What are the four most important estuary types?
- Salt wedge estuary
- Well mixed estuary
- Partially mixed estuary
- Reverse estuary
What is an estuary?
A semi enclosed coastal body of water
Has free connection to open sea at least intermittently
The salinity is measurably different from the salinity in the open sea
Describe a salt wedge estuary
- forms where a ledge river inputs lots of freshwater in an area that the tidal range is low
- the exiting freshwater holds back a wedge of intruding seawater
Describe a well mixed estuary
- forms where rivers input smaller amounts of freshwater
- tidal range is moderate to high
- well mixed conditions tend to occur in shallow estuaries
Describe partially mixed estuaries
- transitionally between salt wedge and we’ll mixed types
- occur in deeper estuaries
Describe reverse estuaries
- form along arid coasts where rivers cease to flow
- the evaporation of seawater in the upper most reaches cause water to flow from the ocean in to the estuary
Describe the thermohaline current process
Warm water rises to the top of the ocean waters as it is less dense
Cold water sinks as it is dense
As cold water freezes it releases salt in to the water making it even saltier and more dense
Second part of thermohaline process
Cold water travels from pole latitudes along the ocean surface towards the equator , as it heats up it rises once again due to becoming less dense.
Same process for warm water travelling to polar latitudes, freezes, releases salt more sense sinks
How does thermohaline occur?
It is temperature and salinity based.
The circulation results from surface changes of temperature and salinity.
What is used to measure light penetration?
Secchi depth
What does photosynthesis depend on?
The availability of light.
Productivity occurs only when rates of photosynthesis exceed rates of respiration.
What is photosynthetic primary production?
The foundation for food chains
