Effect of Nitrogen and Phosphorus on Growth of Toxic and Nontoxic Microcystis Strains and on Intracellular Microcystin Concentrations

Abstract

The growth and intracellular microcystin concentration of two hepatotoxic and two nontoxic axenic Microcystis strains were measured in batch cultures with variable nitrogen (0.84-84 mg L(-1)) and phosphorus (0.05-5.5 mg L(-1)) concentrations. Growth was estimated by measuring dry weight, optical density, chlorophyll a, and cellular protein concentration. Microcystin concentrations in cells and in culture medium were measured by HPLC analysis. Both nontoxic strains needed less nutrients for their growth at low nutrient concentrations. With high nutrient concentrations the toxic strains grew better than the nontoxic strains. Growth and intracellular microcystin concentration did not correlate in the hepatotoxic strains. Multivariate regression analysis together with mathematical modeling revealed a significant interactive effect of nitrogen and phosphorus, which partly explains the controversial results obtained in previous studies. In this study we have shown that variation of nitrogen and phosphorus concentrations influence the growth and the microcystin production of Microcystis strains and that the strains differ in their response to nutrients. High levels of nitrogen and phosphorus in freshwaters may favor the growth of toxic Microcystis strains over nontoxic ones.

Seasonal Dynamics of Microcystins with Associated Biotic and Abiotic Parameters in Two Bays of Lake Taihu, the Third Largest Freshwater Lake in China

“…Similar results were also found in Lake Ringsjön, southern Sweden (Gertrud et al 1999). On the other hand, some studies indicate positive relation between trophic status and MC production (Vézie et al 2002). In the present study, MC production was dependent on the growth of Microcysts because of the positive linear correlation between intracellular MC content and Microcystis biomass in both bays.…”

“…The negative linear correlations between MC and N concentrations indicate that N is a regulating factor for MC production in Lake Taihu. This disagrees with the view that high nitrogen level enhances MC production of Microcystis (Vézie et al 2002;Downing et al 2005). Previous studies about this were quite contradictory: in some studies, MC concentration was positively correlated with TN (Lahti et al 1997) and NO 3 -N (Vézie et al 1997), but in other cases, it was negatively correlated with NO 3 -N (Lahti et al 1997).…”

“…External nutrient concentrations are suggested as an important factor for different toxicity of water blooms (Rapala and Sivonen 1998). There have been extensive laboratory studies to evaluate effects of environmental factors on MC production, such as the incidence of light on MC biosynthesis (Hesse and Kohl 2001), the response of MC-producer strains at different temperatures (Sivonen and Jones 1999;María et al 2003), and the production of MC under different nutrient limitation, mainly P and N restriction (Oh et al 2000;Hesse and Kohl 2001;Long et al 2001;Vézie et al 2002;María et al 2003). However, some of these results are contradictory.…”

Nutrients drive transcriptional changes that maintain metabolic homeostasis but alter genome architecture in Microcystis

“…This paradigm has begun to shift in recent years, however, to recognize a potential role for nitrogen (N) concentrations and chemical forms in driving bloom formation and biological community structure (Dolman et al, 2012). Although this shift remains hotly debated (Downing et al, 2001;Scott and McCarthy, 2010;Paerl et al, 2011;Paterson et al, 2011), it is clear that Microcystis exhibits a differential response when exposed to various N-containing chemical species (Donald et al, 2011) and concentrations (Vézie et al, 2002), as well as various P concentrations both in the environment (Wilhelm et al, 2003;Davis et al, 2010) and in culture (Shen and Song, 2007;Harke et al, 2012). Specifically, urea appears to stimulate rapid biomass accumulation of Microcystis when it enters fresh water as fertilizer runoff (Dolman et al, 2012).…”

Factors Shaping the Pattern of Seasonal Variations of Microcystins in Lake Xingyun, a Subtropical Plateau Lake in China

“…Laboratory studies indicate that production of microcystin by Microcystis is affected by various environmental factors such as light, temperature, nutrients, trace elements, salinity, pH and nutrient contents in cells (Gorham 1964;Van der Westhuizen and Eloff 1985;Watanabe and Oishi 1985;Oh et al 2000;Lee et al 2000;Long et al 2001). Environmental variables are likely to influence MC concentration directly by influencing cellular microcystin production and content (Orr and Jones 1998;Long et al 2001), and indirectly by influencing cyanobacterial species and strain composition (Chorus 2001;Vézie et al 2002).…”