The main ingredient in the oceans of the earth is water (just by a drop)

The oceans are crowded with little animals and plants most of them so tiny you will not see them with the naked eye. These creatures are the so called plankton the basis of every food chain in the seas.
Plankton is made up of four major kinds of life forms.

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  *Bacteria: single cellular creatures some with chlorophyl, some with wiptails, some with both
  
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  *Plants: tiny algae near the surface using light as power source.
  
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  *Animals: arthropods (joint legged) tiny creatures swimming in search for each other or algae and bacteria to eat
  
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  *Larvae: mostly jellyfish and larger arthropods (these are just temporary plankton)