Thursday, October 31, 2013

Aquatic ecosystem - Oceans

MARINE ECOSYSTEMS ((OCEANS)
Oceans cover more than two third of the earth's surface. Ocean environment is characterized by a high concentration of salts and minerals. It supplies a large variety of sea products and drugs. Among others, it is a reservoir of magnesium, iron, phosphorus and natural gas.

ZONES OF THE OCEAN
Oceans have two major life zones.
  1. Coastal zone which is relatively warm, nutrient rich and shallow water.It is the zone of high primary productivity because of high sunlight.
  2. Open sea is the deep part of the sea that is vertically divided into three regions.
      1. Euphotic zone that receives abundant light and shows high photosynthetic activity
      2. Bathyal zone that receives low light and is usually geologically active
      3. Abyssal zone which is dark and very deep (~2000 to 5000m)
CHARACTERISTICS OF OCEAN ECOSYSTEM
  1. It occupies a large surface area with saline water
  2. Commercial activities like fishing and shipping are carried-out in oceans
  3. It is rich in biodiversity
  4. It helps moderate the temperature of earth.
STRUCTURE AND FUNCTION OF OCEAN ECOSYSTEMS
Abiotic components
Ex: Temperature, Light, NaCl, K, Ca, and Mg salts, Alkalinity

Biotic components
  1.  Producers: Ex: Phytoplankton (diatoms, unicellular algae, etc) and marine plants (sea weeds, chlorophyceal, Phaeophycaea)
  2. Consumers: They are heterotrophic macroconsumers and depend on producers for their food.
        1. Primary consumers (herbivores) feed on producers. Ex: Crustaceans, molluscs, fish
        2. Secondary consumers (Carnivores) feed on herbivores. Ex: Herring, sahd, mackerel, etc
        3. Tertiary consumers are the top consumers. They feed on small fishes. Ex: Cod, Haddock, etc.
  3. Decomposers: They decompose dead organic matter. Ex: Bacteria and some fungi.

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