The mixing of salt water and fresh water results in the formation of brackish water
. This brackish water is what is called estuarine.
It is the transition zone between rivers and the open sea, characterized by changing salinity levels, tidal fluctuations, and diverse environmental conditions.
Estuaries can be found along coastlines worldwide and come in various forms, including bays, lagoons, inlets, and deltas.
Estuarine habitats are incredibly productive and support a wide array of plant and animal species.
They serve as important nurseries and feeding grounds for many marine organisms, including fish, crustaceans, molluscs, and birds.
The mixing of fresh and saltwater in estuaries creates a unique blend of habitats, such as mudflats, salt marshes, seagrass beds, and mangrove forests, which provide valuable resources and shelter for various species.
Types of Estuarine habitat
Estuary is found in the following bodies of water
a delta is where a river divides into many channels before entry into the ocean or sea. Brackish water or estuary (delta) is formed at the mouth of a river as it enters the sea.
Lagoon of Estuarine Habitats:
the lagoon is a body of ocean water that enters into the land through a canal and therefore has the opportunity of mixing with fresh water from rivers and streams.
Bay of Estuarine Habitat
bay is a little or small portion of the seawater which enters into the land and mixes up with fresh water from rivers and streams.
It should be noted that a lagoon is bigger than a bay and it may be long enough to join the sea at another end while a bay is very small and not long enough to rejoin the sea at another end.
Characteristics of Estuarine Habitat
The followings are the characteristics of the estuarine habitats:
fluctuation in salinity of Estuarine Habitats:
salinity fluctuates in this habitat. Salinity is also affected by season. While the rainy season reduces salinity due to the addition of fresh water, the dry season increases it.
turbidity of Estuarine Habitats:
turbidity of estuarine habitat increases especially during the rainy season when lots of debris are brought down by rivers to the habitat. This high turbidity also reduces the rate of photosynthesis and respiration by organisms.
the shallowness of water in Estuarine Habitats:
unlike the sea water which is deep, the water in estuarine habitats is very shallow.
low species diversity of Estuarine Habitat:
the estuarine habitat has low diversity of species compared to marine habitat.
water is affected by tides of Estuarine Habitats:
seawater usually flows rapidly into estuaries at high tides and rushes back into the ocean at low tides.
high level of nutrient of Estuarine Habitat:
the low oxygen content of Estuarine Habitats:
oxygen content of estuarine habitat is generally very low and as a result, much of the microbiological activities are anaerobic.
DISTRIBUTION OF PLANT AND ANIMALS IN ESTUARINE HABITAT
Plant Species and Their Adaptive Features
planktons (diatoms) of Estuarine Habitats:
they possess air spaces in their tissues, rhizoids or false feet for attachment to rocky shores and air bladder for buoyancy.
algae of Estuarine Habitats:
red mangrove (Rhizophora racemosa) of Estuarine Habitat:
it has silt roots which grow down from the stem into the soft mud and develop numerous rootlets which have air spaces for conducting air to the tissues of the roots.
The roots also provide support and prevent plants from being washed away by the tides. Again the seed of red mangrove germinate while they are still on the parent plant thereby preventing the seedlings from being carried away by water current.
white mangrove (Avicenna nitida) :
it has pneumatophores or breathing roots for exchange of gases.
Animal Species and Their Adaptive Features
mosquito larvae and pupae of Estuarine Habitats:
these organisms possess breathing trumpets for gaseous exchange.
crabs of Estuarine Habitats:
they can burrow fast into the mud against predators, strong waves or tides.
water snails and shrimps of Estuarine Habitats:
these animals can burrow into the mud when the tide is going out, thus escaping the periodic dilution of its external medium.
worms of Estuarine Habitats:
they have strong protective and impermeable covering against high salinity.
mud skippers of Estuarine Habitats:
these animals have fins adapted for crawling when on land and for swimming when in water.
fishes of Estuarine Habitats:
fishes like tilapia have fins for movement and swim bladders for buoyancy. read more on classification of fishes
Food Chain in Estuarine Habitat
A typical food chain in an estuarine habitat may have up to three, four or five trophic levels. The phytoplanktons such as diatom and detritus form the basic producers which support the food chain.
Some examples of food chains in the estuarine habitat are:
Factors Affecting Estuarine Habitat
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