Organisms and ecological interactions of the sandy shores and mudflats

Question 1

Microfauna

Answer 1

<63 micrometres

Often interstitial: living in or between sediment grains

Question 2

Meiofauna

Answer 2

63-500 micrometres
Can be interstitial
Often larval forms

Question 3

Macrofauna

Answer 3

> 500 micrometres
Larger than interstitial space
true burrowing organisms

Question 4

Burrowing organism’s adaptations to oxygen limitations (4)

Answer 4

Connections to the surface of the sediment or with water using siphons, tubes and creating water movement

Some move or leave when oxygen becomes too low

Reduction of feeding activity and movement

Efficient oxygen-binding pigments in the blood

Question 5

Detritus breakdown stages (3)

Answer 5

Fragmentation (physical break-down)
Leaching (loss of dissolved material such as pigments)
Microbial colonization and decay (by fungi and bacteria)

Question 6

Microbial stripping hypothesis

Answer 6

Predicts that infauna are not just eating detritus, but also the microbes that are that cause detritus to decay and rot
Microbial decay of detritus improves nutritional value (increases nitrogen content) and easier to digest

Question 7

Bioturbation

Answer 7

A local-scale biological disturbance which changes the environment in a way that influences other organisms
How the animals influence sediments, and it has a cascading biological effect

Question 8

Bioturbation effects (5)

Answer 8

Increase habitat structure and complexity

Reworks sediment (changes in size distribution)

Changes sediment chemistry (oxygen incursion, bio-irrigation)

Increase microbial activity (oxygen changes, microbial gardening)

Changes habitat (provides new habitats available for other organisms, prevents others from colonizing)

Question 9

Space competition in the mudflats

Answer 9

Because they are working in a 3D environment the density is much lower
Space competition isn’t really isn’t a problem
Different depths mitigate competition

Question 10

Soft shore predation

Answer 10

Soft shore predation is likely evenly distributed
Partial predation is more common
Sea birds provide seasonal predation

Question 11

Soft shore supply side

Answer 11

Larval supply is important as meiofauna have different patterns

Similar strategies for larval settlement, but the settlement does not affect adult distribution as adults are mobile

Question 12

Soft shore zonation

Answer 12

Not as stark or well understood

Upper zone that contains air breathers

There is a lower zone that is mostly wet and contains many marine organisms

In between those zones is likely a mix of organisms with not much zonation

However, the shape of the beach affects how it becomes zoned