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AQUATIC HABITATS



AQUATIC HABITATS

WHAT IS AQUATIC HABITAT?

Aquatic habitat is a body of water in which certain organisms live naturally. In other words, aquatic habitats are habitats or places that relates to lives in water.


Organisms that live in water are called aquatic organisms. Examples of aquatic organisms are fish, crabs, toads and plants.

Types of aquatic habitats

There are three types of aquatic habitats. These are:
1. Marine or salt water habitats.
2. Estuarine or brackish water habitats.
3. Fresh water habitats.





MARINE HABITATS

Marine habitats refer to aquatic habitats which contain salt water. Marine habitats include the oceans, lakes, shores and the open seas.

CHARACTERISTICS OF MARINE HABITAT

The marine or salt water habitat has the following characteristics:
1.

Salinity:

salinity is the degree of saltiness or concentration of salt solution in oceans. The marine habitats have a high salinity and its average salinity is put at 35.2 per 1000. In other words, the average salinity of the ocean is 35.2 parts of salts by weight per 1000 parts of water.
2.

Density:

the density of a marine water is high, hence many organisms can float in it. While the density of ocean water is about 1.028, that of fresh water is 1.00. So, the density of ocean water is higher than that of fresh water.

Pressure:

water pressure increases in depth at the rate of one atmosphere for every ten metres. In other words, pressure varies from one atmosphere at the surface level to about 1000 atmosphere at the greatest depth. This is why animals in marine habitats have features which enable them to adapt especially at the deep level of the sea.



3.
4.

Size:

marine habitats represents the largest of all the habitats. The ocean alone occupies over 70% or 360 million square kilometres of the earth’s total area of 510 million square kilometres. Examples of oceans are Atlantic Ocean, Pacific Ocean, (the largest), Indian Ocean etc.
5.

Currents:

currents are always produced by wind at the surface of the ocean. Currents are also produced down the ocean as a result of certain variations such as salinity and changes in temperature.
6. Tides: tides are the alternate rise and fall of the surface of the ocean approximately twice a day. This alternate rise and fall in water level is due to the gravitational effects of the moon and sun.
7.

Oxygen concentration:

the concentration of oxygen in the ocean is the highest at the surface while it decreases with depth, and in every deep parts of the ocean there is practically no oxygen.
8.

Hydrogen ion concentration:

salt water is known to be alkaline in nature with pH of about 8.0-9.0 near the surface.
9.

Waves:

waves are movement of surface waters of the oceans and it can take any direction and are caused by winds. Waves bring about the mixing of sea water especially on the surface of the ocean.
10. Light penetration: light penetrates the ocean water only to a maximum depth of 200 metres. Therefore, plant life is limited to the upper layers of the ocean where light can penetrate. Penetration of light depends on the water turbidity.

MAJOR ZONES OF THE MARINE HABITATS

Supratidal or splash zone:this is the exposed zone of the marine habitat. It has occasional moisture since it is the area where water splashes when the wave break at the shore.
2.

Intertidal or neritic zone:

this zone which is also called planktonic or euphotic zone is only exposed at low tide or covered by water at high tide. It has high photosynthetic activities because of abundant sunlight. There is also fluctuation of the water temperature.
3.

Littoral or sub tidal zone:

this zone is about 200m deep. It is constantly under water, it has abundant sunlight and therefore abundant nutrients.
4.

Benthic zone:

benthic zone is also under water and is about 500m deep. It has low light penetration and low nutrients.
5.

Pelagic or abyssal zone:

this zone is about 7000m deep. It has low temperature, low light penetration, high pressure, low photosynthetic activities and the primary production of food is by chemosynthesis.
6.

?Hadal or aphotic zone:

this is the deepest zone of the marine habitat. It is over 7000m deep. It forms the floor or bed of the ocean. There is no light penetration and no photosynthetic activities.
7.

On the basis of depth or light penetration or vertical zoning of marine habitat, there exist three major zones.

These are euphotic, disphotic and aphotic zones.

i.

Euphotic zone:

this is an area which is directly connected with sunshine. Producers, consumers and decomposers are present here. There is enough light penetration for photosynthesis to take place.
ii.

Disphotic zone:

this is a region of dim light. Consumers and decomposers are also found there. Light penetrates water but the intensity is too low for photosynthesis to take place.
iii.

Aphotic zone:

this represents the bottom or bed of the seas and oceans. It is characterized by cold dark water without light penetration and very few living organisms are found in this zone.





DISTRIBUTION OF ORGANISMS IN MARINE HABITATS AND THEIR ADAPTIVE FEATURES

The organisms in marine habitats include plants and animals.

PLANTS IN MARINE HABITAT

1. Sea weeds: they possess hold-fast for attachment. They also possess mucilaginous cover to prevent dissociation. They have divided leaves, floating devices or air bladder for buoyancy.
2. Algae, e.g. sargassum: algae possess chlorophyll for photosynthetic activities, small size or large surface area for drifting or floating.
3. Sesuvium: Sesuvium possesses thick leaves or reduced leaves for water conservation.
4. Planktons, e.g. diatoms: they possess air spaces in their tissues, rhizoids (fake feet) for attachment to rocks and air bladder for buoyancy.

ANIMALS IN MARINE HABITAT AND THEIR ADAPTIVE FEATURES

1. Barnacles: barnacles have protective mantle or pad for attachment or anchorage to rock shore, cilia for feeding, shell which prevents desiccation and mantle which retains water.
2. Cartilaginous fishes: cartilaginous fishes like shark and dog fish have ability to retain urea in their body to cope with high salinity.
3. Bony fish: fishes like tilapia and herring drink salt water to cope with high salt content of the ocean. They also possess salt secreting gland in their gills or eyes to enable them maintain osmoregulation or salt balance.
4. Shrimps: they possess powerful claws or chelipods for seizing or holding food or prey.
5. Crabs: crabs are capable of burrowing fast into the mud to protect them against predators, strong waves or tides.
6. Periwinkles: they possess lungs for breathing and foot for attachment.
7. Starfish: they possess tube feet which enable them to hold on to rock shores, and hard shell which prevents desiccation or drying up.

FOOD CHAIN IN MARINE HABITAT

A typical food chain in marine habitat could be up to three or four trophic levels. The phytoplanktons, e.g. diatoms serve as the major producers which support the food chain. Some examples of food chain includes:
i. Diatoms==Zooplanktons==Tilapia==Shark
ii. Diatoms==Crabs==Tilapia

FACTORS AFFECTING MARINE HABITATS

Some of the major factors affecting marine habitats are temperature, sunlight, wind, density, pH and salinity. These factors have been explained under characteristics of marine habitats.

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