POSSIBLE IMPACTS OF CO_2 STORAGE ON THE MARINE ENVIRONMENT

摘要

The marine environment is the major natural sink for carbon dioxide. Most of it is dissolved, chemically transformed to bicarbonate or assimilated by phytoplankton and stored as biomass, bicarbonate and carbonate. For a long time in human history the atmospheric, marine and terrestrial ecosystems were in equilibrium so that there was no enrichment in any of these global ecosystems. The anthropogenic emissions led to increased CO_2 levels within a relatively short time frame of about 200 years from about 280 ppm up to 370 ppm today. The increasing use of fossil fuels leads to an emission of about 23 Gt CO_2/y = 6 GT C/y. The marine environment is a strongly buffered and stable system so far. The net oceanic uptake is about 1.7 Gt C/y, the terrestrial about 1.4 Gt C/y and the atmospheric storage about 3.2 Gt C/y. This immense removal mechanism is based on the marine productivity ("Biological Pump") and on the global ocean circulation ("Solubility Pump"). The effectiveness of these processes relies among others on the marine constituents (e.g. nutrients, essential trace metals), the ecosystems and their diversity, the conditions (e.g. pH, temperature, pCO_2, salinity) and the well-working global pumping and circulation mechanisms. An increased uptake of CO_2 will change the pH of the marine system and that entails a number of other adverse effects which will change and threaten marine ecosystems concerned.