Aquatic zones-Fresh Water-Marine-Estuaries

Aquatic zones-Fresh Water-Marine-Estuaries

Aquatic zones-Fresh Water-Marine-Estuaries

  • These are not called biomes.
  • The major differences between the various aquatic zones are due to –
  • o Salinity
    o Levels of dissolved nutrients
    o Water temperature
    o Depth of sunlight penetration.

Fresh Water Ecosystems

These can be classified as Lentic (still water (pond)) and lotic (moving water)


 Lentic: slow-moving water, including pools, ponds, and lakes.

 Lake ecosystem –

Lake ecosystems can be divided into 3 zoneslittoral, Photic and Aphotic zone.

  • Littoral zone – It is the shallow zone near the shore. This is where rooted wetland plants occur.

    The offshore is divided into two further zones, an open water zone, and a deep-water zone.
  • Open water zone (or photic zone) – In this zone sunlight supports photosynthetic algae and
    the species that feed upon them.
  • Deepwater zone – In this zone sunlight is not available and the food web is based on detritus entering from the littoral and photic zones.
Aquatic zones-Fresh Water-Marine-Estuaries


  • Lotic: faster-moving water, for example- streams and rivers.
  • The major zones in river ecosystems are determined by the river bed’s gradient or by the velocity of the current.
  • Faster moving turbulent water typically contains greater concentrations of dissolved oxygen, which supports greater biodiversity than the slow-moving water of pools.
  • These distinctions form the basis for the division of rivers into upland and lowland rivers.
Marine ecosystems
  • Marine ecosystems cover approximately 71% of the Earth’s surface and contain approximately 97% of the planet’s water.
  • They generate 32% of the world’s net primary production.
  • They are distinguished from freshwater ecosystems by the presence of dissolved compounds, especially salts, in the water.
  • Approximately 85% of the dissolved materials in seawater are sodium and chlorine. Seawater has an average salinity of 35 parts per thousand (ppt) of water. Actual salinity varies among different marine ecosystems.
  • An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea.
  • Estuaries form a transition zone between river environments and maritime environments.
  • Estuaries are highly productive as compared to the adjacent river or sea.



  • The biosphere is the global sum of all ecosystems. The two joined words are “bio” and “sphere”. It can also be termed as the zone of life on Earth, a closed system, and largely self-regulating.
  • The biosphere is the global ecological system integrating all living beings and their relationships, including their interaction with the elements of the lithosphere, geosphere, hydrosphere, and atmosphere.
  • The biosphere is that area where all the other three spheres i.e. lithosphere, hydrosphere, and atmosphere meets
  • If we imagine an orange as earth, then its thin cover would be biosphere.
  • Life in the biosphere is abundant between 200 meters below the surface of the ocean and about 6,000 meters above sea level.
  • Biosphere is absent at extremes of the North and South poles, the highest mountains and deepest oceans since existing hostile conditions there do not support life.
  • Occasionally spores of fungi and bacteria do occur at a great height beyond 8,000 meters, but they are not metabolically active, and hence represent only dormant life.
  • The energy required for life within the biosphere comes from the sun. The nutrients necessary for living organisms come from air, water, and soil. The same chemicals are recycled over and over again for life to continue.
  • Living organisms are not uniformly distributed throughout the biosphere. Only a few organisms live in the polar regions, while the tropical rain forests have an exceedingly rich diversity of plants and animals.
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