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Bicarbonate transport and extracellular carbonic anhydrase activity in Bering Sea phytoplankton assemblages: Results from isotope disequilibrium experiments
Author(s) -
Martin Cheryl L.,
Tortell Philippe D.
Publication year - 2006
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.2006.51.5.2111
Subject(s) - phytoplankton , oceanography , extracellular , stable isotope ratio , bicarbonate , carbonic anhydrase , environmental chemistry , chemistry , biomass (ecology) , environmental science , ecology , biology , nutrient , geology , biochemistry , enzyme , organic chemistry , physics , quantum mechanics
We used a 14 C isotope disequilibrium technique to provide quantitative estimates of both direct HCO 3 ‐ transport and extracellular CA activity in Bering Sea phytoplankton assemblages. The method revealed that direct HCO 3 ‐ transport was the dominant mechanism of inorganic C uptake in both coastal and open ocean waters, accounting for more than half of the total C flux to the phytoplankton. The relative importance of HCO 3 ‐ transport was not related to phytoplankton biomass, productivity, or ambient CO 2 concentrations at individual sampling stations. However, HCO 3 ‐ transport and total inorganic C uptake rates decreased in response to elevated CO 2 in direct manipulation experiments. Kinetic analysis of the 14 C time‐course data revealed low levels of extracellular carbonic anhydrase activity at most stations. This activity was related to phytoplankton taxonomic compositions and/or CO 2 concentrations, but was relatively unaffected by direct CO 2 manipulations.