Ongoing sea-ice melting and associated environmental changes influence the bloom phenology and biogeochemistry of the Arctic Ocean. Kongsfjorden, a fjord in Svalbard, has already undergone the transition of being sea-ice covered in winter to sea-ice free, and now stands vulnerable to Atlantic water intrusion and glacier melting. We monitored physical and biogeochemical variables in the fjord between July 2015 and July 2016 using Indian Arctic subsurface mooring in Kongsfjorden. The year-round records of nitrate represent the first reported sensor-based observation in the region. Here, we used the high-resolution time-series of chlorophyll a, nitrate, dissolved oxygen, photosynthetically active radiation, turbidity, temperature, and salinity to study their interactions and assess how do they relate to the development of phytoplankton bloom. Results indicated a high nitrate concentration (up to 13.3 μM) and near-zero chlorophyll a in winter. The spring bloom was spotted from mid-April to the first week of June (up to 7.2 μg/L chlorophyll a at 25 m), however, with discontinuities due to high winds events. The chlorophyll a was negatively correlated with nitrate (r = −0.7, p < 0.001). Further, we observed temperature, salinity, and density characteristic of Atlantic water at 25 m and 35 m in autumn and early-winter, which coincided with nitrate peaks. This indicated nitrate supply by Atlantic inflow during the non-bloom period. We say that the features of the bloom start evolving from rather quiescent autumn and winter before it reaches an active state in spring-summer. Year-round high-resolution observations are crucial to study phytoplankton bloom phenology as any shift or change in the phenology will affect higher trophic levels and biogeochemical cycles.

持续的海冰融化和相关的环境变化影响着北冰洋的花期物候和生物地球化学。斯瓦尔巴群岛的峡湾Kongsfjorden已经经历了从冬季被海冰覆盖到无海冰的转变，并且现在容易受到大西洋水入侵和冰川融化的影响。我们在2015年7月至2016年7月期间使用Kongsfjorden的印度北极地下系泊装置监测了峡湾的物理和生物地球化学变量。全年的硝酸盐记录代表了该地区首次报告的基于传感器的观测。在这里，我们使用了叶绿素a的高分辨率时间序列，硝酸盐，溶解氧，光合有效辐射，浊度，温度和盐度，以研究它们的相互作用并评估它们与浮游植物开花的关系。结果表明，冬季硝酸盐浓度较高（高达13.3μM），叶绿素a几乎为零。从4月中旬到6月的第一个星期发现了春天的花朵（在25 m处叶绿素a高达7.2μg/ L ），但是由于强风天气而出现了不连续性。叶绿素a与硝酸盐呈负相关（r = -0.7，p <0.001）。此外，我们在秋季和初冬观察到25 m和35 m大西洋水的温度，盐度和密度特征，这与硝酸盐峰一致。这表明在非花开富贵时期，大西洋的硝酸盐供应量很大。我们说，花朵的特征从秋天到冬天的静止状态开始演变，然后在春夏季达到活跃状态。全年进行的高分辨率观测对于研究浮游植物的开花物候至关重要，因为物候的任何变化或变化都会影响较高的营养水平和生物地球化学循环。