Highly saline conditions represent a strong challenge for most microorganisms in freshwater ecosystems. Eukaryotic freshwater green algae from the Chlorophyta clade were investigated for their ability to survive in and adapt to increased salt concentration in the growth medium. Striking differences were detected between the responses of the various algae species to the elevated salt concentrations. The investigated Chlamydomonas reinhardtii cc124 and Coelastrella sp. MACC-549 algae showed a moderate resistance to increased salt concentration, while Chlorella sp. MACC-360 exhibited high salt tolerance, showed unaltered growth characteristics and photosynthetic efficiency compared to the saline-free control conditions even at 600 mM NaCl concentration. Diverse physiological responses to elevated salt concentrations were described for the tested algae including variations in their growth capacity, characteristic morphological changes, alterations in the structure and function of the photosynthetic machinery and differences in the production of reactive oxygen species. Special alterations were identified in the lipid and exopolysaccharide production patterns of the tested algal strains in response to high salinity. As a conclusion Chlorella sp. MACC-360 algae showed outstanding salt tolerance features. Together with the concomitant lipid-producing phenotype under highly saline conditions this unicellular green alga is a promising candidate for biotechnological applications.

This study investigated the effects of elevated copper levels on the early-stage growth and development of three Arundo donax (giant reed) ecotypes (STM, BL, and ESP) from different climatic zones, focusing on plant morpho-physiological and copper biochemical changes (including root structure, photosynthetic structure, copper accumulation and translocation, soluble protein, and lipid peroxidation). Plants were grown under increasing concentrations of copper (0, 100, 200, 300, and 400 mg/kg), revealing that copper accumulation was predominantly localized in the roots, with ESP showing the highest at 1829 μg/g, followed by STM (1191 μg/g) and BL (935 μg/g) at 400 mg/kg. While morphological traits like plant height and stem diameter were less affected, root volume decreased significantly at high copper levels (e.g., by 60 % in BL from 10.00 cm³ in control to 4.00 cm³ at 400 mg/kg). Physiological responses varied significantly: photosynthetic pigments increased with moderate copper levels (e.g., chlorophyll a in BL from 31.67 μg/cm² in control to 49.19 μg/cm² at 400 mg/kg) but declined at higher concentrations in ESP. Lipid peroxidation, measured by malondialdehyde (MDA), indicated increased oxidative stress, especially in STM and ESP (e.g., root MDA in STM from 14.22 nmol/g in control to 26.30 nmol/g at 400 mg/kg). These results highlight the ESP ecotype's higher tolerance and copper sequestration capabilities, making it a promising candidate for further studies in copper-stressed environments.