Sunlight plays a crucial role in the ecosystem of a lake or pond. The depth of the water body determines how much sunlight reaches the bottom. Ponds are typically shallow enough to allow sunlight to penetrate the entire water body, supporting a consistent ecosystem with rooted plants, pond weeds, algae, and phytoplankton. In contrast, lakes are usually much deeper, and sunlight cannot reach the bottom in most places, creating an aphotic zone where no plants, phytoplankton, or algae grow. This makes the lake ecosystem very different from ponds, as the aphotic areas are populated solely by carnivorous organisms. The effect of sunlight on a lake or pond determines the type of aquatic life that can thrive in the water body.