Question

Explain primary productivity and the factors that influence it.

Answer 1

Primary productivity is used to describe the rate at which plants and other photosynthetic organisms produce organic compounds or organic matter or biomass in an ecosystem.

Primary productivity has two aspects :

• Gross productivity = the entire photosynthetic production of organic matter during photosynthesis in an ecosystem.

• Net productivity = the organic materials that remain after respiration loses incurred in photosynthetic organisms in the ecosystem or in simple words it is defined as gross primary productivity minus respiratory losses

NPP= GPP- R ( Respiration loss)

Since oxygen is one of the most easily measured products of both photosynthesis and respiration, a good way to measure primary productivity in an aquatic ecosystem is to measure dissolved oxygen.

Gross productivity cannot be directly measured because respiration is always occurring simultaneously with photosynthesis that involves use of oxygen and organic compounds.

Factors that influence primary productivity are:-

1. Light: The light field varies with depth in the ocean, with time of day, and with time of year.

Primary production in the ocean exhibits a strong depth dependence and a strong time dependence.

2. Temperature: Temperature controls the enzyme-mediated dark-reaction rates of photosynthesis.

3. Species composition also influence rates of primary production. For example, the size distribution of the cells and the pigment composition of the cells can both change with species composition, thus influencing nutrient uptake and light absorption for photosynthesis.

4. Availability of nutrients and photosynthetic capacity of plant also influence the primary productivity.

5. Species succession is also a determining factor.