Controls of Primary Production
This chapter deals with selected variables (light, nutrients, and temperature) that function as proximate or immediate controls of abundance and activity of marine primary producers. Grazing and sinking, two other major proximate factors affecting producers, are discussed in Sects. 10.3 and 15.2.4. These proximate controls act to set rates, govern densities, sizes, and other responses by producers. Later chapters deal with driver variables (hydrodynamics, climate, weather, and geology) that act as the ultimate mechanisms that determine the conditions under which the action of proximate controls, and the responses of the producers and consumer organisms, take place. These linkages constitute the rather complicated matrix of interactions that generates the very varied features and conditions across environments. These interactions result in the complex set of controls of communities and ecosystems that will be the focus of later chapters.