Collaborative Research: Iron and Light Effects on Phaeocystis Antarctica Isolates from the Ross Sea

南极棕囊藻是南极大陆架水域中一种主要的水华形成藻类，与硅藻一样，被认为是影响区域生物地球化学循环和生态系统结构的关键物种。在仲夏到夏末，这些水域中的铁含量下降到低至约0.1海里，这一浓度可能会限制浮游植物的生长，包括南极洲的浮游植物。然而，与硅藻相比，很少有人研究铁的影响，也就是铁和辐射的组合对南极洲冰藻的生长、生理和生化组成的影响。本项目将从南罗斯海采集南极洲细菌，并在查尔斯顿大学进行半连续分批培养，以研究铁的有效性和光照对南极洲冰藻生长速度、细胞铁配额、浮力、生物硫生产、色素含量、氧化还原蛋白表达和光合作用效率的影响。众所周知，南极洲棕囊藻对罗斯海的碳、营养元素和硫的区域生物地球化学循环有重大影响，时间尺度从季节性到年际不等。该物种还可能在推断的与冰期-间冰期气候变化有关的生物地球化学循环的盆地规模变化中发挥核心作用。因此，必须从机械上了解控制南极假单胞菌生长、生理和生化组成的因素，以便更好地了解罗斯海和更广泛的南大洋的生物地球化学生态，以及与区域和全球气候的可能联系。加上最近和正在进行的实地和模拟研究的结果，这些实验室实验提供的信息将极大地提高我们预测南极地区将如何受到未来气候变化的影响和调节的能力。

The colonial prymnesiophyte Phaeocystis antarctica is a major bloom-forming alga in Antarctic shelf waters; where, alongside diatoms, it is considered a keystone species in its impact on regional biogeochemical cycling and ecosystem structure. Iron levels in these waters fall to values as low as ~0.1 nM during the mid to late summer, concentrations that are likely to limit the growth of phytoplankton, including P. antarctica. However, in contrast to diatoms, very little work has been conducted to examined the effects of iron, or the combined effects of iron and irradiance, on the growth, physiology and biochemical composition of P. antarctica. In this project, P. antarctica will be collected from the southern Ross Sea and grown in semi-continuous batch cultures for use in experiments at the University of Charleston to investigate the effects of iron availability and irradiance on the growth rate, cellular iron quota, buoyancy, biogenic sulfur production, pigment content, redox-protein expression, and photosynthetic efficiency of P. antarctica. Phaeocystis antarctica is known to have a significant impact on the regional biogeochemical cycles of carbon, nutrient elements and sulfur in the Ross Sea, over timescales ranging from seasonal to interannual. This species may have also played a central role in the inferred basin- scale changes in biogeochemical cycles linked to glacial-interglacial climatic change. Thus it is important to develop a mechanistic understanding of the factors that control the growth, physiology and biochemical composition of P. antarctica, in order to better understand the biogeochemical ecology of the Ross Sea and the wider Southern Ocean, and the possible linkages with regional and global climate. Together with the results of recent and ongoing field and modeling studies, the information provided by these laboratory experiments will substantially improve our ability to predict how the Antarctic region will be affected by and modulate future climate change.