Estuaries

Question 1

What is an estuary

Answer 1

An estuary is a semi enclose body if water where the sea meets fresh water

Question 2

What is the salinity if sea water and fresh water

Answer 2

Sea water salinity 35
Fresh water salinity 0

Question 3

What are the 4 types of estuaries

Answer 3

Tectonic formed by tectonic activated along a fault line
Fjord formed by glacial activity
Coastal plain essentially a flooded river valley
Barrier which are partially separated from the sea by a barrier e.g. sand bar

Question 4

Tectonic estuaries

Answer 4

Sinking of land through tectonic activity allowed flooding of the area by the sea which is diluted by freshwater from the river catchment

Question 5

Fjord estuaries

Answer 5

Very deep steep sides valleys for,ed by glacial retreat
Fauna that lives in these are similar to fauna in the Atlantic
Fjord water doesn’t mix much with seawater due to morainal sill
Mixing only occurs due to wind however caring penetrate to depths and mostly confined to the surface

Question 6

Costal plain estuaries

Answer 6

Flooded coastal plain gives rise to large areas of shallow estuaries frequently exposed at low tide mainly formed by sea level rise. They are extremely productive (mud flat salt marsh environments)

Question 7

Barrier estuaries

Answer 7

Relatively small and are separated from the sea by sand bars. Lagoons are associated with barrier estuaries

Question 8

Salinity in estuaries - salt wedge

Answer 8

Salt water is more dense than freshwater. High river flow keeps salt water at bay therefore salt water forms a wedge as it moves up the estuary by being pushed by tides. This creates a saltwater wedge beneath the freshwater

Question 9

What is partially mixed salinity

Answer 9

Salinity varies with depth with a moderate seaward flow

Question 10

What is well mixed salinity

Answer 10

Incoming sea water mixed with freshwater with little variety in salinity with vertical depth

Question 11

Salinity in fjord

Answer 11

Deep waters in fjords tend to have an even salinity. Freshwater move seaward near the surface. Mixing occurs only about the depth of the sill (20m) deeper waters tend to be saltier due to density

Question 12

Dynamics of estuaries

Answer 12

Estuaries although low energy environments are dynamic

The course of the river channels often change
There is considerable sediment erosion , transportation and deposition

Question 13

How do diatoms stabilise estuary sediment

Answer 13

Diatoms are single cell organisms that move through the sediment with tides to avoid predation. The move via a chemical EPS. EPS sticks the sediment together due to the huge number of diatoms

Question 14

How do mussels stabilise estuary sediment

Answer 14

By creating mussel bed