How do phytoplankton impact surface water ecosystems?

Phytoplankton play a crucial role in surface water ecosystems primarily by serving as a fundamental food source for a variety of aquatic organisms. These microscopic plants are the base of the aquatic food web; they convert sunlight and nutrients into organic matter through photosynthesis, which is then consumed by small zooplankton, and in turn, larger fish and marine predators. The presence of phytoplankton supports not only the growth and health of these organisms but also contributes to the overall biodiversity and stability of the ecosystem. Their ability to produce oxygen as a byproduct of photosynthesis also supports aerobic organisms, but their primary significance arises from the energy they provide to higher trophic levels in the food chain.