The carbon cycle, alkalinity, and liming

Primary production on land is fueled by a constant (400 ppm in 2015) supply of CO₂. One of the most important principles of limnology, however, is that dissolved CO₂ levels in water are variable. Not only does the supply of CO₂ vary greatly during the diurnal cycle as it is depleted by photosynthesis and replenished by respiration, but the total amount of CO₂ available to participate in the diurnal cycle varies from water body to water body. This variability is of fundamental concern to the study of static water fish culture because low availability of CO₂ in water may limit primary productivity and hence, fish production. Management in the form of addition of agricultural limestone is then needed to supply the necessary CO₂ to fuel photosynthesis at a satisfactory level.