blocked

Question 6

Critical erosion velocity

Answer 6

The minimal current velocity required to erode (suspend) a sediment from the bottom

Question 7

Seafloor Stabilizers

Answer 7

Those who bind or stabilize substrate and enhance sedimentation
- Tube worms, diatoms

Question 8

Seafloor Bioturbators

Answer 8

Mine and increase vulnerability to erosion

- Rays, killifish, mud shrimp

Question 9

Trophic Amensalism

Answer 9

The interaction between deposit and suspension feeders

Question 10

What type of sediment makes up the Abyssal plains?

Answer 10

Mostly muddy sediment

Question 11

When do deep sea blooms occur?

Answer 11

Fall

Question 12

Carbon Compensation Depth

Answer 12

The depth where sinking carbonates dissolve, changing the composition of sediment below that depth
- 4000 meters

Question 13

At what depths does seafloor diversity increase and decrease?

Answer 13

Increases at 2000m but then decreases after that

Question 14

Examples of seafloor stabilizers

Answer 14

Diatoms and tube worms

Question 15

Examples of Bioturbators

Answer 15

Rays and mud shrimp

Question 16

How are beaches formed?

Answer 16

• Deposition of sandy grains over time

- Caused by weathering or the breakdown/erosion or rocks and shells

Question 17

Why are beaches red in PEI?

Answer 17

The composition of sediment determines the colour; composed of mainly sandstone

Question 18

Sediments on sandy beaches vs. dunes

Answer 18

Sandy beaches: mid to coarse sands, poorly sorted sediment

Dunes: very fine sands, very well sorted sediment

Question 19

How does water content, temperature, grain size, and compactness change along the intertidal gradient?

Answer 19

Water content: increases towards ocean
Temperature: decreases towards ocean
Grain size: increases towards ocean
Compactness: increases towards ocean

Question 20

What happens to sandy beaches in the winter?

Answer 20

• Erosion of sand
• Beach profile becomes steeper
• Dunes lose sand

Question 21

What happens to sandy beaches in the summer?

Answer 21

• Accretion of sand
• Beach profile becomes flat
• Dunes grow

Question 22

What modifies beach habitats during the seasons?

Answer 22

Wave action

Question 23

Types of sandy beaches

Answer 23

1. Reflective
2. Dissipative
3. Intermediate

Question 24

Dissipative Beaches

Answer 24

Grain size: small and fine 
Slope: gentle/flat
Waves: large and far away
Swash conditions: benign 
Diversity: high

Question 25

Reflective Beaches

Answer 25

``` Grain size: coarse Slope: steep Waves: small and nearby Swash conditions: harsh Diversity: low ```

Question 26

Rip Currents

Answer 26

Currents that run into deeper waters | - More common in dissipative beaches

Question 27

Longshore Currents

Answer 27

Currents that move parallel to the shore | - Key for spread of plankton and seaweed

Question 28

Key component in sandy beach trophic web

Answer 28

Detritus

Question 29

What do sandy beaches lack?

Answer 29

Primary producers

Question 30

Main species of macrophytes on PEI sandy beaches

Answer 30

- Rockweed - Irish Moss - Eelgrass

Question 31

Organisms found in the upper intertidal of sandy beaches

Answer 31

- Isopods and amphipods | - Ghost crabs

Question 32

Organisms found in the middle intertidal of sandy beaches

Answer 32

- Polychaetes | - Amphipods

Question 33

Organisms found in the low intertidal of sandy beaches

Answer 33

- Clams - Worms - Sand dollars - Moon snails

Question 34

How are sand dunes formed?

Answer 34

Onshore winds moving sediment (primarily saltation)

Question 35

Sediment characteristics of sand dune

Answer 35

Fine and well sorted

Question 36

What are the three types of dune systems?

Answer 36

1. Ridge 2. Parabolic 3. Transgressive

Question 37

Ridge Dunes

Answer 37

Light onshore winds and heavy vegetation binding sand

Question 38

Parabolic Dunes

Answer 38

- Medium onshore winds | - Sparse vegetation (leads to ridge failure)

Question 39

Transgressive Dunes

Answer 39

- Heavy onshore winds - Little vegetation - High mobility (unstable)

Question 40

Birds and sandy beaches

Answer 40

Beaches are used as season stopovers by migratory birds