Oceans cover approximately 70 per cent of the earth's surface. Major oceans of the world are Atlantic, Pacific, Indian, Arctic and Antarctic.
1. An ocean is a huge pool of salty water that extends over almost an infinite large area.
2. Ecosystem of an ocean is very stable and naturally well balanced.
3. They have high concentration of salts. It is about 3.5 per cent.
4. There is abundance of minerals such Na, CI, Ca, S, Mg etc.
5. Salinity is less near the north & south poles.
6. Salinity is more in deeper regions of the ocean.
7. This type of ecosystem plays an important role in regulating many biogeochemical cycles.
8. Oceans are the major sinks of C02 and play an important role in biogeochemical cycle.
9. The oceans have two major life zones.
1. Coastal Zone:
With relatively warm, nutrient rich shallow water. Due to high nutrients and ample sunlight this is the zone of high primary productivity.
2. Open Sea:
It is the deeper part of the ocean, away from the continental shelf. It is vertically divided into three regions:
(i) Euphatic Zone, which receives abundant light and shows high photosynthetic activity
(ii) Bathyal zone receives dim light and is usually geologically active.
(iii) Abyssal zone is the dark zone 2000 to 5000 meter deep. It has no sunlight. • It is the largest ecological unit but it is an incomplete ecosystem. Various components of the ocean ecosystem are as follows:
It is more stable in chemical composition due to being saline and moreover other physio- chemical factors such as dissolved oxygen content, light and temperature are also different. Marine water contains NaCl, Ca, Mg and K salts. Water is strongly buffered.
These are autotrophs. They are mainly phytoplanktons such as diatoms and some microscopic algae, seaweeds etc.
These all are heterotrophic macro-consumers. They depend for their nutrition on the primary producers. These are:
(a) Primary consumers:
They are herbivores and feed directly on producers, e.g., molluscs, crustaceans etc.
(b) Secondary consumers:
These are carnivorous fishes as Shad, Herring etc.
(c) Tertiary consumers:
They feed on other carnivores of the secondary consumers level. These are the top carnivores in the food chain, e.g., Cod, Haddock, and Halibut etc.
The microbes active in the decay of dead organic matter of producers and Macroconsumers are chiefly bacteria and some fungi.