Which factor is NOT considered a bottom-up control of primary production?

Bottom-up controls of primary production refer to factors that influence the abundance and productivity of primary producers, such as plants and phytoplankton, primarily through resource supply. This means that the availability of essential resources such as nutrients, light, and temperature can dictate how much primary production occurs in an ecosystem.

Nutrients are vital for the growth of primary producers, as they provide the necessary elements for processes like photosynthesis. Light availability plays a significant role as well, since without sufficient sunlight, photosynthesis cannot occur effectively. Temperature can also affect the metabolism and growth rates of these producers, impacting their overall productivity.

Predation, on the other hand, is considered a top-down control. It refers to the activities of consumers at higher trophic levels that can regulate the population sizes of primary producers by consuming them. While predation can have significant effects on ecosystems, it does not directly influence the availability of resources like nutrients, light, or temperature, which are foundational elements that support primary production. Thus, it is the factor that is not part of bottom-up control.