Estuarine saltmarshes and mudflats

Question 1

What are mudflats?

Answer 1

The deposition of fine silts and clays in sheltered, low-energy coastal environments. They are exposed at low tide and submerged at high tide.

Question 2

What is a saltmarsh?

Answer 2

An area of coastal grassland that is regularly flooded by seawater. They are sediment sinks where river sediment is deposited close to river banks.

Question 3

What is stage 1 of saltmarsh formation?

Answer 3

Mudflat - 1. Sediment is deposited close to the high-tide line due to flocculation (suspended clay particles clump together when river freshwater meets salt water and an electrostatic effect occurs to attract the particles together)
2. Deposition occurs as sediment is too heavy to be carried
3. Pioneer plants (tolerant to high tides and inundation by salty water) form on the mudflat.

Question 4

What is stage 2 of saltmarsh formation?

Answer 4

Low marsh - 1. The mud level rises above high tide due to stabilisation by the pioneer plant roots.
2. A wider range of plants develop as conditions are drier with a lower salt content.

Question 5

What is stage 3 of saltmarsh formation?

Answer 5

High marsh - 1. Soil conditions improve further and vegetation succession forms a meadow.

Question 6

What is stage 4 of saltmarsh formation?

Answer 6

Trees and shrubs - 1. The area becomes colonised with shrubs and trees as it reaches climatic climax.

Question 7

What is flocculation?

Answer 7

When suspended clay particles clump together when river freshwater meets salt water and an electrostatic effect occurs to attract the clay particles together. As a consequence, the clay is heavier so it deposits.

Question 8

What are the threats to mudflats and saltmarshes?

Answer 8

1. Climate change - rising sea levels
2. Strong wind velocity
3. Human intervention
4. Invasive species