Unlike land plants, photosynthesis in many aquatic plants relies on bicarbonate in addition to CO2 to compensate for the low availability of CO2 in water.
Unlike land plants, photosynthesis in many aquatic plants relies on bicarbonate in addition to CO2 to compensate for the low availability of CO2 in water. A study in the scientific journal SCIENCE by Iversen and co-authors shows that the abundance of plant species with the ability to use bicarbonate increases in hard water lakes with greater bicarbonate concentrations. In streams, where the CO2 concentration is higher than in air, bicarbonate users are few.
Globally, photosynthetic modes of terrestrial plants are influenced by climatic factors such as adaptations to variation in air temperature and water availability. In water, CO2 often limits photosynthesis because it moves 10,000-times slower than in air and, thus, rapid photosynthesis can deplete CO2 in dense plant stands. In order to meet the requirements of water plants, CO2 concentrations must be 10-20 times higher than in air. This never happens in lakes, where microscopic algae may reduce the CO2 content to 10% of that in air.
The solution among many water plants is to use bicarbonate, which is dissolved in high concentrations in lakes located in calcareous catchments.
Read more at: Faculty of Science - University of Copenhagen