Final answer:
Aquatic photoautotrophs play a crucial role in the carbon cycle by absorbing atmospheric CO2 during photosynthesis, contributing to reduced CO2 levels in the atmosphere and affecting the oceanic carbon reservoir and the pH of water.
Step-by-step explanation:
The effect of aquatic photoautotrophs on the concentration of CO2 in the air is significant due to their role in the carbon cycle and photosynthesis. Aquatic photoautotrophs, like phytoplankton, absorb CO2 from the atmosphere during photosynthesis to produce oxygen and organic carbon.
This not only contributes to reducing atmospheric CO2 levels but also impacts the carbon reservoir in the oceans, which can affect CO2 exchange rates between the atmosphere and the ocean. The depletion of CO2 in water by these organisms can also affect the pH, impacting the metabolic processes of various marine life.
Moreover, as aquatic photoautotrophs require light to survive, anything that decreases light penetration, such as increased organic carbon from algal blooms, can hinder their growth, potentially disrupting the balance of oxygen and CO2 levels in aquatic environments.