36 research outputs found
Physiological comparison of copper toxicity in the lichens Peltigera rufescens (Weis) Humb. and Cladina arbuscula subsp. mitis (Sandst.) Ruoss
Spatial and temporal variation in microcystin concentrations during perennial bloom of Planktothrix agardhii in a hypertrophic lake
Temporal and spatial variation in the concentrations of intra- and extra-cellular microcystins were studied in a hypertrophic
lake with bloom of Planktothrix agardhii (Gomont) Anagnostidis et Komarek. Concomitantly with increase in water
temperature (from 2 to 20 °C) abundance of P. agardhii increased from 1.9 x 105 to 4.3 x 107 trichomes L-1. In autumn, in spite
of temperature lower (14°C) than in summer it was still very high. Mass development of P. agardhii (to 6 x 106 L-1 and higher)
caused a severe decrease in water transparency (to 0.5 - 0.2 m in summer/autumn). The cyanobacterium density was relatively
uniform within water column; only in summer (July) it was significantly higher (by about 30%) in surface than in bottom layer.
From spring to autumn microcystins (MCs) were mainly biomass-bound (up to 90 μg MC-LR equiv. L-1), whereas the level of
extra-cellular toxins was much lower (up to 2 μg L-1) and relatively stable. Only in winter, high amounts of MCs (11.3 μg L-1)
were released from decaying biomass into water. The increasing concentrations of biomass-bound microcystins in the lake water
positively correlated (R2 = 0.9863; y = -0.1285x2 + 7.14x ) with the abundance of P. agardhii and the highest concentrations of
the intracellular MC fraction were found during the exponential phase of P. agardhii growth. In addition, the surface-sampled
biomass of P. agardhii contained in autumn 2-fold more MCs (2.75 μg MC-LR equiv. per 106 P. agardhii trichomes) than the
bottom-sampled one (1.41 μg MC-LR equiv. per 106 trichomes). This is the first report showing that despite the homogenous
distribution of P. agardhii in water column of a shallow lake, various seasonal and spatial distributions of both extra-cellular
and intracellular fractions of microcystins occur