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Nitrogen fixation associated with the marine macroalga Codium fragile 1
Author(s) -
Head William D.,
Carpenter Edward J.
Publication year - 1975
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.1975.20.5.0815
Subject(s) - nitrogen fixation , biology , botany , seawater , nitrogen , nitrogenase , azotobacter , bacteria , ecology , chemistry , organic chemistry , genetics
Nitrogen fixation at rates of up to 7.3 µ g N 2 fixed g dry wt −1 h −1 is associated with the marine macroalga Codium fragile. A bacterium, identified as an Azotobacter, isolated from Codium, is capable of fixing atmospheric nitrogen in pure culture under aerobic conditions. Scanning electron micrographs showed dense populations of rod‐shaped bacteria, presumed to be Azotobacter, on the surface of Codium. When Codium photosynthesis is decreased by light shading, N 2 fixation drops proportionally, suggesting that fixation is coupled to the release of dissolved compounds by Codium. Addition of glucose to seawater increases N 2 fixation, indicating that the agent of fixation is a heterotroph. In a field survey, an inverse relationship was found between N 2 fixation and the concentration of combined N compounds in seawater. At total available N (NO 2 − , NO 3 − , NH 4 + , urea) concentrations greater than 10 µ g‐atoms liter −1 , no fixation was associated with Codium. At Nobska Beach the total nitrogen input through N 2 fixation in summer was 2.0 mg m −2 day −1 for water columns ranging between 1 and 3 m, and 0.47 in the 3–5‐m stratum.