title: The mitigating effect of calcification-dependent of utilization of inorganic carbon of Chara vulgaris Linn on NH4-N toxicity.
abstract: Increased ammonium (NH4-N) concentrations in water bodies have been reported to adversely affect the dominant species of submersed vegetation in meso-eutrophic waters worldwide. However calcareous plants were lowly sensitive to NH4-N toxicity. In order to make clear the function of calcification in the tolerance of calcareous plants to NH4-N stress, we studied the effects of increased HCO3(-) and additional NH4-N on calcification and utilization of dissolve inorganic carbon (DIC) in Chara vulgaris Linn in a 7-d sub-acute experiment (light:dark 12:12h) carried out in an open experimental system in lab. Results revealed that calcification was dependent of utilization of dissolve inorganic carbon. Additional HCO3(-) significantly decreased the increase of pH while additional NH4-N did not. And additional HCO3(-) significantly improved calcification while NH4-N did in versus in relation to the variation of DIC concentration. However, addition of both HCO3(-) and NH4-N increased utilization of DIC. This resulted in calcification to utilization of DIC ratio decreased under additional NH4-N condition while increased under additional HCO3(-) conditions in response to the variation of solution pH. In the present study, external HCO3(-) decreased the increase of solution pH by increasing calcification, which correspondingly mitigated the toxic effect of high NH4-N. And we argue that the mitigating effect of increased HCO3(-) on NH4-N toxicity is dependent of plant calcification, and it is a positive feedback mechanism, potentially leading to the dominance of calcareous plants in meso-eutrophic water bodies.
authors.affiliation: Donghu Experimental Station of Lake Ecosystems, State Key Laboratory for Freshwater Ecology and Biotechnology of China, Institute of Hydrobiology, The Chinese Academy of Sciences, Donghu South Road 7, Wuhan 430072, People's Republic of China.
authors.forename: Heyun
authors.initials: H
authors.lastname: Wang
authors.forename: Leyi
authors.initials: L
authors.lastname: Ni
authors.forename: Ping
authors.initials: P
authors.lastname: Xie
mesh_terms: D064751:Ammonium Compounds / Q000633:toxicity*; D001639:Bicarbonates / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002244:Carbon / Q000378:metabolism*; D044784:Chara / Q000187:drug effects* / Q000378:metabolism* / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D013312:Stress, Physiological / Q000187:drug effects
chemical_list: D064751:Ammonium Compounds; D001639:Bicarbonates; D002244:Carbon; D002118:Calcium
keywords: Ammonium; Calcification; Dissolve inorganic carbon utilization; Meso-eutrophic water