Estuaries

Question 1

What is the definition of an estuary? And what are the characteristics?

Answer 1

• Estuaries are semi-enclosed bodies of water that have a permanent or intermittent connection with the ocean and within which sea water is measurably diluted with fresh water deriving from land drainage.
• Dynamic ecosystems, in a constant state of flux.
  ○ Because they get constant input from the seawater and a river
• Zones of mixing and deposition
• Ecology is different from either adjacent freshwater or coastal ecosystems

Question 2

What are the 4 most common estuary types? And which one is the most common one)

Answer 2

1. Drowned river valley (most common)
2. Fjords
3. Tectonically formed estuary
4. Bar-built estuary

Question 3

What are the characteristics of drowned river valleys?

Answer 3

Most common type of estuary, relatively flat and shallow. They have delta. Delta is where the river is depositing all the particles that flow down the river, and when the flow gets to zero the particles stop and form a delta.

Question 4

What are the characteristics of fjords?

Answer 4

Drowned glacial valleys, deep often with a sill at the mouth

Question 5

What are the characteristics of tectonically formed estuaries? And name an example of tectonically formed estuary.

Answer 5

They are formed by the same process tectonic lakes are formed, only difference is that faults happen close to the ocean and by the land.
Example: San Francisco Bay

Question 6

What are the characteristics of bar-built estuary?

Answer 6

Drowned river valleys with high sedimentation rates that create a bar. Sedimentation from river create sand bars instead of creating a delta.

Question 7

What is a tidal prism?

Answer 7

Volume of water that flows into and out of an estuary during one tidal cycle.

Question 8

There can be 4 types of salinity gradients in estuaries, draw them.

Question 9

What is a salt water wedge?

Answer 9

Salt water that climbs up to a river because of less flow in the river.

Question 10

What are the main characteristics of sedimentation in estuaries?

Answer 10

○ Estuaries are low flow areas, so smaller particles precipitate
○ Few air pockets in mud, low O 2 penetration
○ Few meiofauna, more microfauna
○ Oxic and anoxic sediment layers

Question 11

What are the 3 types of organisms in an estueary?

Answer 11

Estuarine organisms consist of:
○ Those of marine origin
§ Salinity above 25
○ Those of freshwater origin
§ Salinity below 10
○ True estuarian species
§ Most common in salinities 5-18

Question 12

What are the four main adaptation factors in organisms that live in estuaries?

Answer 12

• Salinity – Organisms must be able to tolerate (or avoid) large changes in salinity
• Migration – Many migratory organisms use estuary habitats for part of their life cycle
• Sedimentation – Organisms must cope with high sedimentation rates and fine particle, soft-bottom substrates
• Flow and Tidal Flux – Organisms must tolerate (or avoid) various directional flows

Question 13

What is osmoregulation?

Answer 13

Osmoregulation is the process by which an organism maintains the balance of water and dissolved materials in its body fluids in relation to its environment. It’s a vital process for metabolic activities like thermoregulation, electrolyte balance, and the excretion of toxic waste.
* In freshwater a fish has to hold on to ion and try excrete water as much as possible
* In saltwater a fish has to hold on to water and excrete ion

Question 14

What are the tree diadromy life history types?

Answer 14

Anadromy
Catadromy
Amphidromy

Question 15

In terms of river continuum, how is the estuary?

Answer 15

• Primary productivity and detritus both contribute to high secondary productivity
• Organisms adapted to utilize pre-processed particulate organic material (POM)
• Species diversity is relatively low
• There are no shredders because there are no FPOM