Aquatic Habitat – Marine

Meaning of Aquatic Habitat

An aquatic habitat is a body of water in which organisms live. Such organisms are called aquatic organisms e.g. fish, algae, crabs, etc.

Types of Aquatic Habitat

There are three types of aquatic habitat namely:

  1. the marine/salt water habitat;
  2. the estuarine/brackish water habitat and
  3. the freshwater habitat.

Marine Habitat

The marine habitat is a body of salty water. It is made up of the shore and open sea. Examples are the oceans and seas.

Characteristics of Marine Habitat

  1. High salinity; about 35.2 parts of salt per 1000 parts of water.
  2. High densityof about 1.028; this enables organisms float in it.
  3. Pressure increases with depth.
  4. It is the largest of all habitats. It occupies over 70% of Earth’s total area.
  5. There is action of waves.
  6. There is tide action alternate rise and fall in level of sea water twice a day.
  7. The water is alkalinewith pH of 8.0 – 9.0 near the surface
  8. Oxygen concentration decreases with depth.
  9. Light penetration decreases with depth.
  10. Currents are always produced by windsat the surface of the ocean.


  1. What is a marine habitat?
  2. State five characteristics of a marine habitat.

Major Zones of a Marine Habitat

It has two major zones, the

(i) Littoral zone

(ii) Benthic zone

(i) Littoral Zone (Continental shelf)

This zone is sub divided into:

(a) splash zone

(b) intertidal zone

(c) sub-tidal zone

(a) Splash zone: this zone is just above the high tide mark, and is wetted by the spray from breaking wave. It has occasional moisture since it is the area where water splashes when the waves break at the shore.

(b) Intertidal zone: This covers the shoreline between the high and low tides. The zone is covered with water during high tide and exposed to air during low tide. This happens twice daily. The zone is exposed to wave action and has high photosynthetic activities because of abundant sunlight

(c) The Sub-tidal zone: This is the zone that extends over the continental shelf to a depth of about 200metres. The zone experiences more variations in temperature, water turbulence, salinity and lightning more than any other zone. It is the main site of commercial fish harvest. Its high productivity is attributed to its richness in nutrients, a large part of it being in the lighted (photic) part of the ocean.

(ii) Benthic zone (Continental slope)

This zone is characterized by:

(a) Benthic zone: This consists of the deep water that extends beyond the continental shelf, from about 500m to the very depths of the ocean. It has very low light penetration and low nutrients.

(b) Pelagic or abyssal zone: This zone is about 3000m, and has low light penetration, high pressure, low photosynthetic activities and the primary production of food is by chemosynthesis.

(c) Hadal or aphotic zone: It is the deepest zone, ranging from 7000m. The water is dark and cold, i.e. no light penetration, and on photosynthetic activities.

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