NITROGEN-FIXATION BY EPILITHIC PERIPHYTON IN SMALL ARCTIC LAKES IN RESPONSE TO EXPERIMENTAL NITROGEN AND PHOSPHORUS FERTILIZATION

In 4 small arctic lakes located at Saqvaqjuac, NWT, epilithic periphyton in 0-2 m water depth were capable of fixing up to 0.86 mg N.m-2.h-1 during the period of active N-fixation from July to September 1981. Far Lake was fertilized with P for 3 yr and had a higher rate of fixation than did a P- and N-fertilized lake or a control lake. A numerical model based on incoming light was used to predict the amount of nitrogen fixed in each study lake throughout the season. The contribution of periphyton to the overall N budget for 1981 was 5% for the P- and N-fertilized lake, 16% for the control lake and 28% for the P-only fertilized lake. -from Authors