Abstract Microalgal cells collected with moored sediment traps deployed during three to five annual cycles at three sites in the Beaufort Sea were identified to investigate variations in the timing, abundance and composition of microalgal fluxes in relation to snow and sea ice cover. The investigation period encompassed two extremes in snow and sea ice conditions: a delayed melt due to an ice rebound in 2013 and a premature snowmelt and sea ice breakup that led to an ice-free Beaufort Sea in 2016. Diatoms dominated the microalgal fluxes, with the pelagic centric diatoms Thalassiosira spp. and the ice-associated pennate diatoms Fragilariopsis spp. consistently collected at the three sites. The export of the ice-obligated algae Nitzschia frigida indicated the release of sea ice algae at the onset of snowmelt. Early snowmelt and sea ice breakup in 2016 contributed to an early start of ice algae release accompanied with early peaks in diatom fluxes and higher diatom and phytoplankton carbon (PPC) fluxes during spring and summer. Conversely, delayed sea ice algae release, low diatom fluxes, and low PPC fluxes were observed when snowmelt and sea ice breakup occurred late over the Mackenzie shelf break. The amount of diatoms exported at ∼100 to 300 m also likely depended on a match or mismatch between algal production and zooplankton grazing. Variations in the snow and sea ice regimes at the regional scale therefore directly impact the timing and magnitude of microalgal export and its contribution to particulate organic carbon flux in the Arctic Ocean. With global warming, the ongoing sea ice reduction in the Arctic Ocean may increase PPC fluxes to the seafloor and potential carbon sequestration at depth.

中文翻译：

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早期融雪和海冰破裂促进了波弗特海的藻类出口

摘要 确定了在波弗特海三个地点的三到五个年度周期中部署的系泊沉积物陷阱收集的微藻细胞，以研究与雪和海冰覆盖相关的微藻通量的时间、丰度和组成的变化。调查期间包括雪和海冰条件的两个极端：2013 年冰反弹导致的延迟融化和 2016 年导致波弗特海无冰的融雪和海冰过早破裂。硅藻主导了微藻通量，与远洋中心硅藻 Thalassiosira spp。和与冰有关的羽状硅藻 Fragilariopsis spp。在三个地点持续收集。冰藻 Nitzschia frigida 的出口表明在融雪开始时海冰藻的释放。2016 年的早期融雪和海冰破裂导致冰藻释放的早期开始，伴随着硅藻通量的早期峰值以及春季和夏季更高的硅藻和浮游植物碳（PPC）通量。相反，当融雪和海冰破裂在 Mackenzie 大陆架断裂处发生较晚时，观察到延迟的海冰藻释放、低硅藻通量和低 PPC 通量。在 100 至 300 m 处出口的硅藻数量也可能取决于藻类生产和浮游动物放牧之间的匹配或不匹配。因此，区域尺度上雪和海冰状况的变化直接影响微藻出口的时间和数量及其对北冰洋颗粒有机碳通量的贡献。随着全球变暖，