Answer:
Gross productivity refers to the amount of carbon fixed.
Step-by-step explanation:
Gross productivity refers to the amount of carbon fixed during the process of photosynthesis by all producers such as plants and algae etc in the ecosystem. A large part of the energy that is produced in the process of photosynthesis is used by the plants in the metabolic processes of the producers such as respiration. The net productivity indicates that carbon dioxide plants that is used during the photosynthesis process substracted from carbon dioxide the plants releases during the process of respiration.