Estuaries ecosystem
Estuaries are unique environments where a freshwater river or stream meets the ocean, creating a blend of both saltwater and freshwater.
These areas, characterized by their distinctive mix of water and shoreline, are known as transitional zones between rivers and seas.
Types of Estuaries
1. Salt-Wedge Estuaries
- A salt wedge estuary is a type of estuary that forms when a river's mouth flows directly into saltwater.
Examples-
- The mouths of the Mississippi, Columbia and Hudson rivers etc.
2. Open estuaries
- These estuaries are never isolated from the sea. example- Hooghly Matlah.
- The tidal impact of the system is felt upto 200 km Mahananda and Godavari is also open type.
3. Blind estuaries
- The estuaries in this category are small both in the length and catchment area during the summer the estuaries are temporary closed by the sand bar across the sea mouth during this period no tidal current.
4. Fjord
- Fjord-type estuaries are distinguished by their deep, elongated U-shaped basins and a barrier or ledge that separates the basin from the ocean.
5. Partially Mixed Estuary
- Partially mixed estuaries are characterized by a tidal flow that facilitates the removal of the salt wedge.
- This is achieved through the upward mixing of salt water and the downward mixing of fresh water.
6. Vertically Stratified or Well Mixed Estuaries
- Vertically stratified estuaries, on the other hand, have weaker tidal mixing and higher river flow, which leads to a layering effect of fresh and saltwater in the estuary.
- This layering creates distinct vertical salinity and temperature gradients, with the fresher water sitting on top of the denser saltwater.
- The boundary between the two layers is called the halocline.
- In contrast, well-mixed estuaries have a more uniform salinity and temperature profile throughout the water column, with no distinct halocline.
- The strong tidal currents in these estuaries constantly mix the water, which means that nutrients and oxygen are more evenly distributed, and the water quality is generally better.
7. Freshwater Estuaries
- Freshwater estuaries are formed when large freshwater systems, such as the Great Lakes, are mixed with water from nearby rivers or streams that drain from surrounding lands.
8. Positive and Negative estuaries-
- Positive estuaries- When fresh water inflow in estuaries exceeds evaporation.
- Negative estuaries- when the evaporation exceed the inflow high rate of evaporation increased the surface salinity.
9. Neutral estuaries-
- In this case evaporation and inflow of fresh water in equilibrium.
- These categories of estuaries are almost absent. Evaporation and inflow of fresh water are never equal.
Importance of estuaries
- Estuaries play a crucial role in supporting various animal species for nesting and breeding.
- These ecosystems are known for their high productivity and serve as habitats for a significant number of organisms that are commercially important.
- By filtering out sediments and pollutants from rivers and streams, estuaries provide cleaner water for humans and marine life.
- Estuaries also serve as essential breeding and feeding grounds for many animal species.
Characteristics of estuaries
A. Temperature
- The surface water has the greatest temperature range & the deeper water have lower temperature range.
B. Turbidity
- The water in estuaries appears turbid due to the high concentration of suspended particles in the water.
- The turbidity is minimum near the mouth and increase with distance inland.
C. Oxygen
- Due to the high level of organic matter and bacterial population in estuarine sediments, there is a substantial demand for oxygen in the water.
- Unless there is a significant number of burrowing animals present, estuarine sediments are generally anoxic below the top few centimeters.
D. Salinity
- In Estuaries, water level and salinity rise and fall with the tide Salinity of the estuaries water varies between – 0.5 and 35%.
Biota in estuary
Primary producers-
- Primary producers in estuarine systems include phytoplankton, algae, sea grasses, and salt-marsh plants.
- Larger estuarine plants are important food sources after they die and begin to decompose, although they also serve as food for some grazing aquatic animals.
- Estuarine systems usually contain multiple types of primary producers, unlike the open ocean where phytoplankton are the sole primary producers.
- Estuaries serve as nurseries of the sea as juvenile forms of many marine animals live and feed in estuaries before returning to the sea.
- Bacteria and archaea are extremely abundant on mudflats.
- They decompose the huge amounts of organic matter brought in by rivers and tides
Estuaries have high productivity because of-
- Estuaries are highly productive due to several factors, including their ability to trap nutrients both physically and biologically.
- The tidal effect in estuaries results in the accumulation of organic and inorganic nutrients, further contributing to their productivity.
- Estuaries offer a rich food source, which leads to high primary production.
- Phytoplankton in estuaries are able to efficiently use light energy, which also contributes to their high productivity.
Threats to estuaries
- Climate change.
- Poor water quality.
- Habitat loss.
- Coastal development.
- Water pollution due to industries and agriculture.
One Liner Question and answers on Estuary ecosystem.
What is an estuary?
An estuary is an environment where a freshwater river or stream meets the ocean, creating a blend of both saltwater and freshwater.
What are the types of estuaries?
The types of estuaries are salt-wedge estuaries, open estuaries, blind estuaries, fjord estuaries, partially mixed estuaries, vertically stratified or well-mixed estuaries, freshwater estuaries, and positive, negative, and neutral estuaries.
What is a salt-wedge estuary?
A salt-wedge estuary is a type of estuary that forms when a river's mouth flows directly into saltwater.
What is an open estuary?
An open estuary is an estuary that is never isolated from the sea.
What is a blind estuary?
A blind estuary is a small estuary that is temporary closed by a sandbar across the sea mouth during the summer.
What is a fjord estuary?
A fjord estuary is a type of estuary distinguished by its deep, elongated U-shaped basins and a barrier or ledge that separates the basin from the ocean.
What is a partially mixed estuary?
A partially mixed estuary is an estuary characterized by a tidal flow that facilitates the removal of the salt wedge.
What is a freshwater estuary?
A freshwater estuary is an estuary formed when large freshwater systems, such as the Great Lakes, are mixed with water from nearby rivers or streams that drain from surrounding lands.
What are positive and negative estuaries?
Positive estuaries are estuaries where the inflow of freshwater exceeds evaporation, while negative estuaries are estuaries where evaporation exceeds inflow.
What are neutral estuaries?
Neutral estuaries are estuaries where the evaporation and inflow of freshwater are in equilibrium.
What is the importance of estuaries?
Estuaries play a crucial role in supporting various animal species for nesting and breeding, provide cleaner water for humans and marine life, and serve as essential breeding and feeding grounds for many animal species.
What are the characteristics of estuaries?
The characteristics of estuaries include temperature range, turbidity, oxygen demand, and salinity.
What are the primary producers in estuaries?
The primary producers in estuaries include phytoplankton, algae, sea grasses, and salt-marsh plants.
Why are estuaries highly productive?
Estuaries are highly productive due to their ability to trap and accumulate nutrients, tidal effects, a rich food source, and the efficient use of light energy by phytoplankton.
What are the threats to estuaries?
The threats to estuaries include climate change, poor water quality, habitat loss, coastal development, and water pollution from industries and agriculture.