基于自主水下滑翔机观测的马尾藻海中部年净群落生产力与碳输出
Annual net community production and carbon exports in the central Sargasso Sea from autonomous underwater glider observations
AI总结：
针对BATS站点船基采样尺度不足导致年净群落生产力与碳输出估算不匹配的问题，本研究用搭载生物地球化学传感器的自主水下滑翔机开展全年观测，提升了估算一致性并揭示了相关碳循环机制。
摘要：
尽管已在百慕大大西洋时间序列研究（BATS）站点开展了数十年船基观测，我们对该区域年度碳循环的认知仍存在模糊之处。年净群落生产力（ANCP）的地球化学估算值与营养盐输送、碳输出（EP）的直接测量结果难以匹配，这意味着要么我们对这些过程的理解存在不足，要么这些过程发生的时间和空间尺度小于月度采样所能解析的范围。我们针对后者的问题，使用搭载生物地球化学传感器的自主水下滑翔机，基于完整年度周期内氧气（O₂）和硝酸盐（NO₃）的质量平衡来量化ANCP。O₂产生、消耗的时间、幅度与分布，以及NO₃通量，再次印证了物理强迫和营养结构的强季节性会形成双重系统：上半年真光层的生产力由深层供应的NO₃支撑，下半年则由上层海洋内部的营养盐循环维持。研究证据还支持近期提出的关于具有非Redfield特征（氮、磷匮乏）的碳生产与循环的假说，该假说可解释在无显著NO₃供应情况下观测到的高净群落生产力（NCP）模式。研究还发现，春季所有对流活动停止后，垂直迁移的樽海鞘群落可能对ANCP和EP有显著贡献。数据集分辨率的提升，结合对真光层和亚真光层积分深度更精准的定义，使得ANCP和EP的估算值彼此更为吻合。
英文摘要：
Despite decades of ship-based observations at the Bermuda Atlantic Timeseries Study (BATS) site, ambiguities linger in our understanding of the region's annual carbon cycle. Difficulties reconciling geochemical estimates of annual net community production (ANCP) with direct measurements of nutrient delivery and carbon exports (EP) have implied either an insufficient understanding of these processes, and/or that they are playing out on shorter time and spatial scales than resolved by monthly sampling. We address the latter concern using autonomous underwater gliders equipped with biogeochemical sensors to quantify ANCP from mass balances of oxygen (O2) and nitrate (NO3) over a full annual cycle. The timing, amplitude and distribution of O2 production, consumption, and NO3 fluxes reaffirm ideas about strong seasonality in physical forcing and trophic structure creating a dual system: i.e. production fueled by NO3 supplied to the photic zone from deeper layers in the first half of the year, versus being recycled within the upper ocean during the second half. The evidence also supports recently proposed hypotheses regarding the production and recycling of carbon with non-Redfield characteristics, deplete in nitrogen and phosphorus, to explain observed patterns of high NCP in the absence of significant NO3 supply. It further identifies significant contributions to ANCP and EP potentially linked to vertically migrating communities of salps in spring after all convective activity has ceased. The improved resolution of the datasets, combined with more precise definitions of photic and subphotic integration depths, brings the estimates of ANCP and EP into better alignment with each other.
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