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

Abstract

Cyanobacteria are the only group of phytoplankton to show a clear increase both in biomass 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 l -1 or spring total phosphorus (TP) concentrations of 25-30 μg l -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.

Nitrogen, phosphorus, and nitrogen fixation in lacustrine and estuarine ecosystems

“…It is consistent with the empirical analysis of Toetz and McFarland (1987), however, and with the conclusions of other investigators who have suggested that absolute P concentrations rather than N : P ratios may be the dominant factor influencing the success of planktonic cyanobacteria (e.g. Doremus 1982;Reynolds 1986;Pick and Lean 1987;Trimbee and Prepas 1987;Garnier and Montesanto 1988;Shapiro in press).…”

“…Moreover, several studies (e.g. Healey 1982;Pick and Lean 1987;Paerl 1988bPaerl , 1990) have suggested that low N : P need not necessarily result in dominance by heterocystous cyanobacteria in lakes, and Howarth et al (1988b) found no relationship between N : P loading ratios and the proportion of cyanobacteria in estuarine phytoplankton. Consistent evidence for an effect of N : P loading ratios on N fixation is thus lacking.…”

The low TN:TP ratio, a cause or a result of Microcystis blooms?

“…Some researchers [14,15] have recognized that even when such a response is observed, it may be due to the increasing P concentrations rather than a decrease in the N:P ratio. Neither laboratory nor whole-lake studies provide conclusive evidences that N:P plays a major role in cyanobacterial dominance [16]. Thus, well-designed experimental works are needed to resolve this perplexing problem.…”

Blooming algae: a Canadian perspective on the rise of toxic cyanobacteria

“…Several review articles have been published outlining the reasons for the dominance (Pick and Lean 1987;Paerl 1988); this continues to be an active area of research, with Canadian researchers contributing novel explanations and interpretation (Molot et al 2014;Taranu et al 2012), as well as novel approaches from paleolimnology (Taranu et al 2015) and molecular biology (Fortin et al 2010). In many ecological studies, cyanobacteria tend to be examined as one functional group when there is considerable functional diversity among bloom-forming taxa.…”