Distribution of Organisms in an Estuary

Plants: We have

  1. Red mangrove, Rhizophora sp. which is the main species of flowering plant in the lagoons or estuaries and
  2. White mangrove, Avicennia sp. occur in areas of higher salinity and drier land than the red
  3. Plankton protists such as diatoms, and flamentous algae.
  4. Fern plant, Acrostilchumaureum (the only fern able to withstand salt water) grows in this habitat, so also are
  5. Numerous grasses (paspalum sp.)

Red Mangrove

Animals: We have

  1. Invertebrates: Mitten crabs, starfish, arenicola, mudskipper, lancelet and barnacles. The animals commonly found in the estuaries or lagoons are those that can withstand salinity variations and they include the bloody clam, common lagoon crab, hermit crab, the hairy mangrove crab, the fiddler crab, cichlids, the prawns, Ethmalosa, Arins, and the grey mullet (Mugil).
  2. Birds: Such birds as the herons, waders and palm nut vulture are found here.
  3. Mammals include bats and monkeys.

File:Eriocheir sinensis (Chinese mitten crab), Lentse Waard, the ... Chinese Mitten crab

Adaptations of Estuarine Organisms

Adaptations of Plants

White mangrove has breathing roots to permit intake of atmospheric air and their leaves can excrete salts.

The red mangrove has still roots to enable it to withstand strong ocean winds

To ensure development of the seedlings and to avoid being swept off by ocean current, some seeds germinate on the parent plant.

Adaptations of Animals

Crabs have air-breathing lungs-like structures for breathing.

Starfish have tube feet to hold fast.

Barnacles and starfish have shell- like covering to protect them from drying up.

Food Chain in Estuarine Habitat

  1. Diatoms    →    Small fish    →    Shark    →    Man.
  2. Detritus     →     Shrimp    →     Fish    →     Bird.


  1. List some organisms of the brackish water.
  2. Write two each of the adaptation of plants and animals in estuarine habitat.
  3. Write a short note on the types of estuarine with examples.
  4. List five types of freshwater bodies.
  5. Briefly explain three types of estuary.

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