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Potentiometric measurements of carbon dioxide flux of submerged aquatic macrophytes in pH‐statted natural waters
Author(s) -
DENNY PATRICK,
ORR PHILIP T.,
CSIRO DAVID J. C. ERSKINE
Publication year - 1983
Publication title -
freshwater biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.297
H-Index - 156
eISSN - 1365-2427
pISSN - 0046-5070
DOI - 10.1111/j.1365-2427.1983.tb00010.x
Subject(s) - alkalinity , titration , carbon dioxide , total inorganic carbon , potentiometric titration , cuvette , chemistry , seawater , dissolved organic carbon , macrophyte , environmental chemistry , photosynthesis , gran plot , volume (thermodynamics) , titration curve , inorganic chemistry , ecology , electrode , biochemistry , physics , organic chemistry , quantum mechanics , biology
SUMMARY. 1, An apparatus has been described that is suitable for potentiometric measurement of carbon dioxide flux in photosynthesizing shoots of submerged aquatic macrophytes 2. The procedure, based on methods described by Tailing (1973) for measurement of phytoplankton photosynthesis, relies upon the continuous pH‐statting of the solution surrounding the tissues. The pH of the solution is monitored by electrodes from a pH meter which is linked to an auto‐titrator. The rise in pH during photosynthesis is then compensated tor by controlled, small titrant additions of CO 2 ‐ennched solution (titrant water). This replaces the CO 2 removed by the tissues without affecting the total alkalinity of the solution. If the concentration of CO 2 in the titrant water, and the volume of titrant added arc known precisely, the CO 2 flux can be calculated. 3. Total alkalinity, total CO 2 and free‐CO 2 acidity of the bathing solutions and titrant waters are estimated by Gran titrations and the pH: tilre‐volume data pairs are analysed by computer to provide rapid data feed‐back. A modification to Tailing's equation for calculation of F 1 functions has been necessary for accurate calibration of the CO 2 enriched tilrant water. 4. The photosynthesis cuvette, which is surrounded by a water‐jacket, is approximately I dm 3 in capacity and has six compartments for the shoots. An impeller at the base of the cuvette rapidly mixes and cycles the bathing solution and flushes it over the tissues. 5. Information on temperature, light flux density, oxygen concentration. pH and titre‐volume is continuously recorded into a data‐logger and is fed into a computer which is programmed for data analyses. 6. Results from a typical experiment show the system to be sound and the method has considerable potential, especially in the study of aquatic plant photosynthesis in natural waters.