Biogeochemical cycling in fjords underpins crucial environmental and economic functions including carbon sequestration and food security, and a fundamental understanding of the controls on these cycles is essential for sustainable management of fjords that are facing increasing climate and anthropogenic stressors. However, the interaction of external forcing and local geomorphology in fjords leads to complex coupling that is challenging to measure using traditional methods, particularly in a connected coastal system like the Chiloe Inland Sea (CIS) in northern Patagonia. This study resolves key functional differences between the three major fjords (Reloncaví, Comau and Reñihue) in the CIS using high-resolution sampling of surface waters integrated with regional oceanographic and meteorological observations, models and historic data. The dominant geophysical control varied among the three fjords: river input in Reloncaví Fjord, synoptic winds in Comau Fjord and tidal forcing in Reñihue Fjord. Variable geomorphic characteristics, e.g., orientation and the location of the riverine input, resulted in contrasting physical-metabolic responses between fjords to otherwise similar meteorological and oceanic forcing conditions. Each fjord’s relative location and degree of connectivity to the CIS influenced its internal metabolic balance over synoptic to seasonal scales. In Comau Fjord, the salt fingering form of double diffusive mixing was linked to vertical density structure and wind forcing in the northern CIS; consistent trends in historical data suggest that salt fingering may be an important mechanism for delivery of nutrients to the euphotic zone. The highest metabolic rates in the study region occurred in Reñihue Fjord and were linked to vertical mixing of nutrient-rich waters to the surface in the central CIS. Climate change is predicted to result in decreasing river discharge and weakening zonal winds in northern Patagonia. Therefore, the functional relationships observed in this study imply-two key impacts of these altered forcing conditions in coming decades: 1) a lateral shift in the transfer of planktonic carbon to coastal sediments, i.e., moving landward from the CIS into fjords, and 2) greater biogeochemical variability in fjord surface waters, which will present greater management challenges for aquaculture.

峡湾中的生物地球化学循环支撑着重要的环境和经济功能，包括碳封存和粮食安全，而对这些循环的控制的基本理解对于面临日益增加的气候和人为压力源的峡湾的可持续管理至关重要。然而，外部强迫和峡湾当地地貌的相互作用导致复杂的耦合，使用传统方法难以测量，特别是在巴塔哥尼亚北部奇洛内海 (CIS) 等相连的沿海系统中。本研究通过结合区域海洋和气象观测、模型和历史数据的地表水高分辨率采样，解决了独联体三个主要峡湾（Reloncaví、Comau 和 Reñihue）之间的关键功能差异。三个峡湾的主要地球物理控制各不相同：Reloncaví 峡湾的河流输入、柯马峡湾的天气风和 Reñihue 峡湾的潮汐强迫。可变的地貌特征，例如河流输入的方向和位置，导致峡湾之间的物理代谢响应与其他相似的气象和海洋强迫条件形成鲜明对比。每个峡湾的相对位置和与独联体的连通程度影响了其内部代谢平衡，从天气到季节尺度。在柯马峡湾，双扩散混合的盐指形式与独联体北部的垂直密度结构和风力有关；历史数据的一致趋势表明，盐分可能是将营养物质输送到透光区的重要机制。研究区域的最高代谢率发生在 Reñihue Fjord，这与营养丰富的水域垂直混合到独联体中部的地表有关。预计气候变化将导致巴塔哥尼亚北部河流流量减少和纬向风减弱。因此，本研究中观察到的函数关系暗示了这些改变的强迫条件在未来几十年中的两个关键影响：1）浮游碳向沿海沉积物转移的横向移动，即从独联体向陆地移动到峡湾，以及 2 ) 峡湾地表水中更大的生物地球化学变异性，这将给水产养殖带来更大的管理挑战。预计气候变化将导致巴塔哥尼亚北部河流流量减少和纬向风减弱。因此，本研究中观察到的函数关系暗示了这些改变的强迫条件在未来几十年中的两个关键影响：1）浮游碳向沿海沉积物转移的横向移动，即从独联体向陆地移动到峡湾，以及 2 ) 峡湾地表水中更大的生物地球化学变异性，这将给水产养殖带来更大的管理挑战。预计气候变化将导致巴塔哥尼亚北部河流流量减少和纬向风减弱。因此，本研究中观察到的函数关系暗示了这些改变的强迫条件在未来几十年中的两个关键影响：1）浮游碳向沿海沉积物转移的横向移动，即从独联体向陆地移动到峡湾，以及 2 ) 峡湾地表水中更大的生物地球化学变异性，这将给水产养殖带来更大的管理挑战。