Sandy Intertidal Ecology

Question 1

what three factors are sandy beaches defined by?

Answer 1

wave action, particle size, slope

Question 2

how do the amount of organisms and particle size correlate?

Answer 2

coarse beach = few organisms.

fine beach = many organism

Question 3

why is particle size important to sandy shores?

Answer 3

• vary among the beaches, seasonally
• water retention
• desiccation
• suitability for burrowing

Question 4

how is the slope of a beach defined? what factors?

Answer 4

formed from the interaction of wave action and particle size, swash and backwash

Question 5

define swash and backwash

Answer 5

swash: water running up a beach after a wave breaks. carries particles, may accrete.
backwash: water flowing down the beach. removes particles from the beach, rate size dependent

Question 6

what are the physical factors in the sandy beach and tidal flats?

Answer 6

• wave action
• substrate movement
• heavy wave action
• light wave action

Question 7

why is substrate movement an important physical factor of the sandy shore?

Answer 7

• product of wave action
• not stable
• unlike rocky shores
• particles are (picked up, churned, re-deposited, continually moved and sorted)

Question 8

what is they physical difference between heavy wave action and light wave action

Answer 8

HWA: fine grain remains in suspension, is carried. heavy grains settle immediately, substrate of deeper depth affected.
LWA: only particles close to surface are affected, substrate stabelizers.

Question 9

what is the affect of substrate movement, and how is it a habitat changer?

Answer 9

affects limitation of biotic diversity.

changes habitat through stabelization, submerges aquatic vegetation and benthic animals.

Question 10

describe a dissipative beach

Answer 10

wave action is strong, wave energy is dissipated over a broad flat surf zone, located away from the beach face. Results in gentle swash and fin sediments.

Question 11

Describe a reflective beach

Answer 11

FRANCE
wave action impinges directly on beach face, sediment is coarse, no offshore surf zone, waves produce large swashes, beach slope is steep, backwash and swash collide to deposit sediment, wave energy is directed against the face of the shore.

Question 12

what conditions are the best to support more abundant fauna? (regarding type of beach)

Answer 12

highly exposed beach better than less exposed, dissipative, not reflective.

Question 13

what type of fauna is associated with dissipative beaches?

Answer 13

high biomass of filter feeders

Question 14

what is the difference between winter and summer profiles?

Answer 14

-wave action changes:

gentle wave action replaced by heavier ( grain size, profile, uniformity, physical factors, sand depth).

Question 15

what are the differences between sandy shores profile and rocky shores?

Answer 15

-smooth, uniform profile, lack topographical diversity, no crevices, overhangs, permanent tide pools, slopes facing different directions.

Question 16

how does the uniform profile of sandy beaches reflect in environmental factors?

Answer 16

Environmental factors are uniform:

• temp, desiccation, wave action and salinity
• insulating properties in sand
• interstitial water
• density of salt water
• buffers

Question 17

why is the O2 content never limited in beach water?

Answer 17

• turbulence of wave action
• ensures saturation
• limit in temperature change
• needs replenishement

Question 18

what is the organismal diversity is sandy shores, and what is it lacking?

Answer 18

Has: seagrasses, ephemeral algae, polychaetes, bivalve molluscs, crustaceans
-lacks: large plants, sessile organisms

Question 19

what are the main organisms you would find at the sandy shore?

Answer 19

• annelids (polychaetes)
• Molusca (razor clams)
• arthropods

ALSO: a diatom layer on the surface of the sand.

Question 20

what is the feeding biology of the inhabitants of the sandy intertidal?

Answer 20

-phytoplankton carried in
-organic debris
-other beach animals
THEREFORE:
-filter feeders, detritus feeders, scavengers. A few resident carnivores and opportunists.

Question 21

Who are the main suspension feeders? what do they feed on?

Answer 21

bivalve molluscs, razor clams, surf clams, coquiinas. they feed on plankton, resuspended organisms.

Question 22

who are the filter feeders, how do they feed, what do they feed on

Answer 22

• sand crabs trap debris in wash
• Olivella create a mucus net
• sand dollars
• bivalves and polychaetes

Question 23

deposit feeders: what do they feed on, who are they in the PNW.

Answer 23

• detritus feeders
• convert detrital organic material into macrofaunal biomass
• significant bioturbators
• Maldanid polychaete

Question 24

what are the sandy shores zones? who occupies these zones?

Answer 24

• Supralittoral fringe: fast movers, excavate burrows, scavengers (sand fleas)
• midlittoral zone: barnacles, isopods, sand crabs
• infralittoral zone: surf zone, greatest number of species, large surf clams, sand dollars, polychaetes, crustaceans.

Question 25

do an overview of slide 30/35

Answer 25

‘generalized sheme of zonation on sandy shores’

Question 26

–> over view slide 33/35, sand flat structuring via competition. a little unsure

Answer 26

3D vs rocky shores:

there is more protection when there are rocks present, although there are starfish and molluscs? idk.

Question 27

Grant 1981

Answer 27

amphipod burial depth. competition vs preference