We describe seasonal changes in the biogeochemistry, microbial community and ecosystem production of two glacial snowpacks in the maritime Antarctic during a cold summer. Frequent snowfall and low, intermittent melt on the glaciers suppressed surface photosynthesis and promoted net heterotrophy. Concentrations of autotrophic cells (algae and cyanobacteria) were therefore low (average: 150–500 cells mL⁻¹), and short-term estimates of primary production were almost negligible in early summer (<0.1 μg C L⁻¹ d⁻¹). However, order of magnitude increases in Chlorophyll a concentrations occurred later, especially within the mid-snowpack and ice layers below. Short-term primary production increased to ca. 1 μg C L⁻¹ d⁻¹ in mid-summer, and reached 53.1 μg C L⁻¹ d⁻¹ in a mid-snow layer close to an active penguin colony. However, there were significantly more bacteria than autotrophs in the snow (typically 10³ cells mL⁻¹, but >10⁴ cells mL⁻¹ in basal ice near the penguin colony). The ratio of bacteria to autotrophs also increased throughout the summer, and short-term bacterial production rates (0.2–2000 μg C L⁻¹ d⁻¹) usually exceeded primary production, especially in basal ice (10–1400 μg C L⁻¹ d⁻¹). The basal ice represented the least diverse but most productive habitat, and a striking feature was its low pH (down to 3.3). Furthermore, all of the overlying snow cover became increasingly acidic as the summer season progressed, which is attributed to enhanced emissions from wet guano in the penguin colony. The study demonstrates that active microbial communities can be expected, even when snowmelt is intermittent in the Antarctic summer.

中文翻译：

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南极海洋冰川积雪生态系统微生物生产、群落组成和生物地球化学的显着季节性变化

我们描述了寒冷夏季期间南极海上两个冰川积雪的生物地球化学、微生物群落和生态系统生产的季节性变化。频繁的降雪和冰川的低位间歇性融化抑制了地表光合作用并促进了净异养。因此，自养细胞（藻类和蓝藻）的浓度很低（平均：150-500 个细胞 mL ^-1），初夏初级生产的短期估计值几乎可以忽略不计（<0.1 μg CL ^-1  d ^-1）。然而，叶绿素a浓度的数量级增加发生在较晚的时候，尤其是在积雪中部和下方的冰层内。短期初级生产增加到大约。1 μg CL ^-1 d ^-1在仲夏，并在靠近活跃企鹅群的中雪层中达到 53.1 μg CL ^-1  d ^-1。然而，雪中的细菌明显多于自养生物（通常为10 ³细胞mL ^-1，但在企鹅群附近的基底冰中>10 ⁴细胞mL ^-1）。细菌与自养生物的比例在整个夏季也有所增加，短期细菌生产率（0.2-2000 μg CL ^-1  d ^-1）通常超过初级生产，特别是在基冰中（10-1400 μg CL ^-1  d ^{-） 1}）。基底冰是多样性最少但生产力最高的栖息地，其显着特征是其低 pH 值（低至 3.3）。此外，随着夏季的进行，所有上覆的积雪都变得越来越酸，这归因于企鹅群中湿鸟粪的排放量增加。该研究表明，即使南极夏季的融雪是间歇性的，也可以预期活跃的微生物群落。