Collaborative Research: Quantifying the Effects of Iron and Light on the Growth of Diatoms from the Ross Sea, Antarctica

智力优点：在南大洋的大部分地区，铁和辐照度被认为是对两大浮游植物群体（南极棕囊藻和硅藻）水华的时间和位置的主要控制因素。 最近的数值模拟研究模拟了罗斯海南部藻类生物量和物种组成的大尺度特征，规定了硅藻相对于P anapartica的生长需要更高的铁，并允许P. anapartica在低辐照下具有更高的生长速率。然而，有很大的不确定性与这些模型中使用的参数化，特别是关于浮游植物铁参数，这是典型的静态值。最近的实验室实验结果与殖民P. anaitica表明，该物种的铁的需求可以相对较高，并出现强烈的变化作为一个功能的辐照度。在该项目中，研究人员将使用实验室实验来量化罗斯海南部开放水域，冰缘和海冰环境的硅藻物种的铁需求，包括Thalassiosira gracilis，Pseudo-nitzschia subcurvata，Fragilariopsis cylindrus和Navicula glaciei。实验数据将被用来测试一些假设的影响，铁的可用性，辐照度和UV-B照射对生长速度，生产的二甲基磺基丙酸酯和二甲硫醚，细胞色素的组成，和相对吸收的常量营养素。此外，调查人员将进行初步的“藻类竞争实验”，其中将检查含有硅藻和殖民性南极棕囊藻的混合组合的生长，作为铁和辐照度的函数，有和没有紫外线-B照射。更广泛的影响：该研究将提供定量信息，以构建南大洋生态系统和海洋地球化学的强大，机械精确的数值模型。该项目还将通过研究生和本科生直接参与实验室研究，并通过针对K-12学生和公众的计划外展活动，包括在百慕大和南卡罗来纳州的讲座，以及与K-12科学教师协商编写网络材料，在多个层面上做出教育贡献。

Intellectual merit: In much of the Southern Ocean, iron and irradiance are thought to exert major controls on the timing and location of blooms of the two major phytoplankton groups, Phaeocystis antarctica and diatoms. Recent numerical modeling studies have simulated the broad-scale features of algal biomass and species composition in the southern Ross Sea, by prescribing a higher iron requirement for the growth of diatoms relative to P antarctica and by allowing higher growth rates by P. antarctica under low irradiance. However, there are large uncertainties associated with the parameterizations used in these models, particularly with regard to phytoplankton iron parameters, which are typically assigned static values. Results of recent laboratory experiments with colonial P. antarctica suggest that the iron requirement of this species can be relatively high, and appears to vary strongly as a function of irradiance. In this project, the investigators will use laboratory experiments to quantify the iron requirements of diatom species that are representative of open-water, ice-edge and sea-ice environments of the southern Ross Sea, including Thalassiosira gracilis, Pseudo-nitzschia subcurvata, Fragilariopsis cylindrus and Navicula glaciei. The experimental data will be used to test a number of hypotheses concerning the effects of iron availability, irradiance and UV-B exposure on growth rates, production of dimethylsulfoniopropionate and dimethylsulfide, cellular pigment composition, and the relative uptake of macronutrients. In addition, the investigators will conduct preliminary "algal competition experiments", in which the growth of mixed assemblages containing both diatoms and colonial Phaeocystis antarctica will be examined, as a function of iron and irradiance, with and without UV-B exposure. Broader impacts: The research will provide quantitative information that is required to construct robust, mechanistically-accurate numerical models of Southern Ocean ecosystems and biogeochemistry. This project also will make educational contributions at several levels, through the direct involvement of graduate and undergraduate students in laboratory research, and through planned outreach activities aimed at K-12 students and the general public, including lecture presentations in Bermuda and South Carolina, and the development of web materials in consultation with a group of K-12 science teachers.