Factors that strongly affect morphological features and reproductive effort of charophytes (Charophyta, Characeae) are the depth of occurrence and light availability. Eutrophication of waters and global warming change the level and transparency of waters. As a response to light limitation, an elongation of the charophyte thallus and a decrease in the number of mature oogonia with increasing depth have been reported. The object of this study was the globally endangered charophyte Lychnothamnus barbatus, the only living representative of the genus and a sensitive bioindicator of low trophic conditions. We hypothesised that: (1) the morphological variability and (2) the number of mature oogonia decrease with increasing depth. The study was carried out in Lake Kuźnickie, a mesotrophic lake in Western Poland, hosting a stable and abundant population of L. barbatus. At shallow sites (0.5 – 4.0 m), L. barbatus revealed high variability in weight and branching of the thallus. The individuals were less elongated and produced less mature oogonia than those from deep sites (5.0 - 6.5 m). The latter were more homogeneous and characterised by significantly elongated thalli and high fertility. The first hypothesis was confirmed, while the second was falsified. We suggest that L. barbatus forms two phenotypes, one less variable and better adapted to deep waters and the other more variable and better adapted to shallow, more changeable environments. This rare macroalga may optimise resource allocation depending on environmental conditions and its phenotypic plasticity may be a key adaptation to global changes.

这强烈地影响形态特征和轮藻（生殖努力因素轮藻门，Characeae）的发生和光可用性的深度。水域的富营养化和全球变暖改变了水域的水平和透明度。作为对光限制的响应，已经报道了随着深度的增加，嗜叶藻的伸长和成熟卵的数量减少。这项研究的对象是全球濒临灭绝的自噬体Lychnothamnus barbatus，是该属的唯一活生生的代表，也是低营养条件下的敏感生物指示剂。我们假设：（1）形态变异和（2）成熟的卵的数量随深度的增加而减少。这项研究是在湖Kuźnickie，一个营养型湖泊波兰西部进行，主办稳定和丰富的人口L.石竹。在浅处（0.5 – 4.0 m），巴氏乳杆菌显示出体重和all的分支高度可变。与来自深处（5.0-6.5 m）的个体相比，个体的伸长率较小，产生的成熟卵粒也较少。后者更均质，其特征是沙眼明显延长和高生育力。第一个假设得到证实，而第二个则被证伪。我们建议巴氏乳杆菌（L. barbatus）形成两种表型，一种表型变化较小，更适合深水，另一种表型变化较大，更适合浅水，多变的环境。这种稀有的大型藻类可根据环境条件优化资源分配，其表型可塑性可能是适应全球变化的关键。