Significance of HCO3- alkalinity in calcification and utilization of dissolved inorganic carbon in Chara vulgaris

Abstract

To investigate the influence of HCO 3 − alkalinity on calcification in thalli of the genus Chara, we studied the effects of increased light level and additional HCO 3 − on calcification rate in C. vulgaris at various hours (30 min, 8 h, 12 h, 12.5 h, 20 h and 24 h after treatment) in a 24 h experiment (12 h light:12 h dark). We identified a significant Pearson's correlation between exogenous dissolved inorganic carbon (DIC) concentrations and the utilization of DIC (µmol C g −1 fresh weight). Plotting the daily rhythm of DIC utilization produced negative quadratic curves. Furthermore, calcification rate (µmol Ca h −1 g −1) was linearly related to DIC utilization rate (DIC uptake ; µmol C h −1 g −1 ), indicating that the calcification rate is dependent on DIC uptake . However, ratios of calcification to the utilization of DIC were decreased at high light intensity and increased with HCO 3 − addition, which was mainly ascribed to changes in the ratio of calcification to photosynthesis. Chlorophyll fluorescence results provided direct evidence for the promotion of photosynthesis in Chara thalli by both high light and DIC addition and their positive influence on maximum relative electron transport rate. These results suggest that calcification in calcareous C. vulgaris is mainly restrained by HCO 3 − alkalinity, which could explain the correlation between calcification of Chara thalli and alkalinity of water bodies in the field.

Interspecific Differences in the Effects of Calcium and Phosphorus Coprecipitation Induced by Submerged Plants on the Water-to-Phosphorus Cycle

“…According to [17], coprecipitation is widely regarded as a significant method for lake water purification. The precipitation of CaCO 3 in lakes and the formation of autogenic precipitates of extracellular CaCO 3 are caused primarily by the microenvironment created by the photosynthesis of submerged organisms or by an excess of Ca 2+ in local water bodies [18,19]. For example, when CaCO 3 is supersaturated in water (SI > 1), an increase in the P content in the water lead to a fourfold increase in the inorganic phosphorus content in the ash phosphorus of Chara vulgaris and more than 60% of the ash phosphorus precipitated into calcium carbonate phosphorus [20].…”