Sandy and Muddy Shores

Question 1

What kind of fauna are found in soft shores?

Answer 1

Mobile epifauna and infauna.

Question 2

Define porosity.

Answer 2

The volume of pore space in between particles. Small particles fill up spaces and reduce porosity.

Question 3

Define permeability.

Answer 3

Rate of percolation of water through sediment. Reduced by low porosity.

Question 4

What is water content of soft beaches determined by?

Answer 4

Particle size, beach profile and water table height.

Question 5

What are dilatant sands?

Answer 5

When pressured, they become dry and hard packed as water is driven out of the interstices. Difficult to burrow into.

Question 6

What are thixotropic sands?

Answer 6

Quicksands. High clay content means they become wetter and more easily penetrated when agitated. Easier to burrow into.

Question 7

What are muds?

Answer 7

They do not drain and are saturated with water. They are soft and easy to burrow into.

Question 8

What kind of fauna are found in rocky shores?

Answer 8

Sessile and mobile epifauna.

Question 9

What is the redox potential discontinuity?

Answer 9

The depth below the sediment-water interface marking the transition from chemically oxidative to reducing processes.

Question 10

What kind of plant life is found on soft shores?

Answer 10

Generally no macroalgae, but sometimes blooms of Enteromorpha and Ulva on mudflats/Spartina on saltmarshes. Brown seaweeds e.g. Fucus present if attached to pebbles.

Question 11

What sort of meiofauna (>45um - 0.5/1mm) are found on soft shores?

Answer 11

Nematodes, ostracods, polychaetes (temporary), ciliates,

Question 12

What sort of macrofauna (>0.5/1mm) are found on soft shores?

Answer 12

Lugworms (Arenicola), shore crabs, urchins, anemones, ragworm (nereis), snails, cockles, clams.

Question 13

How is species richness affected by particle size?

Answer 13

Richness, abundance and total biomass increase with increasing sediment stability & therefore decreased particle size (decreased wave exposure).

Question 14

Is there clear zonation in soft shores?

Answer 14

Lack of distinct vertical zonation - sediments buffer physical stressed & organisms are mobile. Deeper burrowing in intertidals. ZOnation related to hydrodynamics.

Question 15

What determines distribution on a soft shore? (3pt)

Answer 15

Particle size, emersion period, depth of water table.

Question 16

How did soft shore organisms live in the Cambrian and Ordovician?

Answer 16

Primarily on the surface or 0.5-10cm below the sediment.

Question 17

How did soft shore organisms live in the Devonian?

Answer 17

Fauna created extensive and deep burrows extending to the outer shelf.

Question 18

What did infauna become large scale?

Answer 18

In the mesozoic.

Question 19

When did lugworms originate?

Answer 19

The triassic - 30cm burrow depth, intensively bioturbating - 44cm^3 per day!

Question 20

What are biostabilisers?

Answer 20

Flora/fauna that:
+Increase cohesiveness
+Make sediment smoother
+Form protective layer over sediment surface.

Question 21

What are bioturbators? (6pt)

Answer 21

Flora/Fauna that:
+Make sediment surface rougher.
+Regrade the sediment particle structure.
+Reduce sediment strength.
+Oxygenate sediment
+Modify geochemistry profiles
+Often exclude filter feeders (amensalism)

Question 22

How do microalgae stabilise sediment? (5pt)

Answer 22

+They live in the top 1-2mm of sediment, forming biofilms.
+Secrete mucous (Extracellular Polymeric Substances) to migrate
+EPS increases cohesiveness of sediment.
+Biofilm reduces bed roughness.
+Effect greatest in spring/summer + on upper shores.