Spatiotemporal variations in water dissolved organic carbon and dissolved inorganic carbon concentrations in Wenwusha Reservoir in subtropical estuary, Southeast China

Abstract

沿海水库汇聚并埋藏着大量的碳，是全球碳循环的重要区域.水体溶解有机碳（DOC）和溶解无机碳（DIC）的生物地球化学行为是水库碳循环研究的重要组成部分，对其系统生物过程和生态环境变化具有重要的影响.为了解亚热带河口区文武砂水库表层水体DOC和DIC的时空分布特征，本研究于2018年11月、2019年3月和6月分别对库区表层水进行多空间点位采样分析.结果表明，研究期间，文武砂水库表层水体DOC和DIC浓度变化范围分别介于0.10～21.13和0.38～34.94 mg/L，其均值分别为（4.09±0.18）和（15.83±0.24） mg/L，最大值分别出现在夏季和秋季；空间分布趋势，整体表现为北库区>南库区，且由库区周边的浅水区向库区中心的深水区域呈现出递减的趋势；浮游植物光合作用强度是影响库区DOC和DIC浓度的季节变化的重要因素，而外源污染输入强度是引起库区DOC和DIC浓度空间变化的重要因素.本文结果扩展对水库碳循环的认知，对提高水库水质也提供了有益参考.;Coastal reservoirs receive and accumulate a large amount of carbon; therefore, they are important areas for global carbon cycling. The biogeochemical cycles of dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) are important components of coastal reservior carbon cycle, with significant effects on biological process and environmental change. This study was conducted to analyze the spatiotemporal variation in DOC and DIC concentrations at Wenwusha Reservoir, a subtropical coastal reservoir in Southeast China, based on the high spatial resolution filed sampling in November 2018 (autumn), March 2019 (spring), and June 2019 (summer). The results showed that the DOC and DIC concentrations of the surface water in Wenwusha Reservoir during the research period changed in the ranges of 0.10-21.13 mg/L, 0.38-34.94 mg/L, with mean values of 4.09±0.18 mg/L and 15.83±0.24 mg/L, respectively. Temporally, concentrations of DOC and DIC in the reservoir showed the highest values in summer and autumn, respectively. Spatially, DOC and DIC concentrations in the northern part of the reservoir were higher than those in the southern part. Furthermore, the DOC and DIC concentrations decreased along a gradient from shallow water (<1 m) to deeper water (>3 m) in the reservoir. The seasonal variations in DOC and DIC concentrations were mainly influenced by phytoplankton photosynthesis, while the spatial changes of DOC and DIC concentrations were primarily affected by exogenous input (e.g., sewage discharge and river flow). The results improve the understanding of carbon cycling in aquatic ecosystem and also be helpful for improving water quality in reservoirs.