Carbon dioxide can enter the water through multiple pathways. Some primary land sources can include decay of organic matter, dissolution of carbonate rocks, wastewater discharge, and watershed draining. Other natural sources include biological respiration, sediment diagenesis, or volcanic activity. A major source/sink of CO2 is atmospheric exchange at the air/water interface. Simply, carbon dioxide gas dissolves in water.
An increase in pCO2 concentrations in water causes a drop in pH. As many biological, chemical, and physical processes are pH dependant, sudden or rapid changes in pH may have adverse effects on the regulation of these processes. Along with pH effects, high levels of CO2 have been shown to be detrimental to the development of certain organisms such as finfish, shellfish and other calcifying organisms, including phytoplankton.