Question

For a stable lake ecosystem, the net primary production (NPP) 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

The correct option is B Phytoplankton consumed by heterotrophs

Net Primary Productivity (NPP) is the amount of carbon uptake after subtracting Plant Respiration (RES) from Gross Primary Productivity (GPP). NPP is not equal to the total biomass of producers, but to the amount of biomass that is added. In a stable lake, the added phytoplankton biomass will equal that consumed by zooplankton.

Therefore, the correct answer is option B.