Impact of CO2 on Photosynthesis

A team of scientists performed a study to assess the impact of different levels of CO₂ concentration on the rate of photosynthesis in aquatic plants. They set up three tanks with varying CO₂ levels: low (100 ppm), medium (400 ppm), and high (1000 ppm). Over a four-week period, they measured the rate of oxygen production in each tank as an indicator of photosynthesis. The following results were recorded:

• Low CO₂: 2 mg O₂/L/hour
• Medium CO₂: 6 mg O₂/L/hour
• High CO₂: 8 mg O₂/L/hour

From these results, what can be concluded about the effect of CO₂ concentration on the rate of photosynthesis in the aquatic plants studied?