Sedimentary Bottoms-Beaches, Dunes Flashcards
Types of sedimentary bottom habitats
- Tidal flats
- Sandy beaches + dunes
- Continental shelf
- Deep sea
What do sedimentary bottom habitats rely on the most?
Detritus (waste or debris) from external sources
What do the characteristics of the seafloor depend on?
- Turbulence or hydrodynamics: sorts sediment according to size
- Benthos: colonizes and modifies sediment
Classification of sediment by grain size
- Gravel (< 2mm)
- Sand (2mm to 63um)
- Mud (< 63um)
Sediment Sorting
- Well-sorted (coarse): water drains quickly
- Well sorted (fine): water drains slowly
- Poorly sorted: water blocked
Critical erosion velocity
The minimal current velocity required to erode (suspend) a sediment from the bottom
Seafloor Stabilizers
Those who bind or stabilize substrate and enhance sedimentation
- Tube worms, diatoms
Seafloor Bioturbators
Mine and increase vulnerability to erosion
- Rays, killifish, mud shrimp
Trophic Amensalism
The interaction between deposit and suspension feeders
What type of sediment makes up the Abyssal plains?
Mostly muddy sediment
When do deep sea blooms occur?
Fall
Carbon Compensation Depth
The depth where sinking carbonates dissolve, changing the composition of sediment below that depth
- 4000 meters
At what depths does seafloor diversity increase and decrease?
Increases at 2000m but then decreases after that
Examples of seafloor stabilizers
Diatoms and tube worms
Examples of Bioturbators
Rays and mud shrimp
How are beaches formed?
- Deposition of sandy grains over time
- Caused by weathering or the breakdown/erosion or rocks and shells
Why are beaches red in PEI?
The composition of sediment determines the colour; composed of mainly sandstone
Sediments on sandy beaches vs. dunes
Sandy beaches: mid to coarse sands, poorly sorted sediment
Dunes: very fine sands, very well sorted sediment
How does water content, temperature, grain size, and compactness change along the intertidal gradient?
Water content: increases towards ocean
Temperature: decreases towards ocean
Grain size: increases towards ocean
Compactness: increases towards ocean
What happens to sandy beaches in the winter?
- Erosion of sand
- Beach profile becomes steeper
- Dunes lose sand
What happens to sandy beaches in the summer?
- Accretion of sand
- Beach profile becomes flat
- Dunes grow
What modifies beach habitats during the seasons?
Wave action
Types of sandy beaches
- Reflective
- Dissipative
- Intermediate
Dissipative Beaches
Grain size: small and fine Slope: gentle/flat Waves: large and far away Swash conditions: benign Diversity: high
Reflective Beaches
Grain size: coarse Slope: steep Waves: small and nearby Swash conditions: harsh Diversity: low
Rip Currents
Currents that run into deeper waters
- More common in dissipative beaches
Longshore Currents
Currents that move parallel to the shore
- Key for spread of plankton and seaweed
Key component in sandy beach trophic web
Detritus
What do sandy beaches lack?
Primary producers
Main species of macrophytes on PEI sandy beaches
- Rockweed
- Irish Moss
- Eelgrass
Organisms found in the upper intertidal of sandy beaches
- Isopods and amphipods
- Ghost crabs
Organisms found in the middle intertidal of sandy beaches
- Polychaetes
- Amphipods
Organisms found in the low intertidal of sandy beaches
- Clams
- Worms
- Sand dollars
- Moon snails
How are sand dunes formed?
Onshore winds moving sediment (primarily saltation)
Sediment characteristics of sand dune
Fine and well sorted
What are the three types of dune systems?
- Ridge
- Parabolic
- Transgressive
Ridge Dunes
Light onshore winds and heavy vegetation binding sand
Parabolic Dunes
- Medium onshore winds
- Sparse vegetation (leads to ridge failure)
Transgressive Dunes
- Heavy onshore winds
- Little vegetation
- High mobility (unstable)
Birds and sandy beaches
Beaches are used as season stopovers by migratory birds
