ABSTRACT: Photophysiological and biochemical characteristics were investigated in natural communities of Arctic sea ice algae and phytoplankton to understand their respective responses towards variable irradiance and nutrient regimes. This study revealed large differences in photosynthetic efficiency and capacity between the 2 types of algal assemblages. Sea ice algal assemblages clearly displayed increased photoprotective energy dissipation under the highest daily average irradiance levels (>8 µmol photons m^-2 s^-1). In contrast, phytoplankton assemblages were generally light-limited within the same irradiance ranges. Furthermore, phytoplankton assemblages exhibited more efficient carbon assimilation rates in the low irradiance range compared to sea ice algae, possibly explaining the ability of phytoplankton to generate substantial under-ice blooms. They were also able to readily adjust and increase their carbon production to higher irradiances. The Arctic is warming more rapidly than any other oceanic region on the planet, and as a consequence, irradiance levels experienced by microalgae are expected to increase due to declining ice thickness and snow cover, as well as enhanced stratification. The results of this study suggest that sea ice algae may have less capacity to adapt to the expected environmental changes compared to phytoplankton. We therefore anticipate a change in sea ice-based vs. pelagic primary production with respect to timing and quantity in a future Arctic. The clearly distinct responses of sea ice algae vs. phytoplankton need to be incorporated into model scenarios of current and future Arctic algal blooms and considered when predicting implications for the entire ecosystem and associated biogeochemical fluxes.

中文翻译：

---

北极海冰藻的生态生理特征与浮游植物明显不同

摘要：在北极海冰藻和浮游植物的自然群落中研究了光生理和生化特性，以了解它们各自对可变辐照度和养分制度的反应。这项研究揭示了两种藻类组合在光合作用效率和容量上的巨大差异。在最高每日平均辐照度（> 8 µmol光子m ^-2 s ^-1）下，海冰藻类组合物清楚地显示出增加的光保护能量耗散）。相反，浮游植物组合通常在相同辐照度范围内受光限制。此外，与海冰藻相比，浮游植物组合在低辐照度范围内表现出更有效的碳同化率，这可能解释了浮游植物产生大量冰底花的能力。他们还能够轻松地调整碳排放并将其增加到更高的辐照度。北极的变暖速度比地球上任何其他海洋区域都要快，因此，由于冰层厚度和积雪的减少以及分层的增强，预计微藻所经历的辐照度会增加。这项研究的结果表明，与浮游植物相比，海冰藻可能缺乏适应预期环境变化的能力。因此，我们预计在未来的北极地区，海冰基础生产和远洋初级生产的时间和数量都会发生变化。需要将海冰藻与浮游植物明显不同的响应纳入当前和未来北极藻华的模型场景中，并在预测对整个生态系统和相关生物地球化学通量的影响时应加以考虑。