MIT/WHOI Joint Program in Chemical Oceanography and Marine Chemistry and Geochemistry Department, Woods Hole Oceanographic Institution Woods Hole, MA, USA.
Front Microbiol. 2011 Aug 15;2:160. doi: 10.3389/fmicb.2011.00160. eCollection 2011.
The Ross Sea is home to some of the largest phytoplankton blooms in the Southern Ocean. Primary production in this system has previously been shown to be iron limited in the summer and periodically iron and vitamin B(12) colimited. In this study, we examined trace metal limitation of biological activity in the Ross Sea in the austral spring and considered possible implications for vitamin B(12) nutrition. Bottle incubation experiments demonstrated that iron limited phytoplankton growth in the austral spring while B(12), cobalt, and zinc did not. This is the first demonstration of iron limitation in a Phaeocystis antarctica-dominated, early season Ross Sea phytoplankton community. The lack of B(12) limitation in this location is consistent with previous Ross Sea studies in the austral summer, wherein vitamin additions did not stimulate P. antarctica growth and B(12) was limiting only when bacterial abundance was low. Bottle incubation experiments and a bacterial regrowth experiment also revealed that iron addition directly enhanced bacterial growth. B(12) uptake measurements in natural water samples and in an iron fertilized bottle incubation demonstrated that bacteria serve not only as a source for vitamin B(12), but also as a significant sink, and that iron additions enhanced B(12) uptake rates in phytoplankton but not bacteria. Additionally, vitamin uptake rates did not become saturated upon the addition of up to 95 pM B(12). A rapid B(12) uptake rate was observed after 13 min, which then decreased to a slower constant uptake rate over the next 52 h. Results from this study highlight the importance of iron availability in limiting early season Ross Sea phytoplankton growth and suggest that rates of vitamin B(12) production and consumption may be impacted by iron availability.
罗斯海是南大洋中一些最大的浮游植物繁殖地之一。该系统中的初级生产力先前已显示在夏季受到铁的限制，并且周期性地受到铁和维生素 B(12) 的共同限制。在这项研究中，我们研究了罗斯海春季痕量金属对生物活性的限制，并考虑了其对维生素 B(12) 营养的可能影响。瓶培养实验表明，铁在春季限制了浮游植物的生长，而 B(12)、钴和锌则没有。这是首次在以 Phaeocystis antarctica 为主导的罗斯海春季浮游植物群落中证明铁的限制。在该位置缺乏 B(12) 的限制与先前在南大洋夏季的罗斯海研究一致，其中维生素添加并没有刺激 Phaeocystis antarctica 的生长，并且只有当细菌丰度低时，B(12) 才受到限制。瓶培养实验和细菌再生实验还表明，铁的添加直接促进了细菌的生长。在天然水样和铁施肥瓶培养中进行的 B(12) 吸收测量表明，细菌不仅是维生素 B(12) 的来源，也是一个重要的汇，并且铁的添加提高了浮游植物但不是细菌的 B(12) 吸收速率。此外，在添加高达 95 pm B(12) 时，维生素吸收速率并未达到饱和。在添加 B(12) 后 13 分钟观察到快速的 B(12) 吸收速率，然后在接下来的 52 小时内降低到较慢的恒定吸收速率。本研究的结果强调了铁供应在限制罗斯海春季浮游植物生长中的重要性，并表明维生素 B(12) 的产生和消耗速率可能受到铁供应的影响。
