在各种营养条件下,蓝藻在湖泊中占主导地位。其中,两种有害的丝状蓝细菌,即浮游生物agardhii和松香,占据完全不同的生态位,在那里他们可以形成密集的种群。在本研究中,我们研究了环境条件对这些物种在不同营养状态的湖泊中的生长和垂直分布的影响。此外,我们强调了根据欧盟水框架指令评估湖泊生态状况的某些不便之处。在0.5-1m深度的富营养化湖泊中记录了最高的P.agardhii生物量,在高光强度下。同时,冬凌草的生物量最高,记录了深层叶绿素最大值,在11-12米深度的中营养湖泊中观察到,通常在非常低的光强度下的共生区以下。冬凌草,但不是P.agardhii,对浮游植物的多样性和生物量产生了强烈的化感作用。此外,这两个物种都利用不同的溶解氮组分进行生长;特别是,P.agardhii使用铵态氮,而冬凌草使用硝酸盐氮。此外,溶解的磷对冬凌草的生长产生了潜在的限制作用。总的来说,经过测试的波兰PMPL,德国PSI,和爱沙尼亚浮游植物指数确实有助于评估湖泊的生态状况,尽管仅限于蓝细菌生物量高的富营养化湖泊(P.agardhii)在上层水层中。然而,在对蓝藻生物量高的湖泊进行适当评估时出现了问题(P.冬凌草)的叶绿素最大值在富营养区的范围之外。在这种情况下,两个测试指数,即波兰和德国指数,允许从富光层中收集样品,这显著影响了计算中包含的样本数量。因此,湖泊生态状况的正确计算是不确定的。只有爱沙尼亚指数允许从两到三层热水中收集样本,包括冬凌草的开花层。因此,爱沙尼亚指数提供了最适合计算的指标。
Cyanobacteria dominate lakes under diverse trophic conditions. Of these, two harmful filamentous cyanobacterial species, namely Planktothrix agardhii and P. rubescens, occupy completely different ecological niches in which they can form dense populations. In the present study, we investigated the effects of environmental conditions on the growth and vertical distribution of these species in lakes of different trophic statuses. Moreover, we underscored certain inconveniences in the assessment of the ecological status of lakes according to the European Union Water Framework Directive. The highest biomass of P. agardhii was recorded in eutrophic lake at a depth of 0.5-1 m, under high light intensity. Meanwhile, the highest biomass of P. rubescens, at which the deep chlorophyll maximum was recorded, was observed in mesotrophic lakes at a depth of 11-12 m, often below the euphotic zone under very low light intensity. P. rubescens, but not P. agardhii, exerted a strong allelopathic effect on the diversity and biomass of phytoplankton. Moreover, both species utilised different dissolved nitrogen fractions for their growth; specifically, P. agardhii used ammonium nitrogen, whilst P. rubescens used nitrate nitrogen. Furthermore, dissolved phosphorus produced a potentially limiting effect on P. rubescens growth. Overall, the tested Polish PMPL, German PSI, and Estonian phytoplankton indices were indeed useful in the assessment of the ecological status of lakes, albeit limited to the eutrophic lake with a high biomass of cyanobacteria (P. agardhii) in the upper water layers. However, problems arose in the proper assessment of lakes with a high biomass of cyanobacteria (P. rubescens) with a deep chlorophyll maximum outside the range of the euphotic zone. In such cases, two of the tested indices, namely the Polish and German indices, allowed sample collection from the euphotic layers, which significantly affected the number of samples included in the calculation. Consequently, the correct calculation of the ecological status of the lake was uncertain. Only the Estonian index allowed for a sample collection from two to three thermal layers of water, including the bloom layer of P. rubescens. Hence, the Estonian index offered the best fit for calculations.