海底地下水排放对典型红树林蓝碳收支的影响——以广西珍珠湾为例

Influence of submarine groundwater discharge in the blue carbon budget of typical mangrove:A case study from the Zhenzhu Bay,Guangxi

海底地下水排放(Submarine Groundwater Discharge,SGD)是陆海相互作用的重要表现形式之一,其携带的物质对近岸海域生源要素的收支有重要影响。本文利用222Rn示踪技术估算了我国典型红树林海湾—广西珍珠湾在2019年枯季(1月)SGD携带的碳通量。调查发现,地下水中222Rn活度、溶解无机碳(DIC)和溶解有机碳(DOC)的平均浓度均高于河水和湾内表层海水。利用222Rn质量平衡模型估算得到珍珠湾SGD速率为(0.36±0.36)m/d,SGD输入到珍珠湾的DIC和DOC通量分别为(2.41±2.63)×10^7 mol/d和(1.96±2.20)×10^6 mol/d。珍珠湾溶解碳的源汇收支表明,SGD携带的DIC和DOC分别占珍珠湾总DIC和总DOC来源的91%和89%。因此,SGD携带的DIC和DOC是珍珠湾DIC和DOC的主要来源,是海岸带蓝碳收支和生物地球化学循环过程中的重要组成。

As one of the forms of land-ocean interactions,submarine groundwater discharge(SGD)can release solutes into the coastal sea and has a significant impact on the nutrients budget in coastal seawater.Here,using 222Rn tracer,the SGD and the associated dissolved inorganic carbon(DIC)and dissolved organic carbon(DOC)inputted to the Zhenzhu Bay,a typical mangrove-dominated bay,were quantified.The results show that the average concentrations of 222Rn,DIC and DOC in groundwater are relatively higher than those in river water and surface sea water.A 222Rn mass balance implies that SGD rate is(0.36±0.36)m/d during January 2019.And SGD-derived DIC and DOC fluxes are estimated to be(2.41±2.63)×10^7 mol/d and(1.96±2.20)×10^6 mol/d.It confirmed that SGD-derived carbon is the most important carbon source in this bay,with 91%DIC and 89%DOC of the total input fluxes by SGD,respectively.Our results highlight the importance of groundwater-derived carbon fluxes in the Zhenzhu Bay,especially in the blue carbon assessments and biogeochemical process in tidal zones such as mangrove ecosystems.