Estuarine and soft sediment environments Flashcards
What is an estuary?
A coastal area where a river meets the sea
Vary in size, type and origin = affects their ecology
What are the four main types of estuaries?
- Drowned river valley
- Fjord
- Bar-built estuary
- Tectonic estuary
What is a halocline?
A vertical salinity gradient in the water column
Shows how salinity changes with depth
What is an isohaline?
A line of equal salinity
What are the major physical characteristics of estuaries?
- Salinity
- Substrate
- Other factors like temperature and turbidity
Affects what organisms can live there
What factors influence salinity in estuaries?
Sand or soft mud, which is often anoxic due to bacterial respiration
Anoxic mud can limit which species live there
How does biodiversity compare in estuaries?
Lower species diversity but higher biomass
Species must tolerate extreme conditions
What are euryhaline organisms?
Species that tolerate a wide range of salinities
Most esturarine organisms
What are stenohaline organisms?
Species that tolerate a narrow range of salinities
May enter estuaries but wont thrive below 30 ppt
What does “brackish” refer to?
Salinity between freshwater and seawater; optimal for many estuarine species is 3–10 ppt
Organisms wont be found in open sea
What is osmoregulation?
The process of maintaining salt and water balance in an organism’s body
Crucial for survival in changing salinity
What is the difference between osmoconformers and osmoregulators?
Osmoconformers change with salinity (e.g., salmon); osmoregulators maintain internal salt levels (e.g., polychaete worm)
Some species can switch
How do estuarine plants adapt to salinity?
They absorb salts and concentrate sugars or excrete salts (e.g., spartina has salt glands, Glasswort absorbs water to dilute salts)
What are the main primary producers in soft-bottom communities?
Seagrass
How does sediment grain size affect soft-bottom environments?
- Coarse = drains quickly
- Fine = drains slowly
- Poorly sorted = water retention
Grain size shapes habitat conditions
What are the three benthic size categories?
- Microfauna
- Meiofauna
- Macrofauna
Meiofauna live between sediment grains and indicate environmental quality
Give examples of infauna in estuarine environments
Lugworms and cockles
Burrow under sediment
Why are estuaries important for birds?
High invertebrate biomass supports many bird species, often on migratory paths
Key feeding grounds
What characterizes open-water estuarine communities?
Marine species brought in by tides, supporting rich fisheries
Name two fish that can live in estuaries full-time
Golden grey mullet and European eel
