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Nitrogen fixation in Lake Mendota, Madison, Wisconsin 1
Author(s) -
Torrey Marguerite Sherman,
Lee G. F.
Publication year - 1976
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.1976.21.3.0365
Subject(s) - nitrogen fixation , heterocyst , algae , nitrogen , photosynthesis , cyanobacteria , phytoplankton , botany , biology , environmental chemistry , nitrogenase , ecology , chemistry , nutrient , bacteria , genetics , organic chemistry
The effects of various environmental conditions, and of cell composition, heterocyst content, and nitrogen content of algal samples, on fixation of N 2 by colonial and filamentous algae in Lake Mendota were investigated. Heterocyst content and temperature were significantly and positively related to acetylene reduction activity (N 2 fixation); depth of sample collection was negatively related. Available data do not show whether statistical correlations of acetylene reduction activity with dissolved O 2 and pH represent specific effects of O 2 and pH on this activity, or simply reflect chemical changes caused by algal photosynthesis. During summer stratification, when surface‐water content of combined inorganic nitrogen was severely depleted, N 2 fixation associated with heterocystous blue‐green algae contributed 85% of the total N 2 fixed. Bacterial N 2 fixation was low compared to that of algae. Despite its small overall contribution to the annual nitrogen budget (38,000 kg of nitrogen; ca. 7% of the total input), N 2 fixation is significant in maintaining blue‐green algal nuisances in surface water when non‐N 2 ‐fixing phytoplankton cannot compete effectively.