The carbonate chemistry was investigated in the semiarid eutrophic Araruama Lagoon (Brazil), one of the largest hypersaline coastal lagoons in the world. Spatial surveys during winter and summer periods were performed, in addition to a diurnal sampling in summer. The hypersaline waters have higher concentrations of total alkalinity (TA) and dissolved inorganic carbon (DIC) than the seawater that feed the lagoon, due to evaporation. However, TA and DIC concentrations were lower than those expected from evaporation. Calcium carbonate (CaCO₃) precipitation partially explained these deficits. The negative correlation between the partial pressure of CO₂ (pCO₂) and chlorophyll a (Chl a) indicated that DIC was also consumed by primary producers. The uptake by photosynthesis contributes to 57–63% of DIC deviation from evaporation, the remaining credited to CaCO₃ precipitation. Marked pCO₂ undersaturation was prevalent at the innermost region with shallow, confined, and phytoplankton-dominated waters, with a strong enrichment of heavier carbon isotope (δ¹³C-DIC up to 5.55‰), and highest pH (locally counter-acting the process of ocean acidification). Oversaturation was restricted to an urbanized region, and during night-time. The lagoon behaved as a marked CO₂ sink during winter (− 15.32 to − 10.15 mmolC m⁻² day⁻¹), a moderate sink during summer (− 5.50 to − 4.67 mmolC m⁻² day⁻¹), with a net community production (NCP) of 93.7 mmolC m⁻² day⁻¹ and prevalence of net autotrophic metabolism. A decoupling between CO₂ and O₂ exchange rate at the air–water interface was attributed to differences in gas solubility, and high buffering capacity. The carbonate chemistry reveals simultaneous and antagonistic actions of CaCO₃ precipitation and autotrophic metabolism on CO₂ fluxes, and could reflect future conditions in populated and semiarid coastal ecosystems worldwide.

在半干旱的富营养化阿拉鲁阿玛泻湖（巴西）中研究了碳酸盐化学，该泻湖是世界上最大的高盐度沿海泻湖之一。除了夏季的昼夜抽样外，还进行了冬季和夏季的空间调查。由于蒸发，超咸水的总碱度 (TA) 和溶解的无机碳 (DIC) 浓度高于为泻湖提供营养的海水。然而，TA 和 DIC 浓度低于蒸发预期的浓度。碳酸钙 (CaCO ₃ ) 沉淀部分解释了这些缺陷。CO ₂分压（p CO ₂）与叶绿素a（Chl a）负相关) 表明 DIC 也被初级生产者消费。光合作用的吸收贡献了 57-63% 的 DIC 蒸发偏差，其余的归功于 CaCO ₃沉淀。显着的p CO ₂欠饱和现象普遍存在于浅层、密闭和浮游植物为主的水域的最内层，重碳同位素（δ ¹³ C-DIC 高达 5.55‰）的富集程度很高，pH 值最高（局部反作用）海洋酸化过程）。过饱和仅限于城市化地区和夜间。泻湖在冬季表现为显着的 CO ₂汇（− 15.32 至 − 10.15 mmolC m ^-2天^-1)，夏季适度下沉（- 5.50 至- 4.67 mmolC m ^-2天^-1），净群落产量（NCP）为 93.7 mmolC m ^-2天^-1和净自养代谢的流行。空气-水界面处 CO ₂和 O ₂交换率之间的脱钩归因于气体溶解度的差异和高缓冲能力。碳酸盐化学揭示了 CaCO ₃沉淀和自养代谢对 CO ₂通量的同步和拮抗作用，可以反映全球人口稠密和半干旱沿海生态系统的未来状况。