Figure 1. Simplified food web with connections among trophic levels. Primary producers (bacteria, phytoplankton, algae, and seagrass) produce organic matter through photosynthesis. Primary consumers feed directly on bacteria and plants. Secondary consumers eat primary consumers, and, in turn, are eaten by tertiary consumers. In truth, trophic connections are often much more complex, with consumers feeding at several trophic levels.
Credit: Florida Sea Grant