Question

A stable lake ecosystem shows net primary production which is equal to the

• A. Phytoplankton present in the photic zone
• B. Phytoplankton consumed by heterotrophs
• C. Dissolved nutrients used by phytoplankton
• D. Dissolved oxygen used by phytoplankton
• E. Dissolved oxygen used by all consumers

Answer 1

Answer: (B)

Phytoplankton consumed by heterotrophs

Phytoplankton are the primary producers of stable lake ecosystem and total phytoplankton present in photic zone represent the gross primary production i.e. total organic matter produced per unit area. Phytoplanktons consumed by heterotrophs represent net primary production which is calculated by the difference between gross primary production and organic matter consumed in respiration. Dissolved oxygen is not representative of primary productivity. Thus, the correct answer is B.