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EXOGENOUS SOURCES OF INORGANIC CARBON FOR PHOTOSYNTHESIS BY MARINE MACROALGAE 1
Author(s) -
Maberly Stephen C.
Publication year - 1990
Publication title -
journal of phycology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.85
H-Index - 127
eISSN - 1529-8817
pISSN - 0022-3646
DOI - 10.1111/j.0022-3646.1990.00439.x
Subject(s) - chlorophyta , total inorganic carbon , biology , carbon fibers , photosynthesis , seawater , algae , botany , environmental chemistry , marine species , carbon dioxide , ecology , chemistry , materials science , composite number , composite material
Thirty‐five species of marine macroalgae were tested for their ability to remove inorganic carbon from seawater using the pH‐drift technique. Six of these species, all Rhodophyta, were unable to use HCO 3 – . The remaining species exhibited a range in ability to use HCO 3 – and deplete inorganic carbon (C τ ); the three most effective species, all Chlorophyta, raised the pH to over 10.50, depleted the concentration of CO 2 effectively to zero, and depleted the concentration of C τ to less than 50% of that at air‐equilibrium. In contrast, the six species restricted to CO 2 did not raise the pH above 9.0 at a CO 2 concentration of about 1.5 μmol · L ‐1 and depleted the concentration of C τ to about 80% of that at air‐equilibrium. Ability to raise pH and deplete C τ was linked to the habitat in which the species grew. Five of the six species which lack the ability to use HCO 3 – grow subtidally in relatively low light beneath a canopy of larger Phaeophyta. None of these species grow in rockpools where carbon‐depletion may occur. Species from rockpools were all effective at removing inorganic carbon. Competition for C τ may be one of the factors that determines species composition in rockpools. There was a species‐specific difference between the calculated concentration of C τ at the end of a pH‐drift experiment and that measured directly. Most, but not all, species with the ability to generate high pH‐values showed a lower than calculated final concentration of C τ consistent with precipitation of CaCO 3 . A number of Rhodophyta with no, or a limited, ability to use HCO 3 – showed the opposite response, with final concentrations of C τ exceeding that calculated from the pH. Calculations based on the maximum gross rate of production of CO 2 from HCO 3 – in the absence of external carbonic anhydrase confirmed the results of the pH‐drift experiments by demonstrating HCO 3 – ‐use in Monostroma fuscum (Post et Rupr.) Wittr. And Ulva lactuca L. and the lack of this ability in Lomentaria articulate (Huds.) Lyngb. Rates of net photosynthesis at air‐equilibrium were greater than 95% of those at 2.3 mmol C τ · L ‐1 for many of the species which were able to use HCO 3 – , but on average only 72% for the six species restricted to CO 2 .