Fjords in the high Arctic, as aquatic critical zones at the interface of land-ocean continuum, are undergoing rapid changes due to glacier retreat and climate warming. Yet, little is known about the biogeochemical processes in the Arctic fjords. We measured the nutrients and the optical properties of dissolved organic matter (DOM) in both seawater and sediment pore water, along with the remote sensing data of the ocean surface, from three West Svalbard fjords. A cross-fjord comparison of fluorescence fingerprints together with downcore trends of salinity, Cl⁻, and PO₄³⁻ revealed higher impact of terrestrial inputs (fluorescence index: ~1.2–1.5 in seawaters) and glaciofluvial runoffs (salinity: ~31.4 ± 2.4 psu in pore waters) to the southern fjord of Hornsund as compared to the northern fjords of Isfjorden and Van Mijenfjorden, tallying with heavier annual runoff to the southern fjord of Hornsund. Extremely high levels of protein-like fluorescence (up to ~4.5 RU) were observed at the partially sea ice-covered fjords in summer, in line with near-ubiquity ice-edge blooms observed in the Arctic. The results reflect an ongoing or post-phytoplankton bloom, which is also supported by the higher levels of chlorophyll a fluorescence at the ocean surface, the very high apparent oxygen utilization through the water column, and the nutrient drawdown at the ocean surface. Meanwhile, a characteristic elongated fluorescence fingerprint was observed in the fjords, presumably produced by ice-edge blooms in the Arctic ecosystems. Furthermore, alkalinity and the humic-like peaks showed a general downcore accumulation trend, which implies the production of humic-like DOM via a biological pathway also in the glaciomarine sediments from the Arctic fjords.

中文翻译：

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夏季来自北极峡湾（西斯瓦尔巴特群岛）的海水和沉积物孔隙水中溶解的有机物的光谱表征

由于冰川退缩和气候变暖，北极高地的峡湾是陆地-海洋连续体交界处的水生关键区，正在经历快速变化。然而，对北极峡湾的生物地球化学过程了解甚少。我们测量了西斯瓦尔巴群岛的三个峡湾中海水和沉积物孔隙水中的养分和溶解性有机物的光学性质，以及海洋表面的遥感数据。荧光指纹与盐度的downcore趋势一起的横峡湾比较，氯^-和PO ₄ ^3-与Isfjorden和Van Mijenfjorden的北部峡湾相比，地面输入（荧光指数：海水中的〜1.2-1.5）和冰川河流径流（盐度：孔隙水中的〜31.4±2.4 psu）对霍恩松德南部峡湾的影响更大，每年向霍恩松德峡湾南部峡湾的径流增加。夏季在部分被海冰覆盖的峡湾中观察到极高水平的蛋白样荧光（至约4.5 RU），这与北极地区几乎普遍存在的冰缘开花相符。结果反映出正在进行或浮游植物开花后，叶绿素a含量较高也支持海洋表面的荧光，通过水柱的非常高的表观氧气利用率以及海洋表面的养分吸收。同时，在峡湾中观察到了特征性的伸长荧光指纹，推测是由北极生态系统中的冰缘水华产生的。此外，碱度和腐殖质样峰表现出总体的下行积聚趋势，这意味着在北极峡湾的冰川海洋沉积物中也通过生物途径产生了腐殖质样DOM。