Sandy and Muddy Shores Flashcards
What kind of fauna are found in soft shores?
Mobile epifauna and infauna.
Define porosity.
The volume of pore space in between particles. Small particles fill up spaces and reduce porosity.
Define permeability.
Rate of percolation of water through sediment. Reduced by low porosity.
What is water content of soft beaches determined by?
Particle size, beach profile and water table height.
What are dilatant sands?
When pressured, they become dry and hard packed as water is driven out of the interstices. Difficult to burrow into.
What are thixotropic sands?
Quicksands. High clay content means they become wetter and more easily penetrated when agitated. Easier to burrow into.
What are muds?
They do not drain and are saturated with water. They are soft and easy to burrow into.
What kind of fauna are found in rocky shores?
Sessile and mobile epifauna.
What is the redox potential discontinuity?
The depth below the sediment-water interface marking the transition from chemically oxidative to reducing processes.
What kind of plant life is found on soft shores?
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.
What sort of meiofauna (>45um - 0.5/1mm) are found on soft shores?
Nematodes, ostracods, polychaetes (temporary), ciliates,
What sort of macrofauna (>0.5/1mm) are found on soft shores?
Lugworms (Arenicola), shore crabs, urchins, anemones, ragworm (nereis), snails, cockles, clams.
How is species richness affected by particle size?
Richness, abundance and total biomass increase with increasing sediment stability & therefore decreased particle size (decreased wave exposure).
Is there clear zonation in soft shores?
Lack of distinct vertical zonation - sediments buffer physical stressed & organisms are mobile. Deeper burrowing in intertidals. ZOnation related to hydrodynamics.
What determines distribution on a soft shore? (3pt)
Particle size, emersion period, depth of water table.
How did soft shore organisms live in the Cambrian and Ordovician?
Primarily on the surface or 0.5-10cm below the sediment.
How did soft shore organisms live in the Devonian?
Fauna created extensive and deep burrows extending to the outer shelf.
What did infauna become large scale?
In the mesozoic.
When did lugworms originate?
The triassic - 30cm burrow depth, intensively bioturbating - 44cm^3 per day!
What are biostabilisers?
Flora/fauna that:
+Increase cohesiveness
+Make sediment smoother
+Form protective layer over sediment surface.
What are bioturbators? (6pt)
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)
How do microalgae stabilise sediment? (5pt)
+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.
