Aquatic ecology and Biodiversity

Practical 14- Study of estuarine habitat and organisms

Experiment No. 14
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Estuaries are partially enclosed bodies of water along coastlines where fresh water and salt water meet and mix. Estuary is acting as a transition zone between oceans and continents. It has a free connection with the ocean. Fresh water input from land sources dilutes the estuary's salt content. They characerstic feature or the estuary is the mixing of fresh and salt water Pritchard (1967) defined as"An estuary is a semi-enclosed coastal body of water which has a free connection with the open sea and within which sea water is measurably diluted with fresh water derived from land drainage."

Estuaries are vital habitats for many marine and fresh water species. They are called the "nurseries of the sea" Salinity Variations in salinity are affected by temperature, dissolved gases, density and viscosity. Salinity in the estuary varies with depth, flux of fresh water, and changes with the tide.Temperature: Shallow estuarine waters exhibit great temperature changes. Oxygen: Some estuaries have very low oxygen levels. Sediment: Particle size and chemistry of estuarine sediments can make a difference in the organisms that can survive. Infiltration of the estuarine sediments by nutrients, trace elements, sewage and industrial waste can influence the productivity of the estuary.Wave action: reduced wave action in turn promotes the deposition of sediments and development of rooted plants in the estuarine regions.Turbidity: As this region is having good amounts of fine sediments or particles, turbidity of the estuarine waters is very high in most of the periods. The highest turbidities are known to occur during the maximum freshwater discharge into the estuaries.
Morphology of estuary:

• Depth
• Width
• Speed of water
• Point of joining to the sea

Characteristics of water
Physical: Temperature----------- Colour / Odour---------------- Turbidity---------
Chemical: pH------------------ Do---------------- Salinity----------------------------
Estuarine communities – Plankton, Benthos, Fishes etc.
Species diversity and association
Inferences