New Zealand Journal of Marine and Freshwater Research abstracts

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The role of macronutrients (C, N, P) in controlling cyanobacterial dominance in temperate lakes

FRANCES R. PICK¹

DAVID R. S. LEAN²

¹Department of Biology Ottawa University Ottawa, Ontario Canada KIN 6N5

²National Water Research Institute Box 5050, Burlington, Ontario Canada L7R 4A6

Abstract Cyanobacteria are the only group of phytoplankton to show a clear increase both in bio-mass and relative contribution to total phytoplankton biomass as temperate lakes become eutrophic. Correlative studies indicate that this increase begins at total phytoplankton biomass levels of 3-5 mg fresh weight I"¹ or spring total phosphorus (TP) concentrations of 25-30 ng I"¹. Above TN: TP ratios of 30, cyanobacteria tend to become rare, but below this value they may or may not dominate. Better predictions may be possible by attempting to remove the influence of the refractory dissolved organic nitrogen and phosphorus fractions by using the TN-DON: TP-DOP ratio. While experimental manipulation of N : P ratios in enclosures or entire lakes may often stimulate or suppress relative cyanobacterial biomass, laboratory studies do not clearly link low N : P ratios with cyanobacteria. Evidence from correlative studies, long-term records of individual lakes, and experimental manipulations of nutrient loads suggest that other factors such as temperature, mixing regimes, transparency, and iron or carbon availability may influence cyanobacterial dominance in lakes.

Keywords blue-green algae; carbon; cyanobacteria; dominance; eutrophication; nitrogen; phosphorus; temperate lakes; total nitrogen to phosphorus ratios

New Zealand Journal of Marine and Freshwater Research, 1987, Vol. 21 ■ 425-434 0028-8330/87/2103-0425$2.50/0 © Crown copyright 1987 Received 19 February 1987; accepted 15 June 1987

PDF file of entire paper: medium quality (965K); (scanned from paper original: notes about this process)

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