US EPA

92336 

Journal Article 

Eutrophication of Lake 227, Experimental Lakes Area, northwestern Ontario, by addition of phosphate and nitrate 

Schindler, DW; Armstrong, FAJ; Brunskill, GJ; Holmgren, SK 

1971 

Yes 

Journal of the Fisheries Research Board of Canada
ISSN: 0015-296X 

28 

11 

1763-1782 

10.1139/f71-261 

WOS:A1971L535200010 

http://www.nrcresearchpress.com/doi/abs/10.1139/f71-261
Exit
 

Addition of 0.34 g P as Na2HPO4 and 5.04 g N as NaNO3 per square meter to a small unproductive Canadian Shield lake over a period of 17 weeks caused a severalfold increase in phytoplankton standing crop, and a change in dominant species from Chrysophyceae to Chlorophyta. Reactive phosphate concentrations remained at undetectable levels in the epilimnion after fertilization, and inorganic nitrogen concentrations remained low. Most of the added phosphorus and nitrogen was rapidly taken up by phytoplankton and sedimented with the seston.Although concentrations of total CO2 decreased to less than 20 μmoles/liter and pH values increased to greater than 9 in late summer, a high standing crop of phytoplankton was maintained. No marked increase in the rate of phytoplankton production was noticed Experiments in polyethylene containers suspended in the lake during this period of low total CO2 indicated that carbon was not limiting to algal production, except possibly at algal standing crops in excess of 100 μg/liter chlorophyll a, and that phosphorus was the primary limiting nutrient.Sodium added with the nutrients remained in the epilimnion until fall overturn, indicating that very little of it was utilized by phytoplankton 

*EUTROPHICATION; *PHOSPHATES; *NITRATES; PHYTOPLANKTON; STANDING CROPS; CHRYSOPHYTA; CHLOROPHYTA; CARBON DIOXIDE; HYDROGEN ION CONCENTRATION; SODIUM; LIMITING FACTORS; *EXPERIMENTAL LAKES AREA(ONTARIO); LIMITING NUTRIENTS