The estuarine system is quite rich in flora and fauna. Estuary is formed near the coastline, where the river water mixes with sea water. Estuaries are very fertile in nature.The biotic and abiotic components are as follows.
1. Biotic components - These include
(i) Producers - Producers are mainly micro flora like diatoms, green algae like spirogyra, volvox, chlorella, blue-green algae like anabaena, toria, etc., Macroflora like sea weeds, submerged grasses and rooted plants.
(ii) Consumers - The chief consumers are protozoans like noctiluca, euglena, vorticella, etc., and a large number of crustaceans, rotifers, annelids, small and large fishes, etc.
(iii) Decomposers - Bacteria and fungi disintegrate the dead organic material of the living.
2. Abiotic components - They include the organic, inorganic and climatic factors like heat, light pH, pressure, etc.
In India important estuaries are Chilka Lake in Orissa, Pulicat Lake in Andhra Pradesh and Thailanadu and Hoogly Matta in West Bengal.