## 2 Materials and Methods
### Field and Laboratory Works  
The microphytobenthos used in the laboratory study was collected from slides exposed in the coastal zone of the southern Baltic Sea (Gulf of Gdarsk) at a station located at 54\({}^{\circ}\)26\({}^{\circ}\)49\({}^{\prime\prime}\) N, 8\({}^{\circ}\)34\({}^{\circ}\)24\({}^{\prime\prime}\) E for a period of 14 days in summer (August) 2015. The methodology of the field work is presented in detail in [PERSON] et al. [57]. After transporting the panels to the laboratory, the material was prepared for further testing. After sonification and nitrogen desaturation to remove animal organisms, microphytobenthos cells of 44,273 (\(\pm\)2151) in 1 mL were placed in 250 mL flasks in 100 mL of seawater collected in situ. The measured concentrations of biogenic compounds in seawater were: N-NH\({}_{4}\) 9.4 mg\(\cdot\)m\({}^{-3}\), N-NO\({}_{3}\) 102 mg\(\cdot\)m\({}^{-3}\), P-PO\({}_{4}\) 36 mg\(\cdot\)m\({}^{-3}\), Si-SiO\({}_{4}\) 600 mg\(\cdot\)m\({}^{-3}\). Based on preliminary tests, it was shown that such concentrations of biogenic salts do not limit the growth of microalgae [57]. Light conditions with a PAR irradiance of 60 umol photons m\({}^{-2}\) s\({}^{-1}\) and an L:D photoperiod of 16:8 were obtained using an artificial light source: Phillips halogen lamps (OSRAM L 36W/640-1). In the tests, copper (II) chloride, glyphosate, and the ionic liquid BMIM[Cl] were used to compare effects of substances from different chemical groups with distinct mechanisms of action on living organisms and varying levels of toxicity on natural microphytobenthic communities. The concentration values of the test substances were selected on the basis of maximum acceptable concentrations of selected compounds in the environment introduced by legislation [58] and the literature [37; 59] as well as on the basis of previous studies of our own [55]. The following concentrations were used in the ecotoxicological tests: for copper (II) chloride, 2\(\cdot\)10\({}^{-5}\) g\(\cdot\)dm\({}^{3}\) and 2\(\cdot\)10\({}^{-3}\) g\(\cdot\)dm\({}^{-3}\); for glyphosate, 4.2\(\cdot\)10\({}^{-2}\) g\(\cdot\)dm\({}^{-3}\), 8.5\(\cdot\)10\({}^{-1}\) g\(\cdot\)dm\({}^{-3}\), and 8.5 g\(\cdot\)dm\({}^{-3}\); and for ionic liquid [BMIMC]], 1.13\(\cdot\)10\({}^{-3}\) g\(\cdot\)dm\({}^{-3}\) and 1.75\(\cdot\)10\({}^{-2}\) g\(\cdot\)dm\({}^{-3}\). All variants of the experiment were carried out in 3 replicates. The values used were high but were intended to reflect a sudden one-off influx of high concentrations of test substances into the environment. Undertaking the study, it was assumed that the microhypotethnic communities extracted from the environment had not adapted to the elevated values of the compounds tested. For example, the content of copper ions in the area of their cultivation is at the level of 1.3\(\cdot\)10\({}^{-7}\)-1.1\(\cdot\)10\({}^{-6}\) g\(\cdot\)dm\({}^{-3}\)[60]. In turn, [PERSON] et al. [59] showed that in river mouths in the Baltic Sea, concentrations of glyphosate range from 2.8\(\cdot\)10\({}^{-8}\) g\(\cdot\)dm\({}^{-3}\) to 1.68\(\cdot\)10\({}^{-6}\) g\(\cdot\)dm\({}^{-3}\), while APMA is detected in all of them. In studies conducted in rivers in Germany, 1310 different ionic liquid pollutants were identified, but only ca. 20 compounds were detected in concentrations of up to ug\(\cdot\)dm\({}^{-3}\)[61]. Observations of changes in the composition and structure of microhypotethnic communities were carried out using the principles adopted in the OECD Guidelines for the Assessment of the Effects of Chemical Toxicity on Plant Microorganisms [62]. The microalgae were identified using various taxonomic keys and floras [63; 64; 65; 66; 67; 68; 69; 70]. Qualitative and quantitative analysis of communities was conducted using a Nikon (Japan) 80i microscope equipped with a DS-U2 camera at \(\times\)400 magnification. In addition, changes in the shape of chloroplasts of microhypotethnic cells were analysed according to a previously developed research methodology [9; 55].