Algal carbon uptake and the difference between alkalinity and high pH ("alkalization"), exemplified with a pH drift experiment
J. Uusitalo

Plant biologists sometimes seem to confuse, or fuse, alkalinity with alkalization, not only in a linguistic sense, but also as concepts. By using data from carbon uptake in three marine algae; one brown (Phaeophyta): Ascophyllum nodosum (Fucales), one green (Chlorophyta): Ulva lactuca (Ulvales) and one red (Rhodophyta): Polysiphonia nigrescens (Gigartinales), the difference between the concepts of "alkalization", i.e. pH-increase, and changes in alkalinity is demonstrated. In a pH-drift experiment A. nodosum was able to take up carbon, while remaining at the same pH (i.e. no "alkalization"), due to lowered alkalinity caused by proton excretion. U. 1actuca did not change alkalinity while taking up carbon and consequently showed the expected pH increase, an effect of the carbon uptake. P. nigrescens released carbon while remaining at the same pH, the latter being a consequence of increased alkalinity. The concept of alkalinity is discussed and the author suggests that care should be taken by plant biologists to define terms used in regard to what is measured.

Keywords: Ascophyllum nodosum (Phaeophyta), Ulva lactuca (Chlorophyta), Polysiphonia nigrescens (Rhodophyta).
Contents of this volume Sci. Mar. 60(Suppl.1) : 129-134 Back PDF
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