Dry weight and calcium carbonate encrustation of two morphologically different Chara species: a comparative study from different lakes

Two charophyte species (Chara tomentosa Thulli. 1799 and Chara globularis L. 1753) were studied to assess their biomass and CaCO₃ production in seven hard-water lakes in Western Poland. In each lake, samples of ten individuals from three study sites were collected for dry weight (DW) and calcium carbonate content (% CaCO₃) analyses. Additionally, physicochemical parameters of water collected from the above sampling sites were analyzed.

No significant differences were found between the study sites in each lake for any of the analyzed parameters. In all the lakes, DW of C. tomentosa (0.60 ± 0.23 g indiv.^-1) was significantly higher and more differentiated than DW of C. globularis (0.11 ± 0.08 g indiv.^-1), suggesting species-specificity. The CaCO₃ content in DW for C. tomentosa was higher (58.8-70.9%) than in C. globularis (50.1-68.3%), however, it did not reflect the DW differentiation, suggesting lake-specificity. The physicochemical properties of water revealed clear lake-to-lake differentiation. Different correlations between dry weight and calcium carbonate content and lake characteristics were found for each species. The results showed that DW and % CaCO₃ are closely related to habitat conditions and different factors may influence the individual biomass of each species.