Key Functions of Ecosystem:-  

• Productivity
• Efficiency
• Energy flow
• Decomposition
• Recycling of material
• Develop and stabilization

Productivity:- It is rate of biomass production or solar energy captured per unit are per unit time.

Production can be expressed in g/m²lyr or Kcal/m²/yr:

Primary productivity:-

It is rate or amount of solar energy captured for formation of biomass by the process of photo synthesis. Per unit area per unit time.

Primary Productivity:-

1. Gross primary productivity (GPP):- It is total rate of Biomass production or solar energy captured or photosynthesis.
2. Net primary productivity (NPP):- The amount of Biomass stored in producer after respiratory loss.

GPP = NPP + R (Respiratory const.)

Sec. Productivity:- (sp)

The amount of biomass stored in producer which is for consumer level

SP = NPP – NP

Net Productivity:- (NP)

The amount of biomass stored in producer which is not for consumer level.  

NP = NPP – SP

• Max. Productivity on earth in coral reef.
• Max. productivity on  land in tropical rain forest.
• Min.  productivity on earth at desert and tundra.

Primary productivity is max. in tropical rain forest when proper moisture is available throughout the year.

In ocean usually light behave as limiting factor for photosynthesis. But in deep ocean nutrient mainly N₂ behave as limiting factor.

• 170 Billion tones Co₂ fixed annually by the process of photosynthesis on earth.

Ocean contribute 71% of total area of earth. But ocean fix only 55 Billion tone Co₂ annually  in photosynthesis, rest in land.