New Zealand Journal of Marine and Freshwater Research abstracts

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Macronutrient controls on nitrogen fixation in planktonic cyanobacterial populations

ALEXANDER J. HORNE¹

MARCIE L. COMMINS²

¹Department of Civil Engineering and Sanitary Engineering and Environmental Health Research Laboratory
University of California, Berkeley California 94720, U.S.A.

²Department of Zoology University of California, Davis California 95616, U.S.A.

Abstract Experiments described in the literature have demonstrated that additions of N, Fe, and occasionally P, influence planktonic cyanobacterial nitrogen fixation in lakes and estuaries throughout the world. Increase in abundance of cyanobacteria which can fix nitrogen did not necessarily indicate that N₂ fixation had occurred. In natural plankton assemblages, N₂ fixation was normally stimulated by low total inorganic nitrogen (TIN) and depressed by additions of TIN. Nitro-genase was often stimulated by addition of Fe but soluble reactive phosphate (SRP) alone only stimulated nitrogenase activity occasionally. Luxury consumption and storage of P, but not N, explains the lack of P stimulation in nature. Nitrogenase activity was usually repressed at TIN concentrations of >50-100 tig 1-'. Additions of N + P had variable effects which may depend on the balance between nitrogenase inhibition by N and general growth stimulation by N + P (which reduces ambient N).

Keywords blue-green algae; cyanobacteria; estuaries; iron; lakes; macronutrients; nitrogen fixation; nitrogenase regulation; phosphorus; plankton

New Zealand Journal of Marine and Freshwater Research, 1987, Vol. 21: 413-423 0028-8330/87/2103-0413$2.50/0 © Crown copyright 1987 Received 19 February 1987; accepted 18 May 1987

PDF file of entire paper: medium quality (1260K); (scanned from paper original: notes about this process)

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