## 1 Introduction  
Macrophyytes play an important role in assessing the condition of aquatic ecosystems [1, 2, 3]. Indeed, in European countries, various macrophyte indices are often used to determine surface water quality: the Macrophyte Index (lake), Trophic Index of Macrophytes (river), the Mean Trophic Rank (river), Indice biologique macrophytique en riviere (river), the Ecological State Macrophyte Index (lake), and the Macrophyte River Index (river) [4]. One particularly well-known pleustophyte species whose presence in water is known to influence these indicators is _Hydrocharis morsus-ranae_, or frogbit [5, 6]. _Hydrocharis morsus-ranae_ ranges from Europe to Northern Asia [7, 8]. The plant inhabits stagnant eutrophic and mesotrophic waters and is most often present in communities with _Stratiotes aloides_ (_Hydrocharitetum morsus-ranae_ [PERSON] 1935) and _Lemma minor_ (Lemno minors-_Hydrocharitetum morsus-ranae_ [PERSON] 1978) [9, 10]. It is believed to play an important role in maintaining the biodiversity of aquatic biotopes [11, 12]. However, it continues to spread in North America and India, where it is treated as an invasive plant, despite numerous attempts to limit its presence [13, 14, 15, 16, 17]. Its expansion has also been noticed in Poland and Romania [18, 19]. Various studies indicate that the species demonstrates considerable adaptability to changing environmental conditions and high resistance to habitat pollution with heavy metals (HMs) [20; 21; 22; 23; 24; 25]. Elevated HM levels are often observed in river and lake catchments as a result of anthropopressure [26; 27], particularly that associated with industry, agriculture, and road transport [28]. Heavy metals are highly persistent and non-degradable, and tend to bioaccumulate, making them difficult to remove. One of the most toxic heavy metals is cadmium [29]. It is an active non-redox element without any known biological function and is toxic to aquatic plants [30]. The ability of plants to accumulate metals in their mass makes it possible to use them for the purpose of purification of a contaminated environment [31]. Conventional methods of removing HMs from aquatic ecosystems, such as chemical precipitation, microfiltration, adsorption, or ion exchange, are very expensive and technologically difficult to apply and also have a negative impact on aquatic organisms [32; 33]. Therefore, phytoremediation, which is an alternative and environmentally friendly method, is of great interest to researchers. This method, like any other, has its opportunities, but also its limitations [22; 23]. Aquatic plants whose phytoremediation functions are best known include: _Phragmites australis, Typha latifolia, Potamogeton pectinuts, Ceratophyllum denersum, Myriophyllum spicatum_, and _Eichlornia crassipes_ or _Lenna minor_[34; 35; 36]. Depending on the three major growth forms of aquatic plants (free-floating, sediment rooted with emerged, and/or floating leaves and submerged), various phytoremediation techniques (phytoextraction, rhizoflitration, phytostablization, phytotransformation/phytodegradation) play a greater or lesser role in the effective removal HMs from the aquatic ecosystem [33; 37]. One of the most effective phytoremediation technologies is phytoextraction, especially when we use HMs hyperaccumulators that have the ability to accumulate metals in water bodies in a very high concentration, without the phytotoxic effect [38]. Little is known of frogbit, apart from its distribution and physicochemical environment, although in some studies have assessed its phytoremediation potential regarding some metals. As such, there is a need to determine its growth potential in environments contaminated with cadmium under the influence of various biogenic compounds [39; 40; 41; 42].