Diversity and nitrogen-fixing activity of cyanoprokaryotes in the sphagnum cover of swamps in northeast European Russia

New knowledge has been obtained about the diversity and functional characteristics of cyanoprokaryotes associated with sphagnum mosses in bog complexes of the boreal zone of the European North and the Subpolar Urals. 19 species of diazotrophic cyanoprokaryotes were identified. The quantitative characteristics of nitrogen-fixing cyanoprokaryotes in epiphytic groups of sphagnum mosses and their seasonal changes were studied. It was revealed that Nostoc paludosum, N. punctiforme, Microchaete tenera form the basis of the dominant complexes of cyanoprokaryotes, actively fixing nitrogen in the studied communities. It was shown that N2 fixation in communities of the same type in the studied geographic regions had similar values. For a floodplain bog in the taiga zone, seasonal measurements of N2 fixation and quantitative indicators of cyanoprokaryotes associated with the sphagnum mosses Sphagnum riparium and S. angustifolium were carried out. N2 fixation in the season was more dependent on temperature conditions. On average, from 1.2 to 12.3 thousand colonies of nitrogen-fixing cyanoprokaryotes were recorded per 1 cm2 of sphagnum moss sod. The maximum values of the rates of N2 fixation, measured by the method of acetylene reduction, were noted in the range of 0.55–3.59 mg C2H4 m–2h–1. The maximum values of seasonal N2 fixations were 3,5 g C2H4 m–2 for S. angustifolium and 4,6 g C2H4 m–2 for S. riparium.

Growth of Sphagnum riparium is strongly rhythmic: Contribution of the seasonal, circalunar and third rhythmic components

Continuous high-resolution monitoring of Sphagnum growth can provide insights into the biological rhythms of moss growth. Moss Sphagnum riparium is a convenient model for growth monitoring. Application of the method of geotropic curvatures has enabled a three-year monitoring with two to five-day intervals. We measured the increment in ca. 85000 shoots and produced ca. 3500 growth rate estimates, making this study a champion in precision compared to previous efforts. The zeitgeber for seasonal growth rhythms is the temperature seasonal cycle (R2=0.21–0.52). When the temperature changes by 10°C, moss growth rate is modified by 0.10–0.17cm/day according to the linear model, and 1.47–2.06-fold in the exponential model. The zeitgeber for circalunar rhythms is the lunar synodic cycle (R2=0.14–0.26). The average amplitude of the fluctuations it induces in the growth rate is 0.0425– 0.0572cm/day, which is equivalent to the effect of a 3.43–4.53°C change in temperature. The third rhythm can be distinguished in periodograms. Its period ranges from 10 to 16 days, but we did not detect the zeitgeber.In total, three rhythms explain 51–78% of the growth rate. We believe that the strong rhythmicity in Sphagnum growth is associated with shoot growth synchronization.

Ecological tolerance and niche structure of Sphagnum along a pollution gradient near Sudbury, Ontario, Canada

Accumulations of Cu and Ni were measured in four Sphagnum species occupying overlapping niches at varying distances from the smelter at Falconbridge, Ont. A distinct relationship existed between the metal content of Sphagnum russowii and the reciprocal of the distance from the pollution source. Accumulations of Cu and Ni in the partially humidified peat subtending the living Sphagnum were significantly higher than the concentrations retained in the moss plants, particularly on sites having high metal loadings. Concentrations of Cu and Ni were not significantly different between species occupying overlapping height and pH zonations. There existed a significant relationship between metal accumulations in the capitula of Sphagnum russowii, Sphagnum magellanicum, and Sphagnum riparium and the partially humified peat below the living moss.