Why are plants in deep freshwater lakes limited to the photic zone?

In deep freshwater lakes, plants are limited to the photic zone—also known as the trophogenic zone—because this is the only region where sufficient sunlight penetrates to support photosynthesis.1

Within this upper layer, the production of biochemical energy through photosynthesis exceeds the energy consumed by respiration and decomposition. Conversely, in the deeper aphotic zone (or tropholytic zone), light levels are insufficient for photosynthesis, meaning that the consumption of energy by organisms exceeds its production. The boundary between these two zones is defined by a plane of compensation, where the rates of primary production and consumption are equivalent. Because plants rely on light to synthesize the energy required for their survival and growth, they cannot inhabit the deeper, perpetually dark waters of a lake.1