In the depicted food chain, the phytoplankton serves as the primary producer, being consumed by zooplankton, which, in turn, is preyed upon by small fish, illustrating a clear trophic relationship within the aquatic ecosystem.
Within the food web illustrated in Figure 3-4, a distinct feeding relationship unfolds in a specific food chain. The foundational link is established by phytoplankton, microscopic photosynthetic organisms that act as primary producers by converting sunlight into energy.
Zooplankton, small animal-like organisms, form the next trophic level as primary consumers, relying on phytoplankton as their primary food source. Subsequently, small fish occupy the following trophic level, preying upon zooplankton for sustenance. This sequence exemplifies the interconnected nature of ecosystems, emphasizing the transfer of energy through trophic levels and highlighting the dependence of each organism on the lower levels for their nutritional needs.