||Environmental Control of Nitrogen Fixation in Lakes: I. In situ Nitrogen Fixation by Free Living Blue-Green Algae. II. Nitrogen Fixation by the Duck-Weed-Algal Association.
Tiedje, J. M. ;
Cichowski., Mark ;
||Michigan State Univ., East Lansing. Inst. of Water Research.
||DI-14-31-0001-3222; OWRR-A-046-MICH; W74-07716 ; OWRR-A-046-MICH(1)
Nitrogen fixation ;
Aquatic weeds ;
Wintergreen Lake ;
Plant growth ;
Nitrogen cycle ;
Biochemical cycles ;
Algal blooms ;
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In situ acetylene reduction studies in hypereutrophic Wintergreen Lake showed that nitrogen fixation occurred from early July until mid-August and was correlated with the presence of heterocyst-bearing blue-green algae. Aphanizomenon was the dominant nitrogen fixing organism in 1970 while Anabaena was dominant in 1971; the Anabaena bloom resulted in 10 times more fixation than the Aphanizomenon bloom. Significant acetylene reduction was limited to the euphotic zone (0-3 m). The duckweeds Lemna and Spirodela were found to have a commensalistic relationship with blue-green algae that resulted in significant nitrogen fixation. Acetylene reduction by this association was widespread as it occurred in 27 of 30 sample sites over three years (1971-1973). The quantitites of nitrogen fixed could represent major sources of nitrogen particularly for shallow and/or intermittent bodies of water.