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

智力优势：在南大洋的大部分地区，铁和光照被认为对南极洲棕囊藻和硅藻这两个主要浮游植物种群的水华发生的时间和位置起着重要的控制作用。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范围特征，规定了硅藻相对于南极洲生长更高的铁需求，并允许南极洲在低光照下有更高的生长速度。然而，与这些模型中使用的参数有关的不确定性很大，特别是关于浮游植物铁参数，这些参数通常被指定为静态值。最近对殖民地南极洲的实验室实验结果表明，该物种对铁的需求可能相对较高，并且似乎随着辐射的变化而强烈变化。在这个项目中，研究人员将利用实验室实验来量化代表罗斯海南部开阔水域、冰缘和海冰环境的硅藻物种的铁需求，包括纤细海藻、拟亚曲藻、圆柱藻和冰舟藻。这些实验数据将被用来检验一系列假说，这些假说涉及铁的可获得性、辐射和UV-B暴露对生长速度、二甲基硫磺酸二甲酯和二甲基硫化物的产生、细胞色素组成以及对大量营养素的相对吸收的影响。此外，研究人员将进行初步的“藻类竞争实验”，在该实验中，将考察含有硅藻和南极洲棕囊藻的混合群落在有和没有UV-B照射的情况下，作为铁和辐射的函数的生长情况。更广泛的影响：这项研究将提供建立健全的、机械上准确的南大洋生态系统和生物地球化学数值模型所需的定量信息。该项目还将通过研究生和本科生直接参与实验室研究，以及通过计划的针对K-12学生和普通公众的外联活动，包括在百慕大和南卡罗来纳州的讲座，以及与一组K-12科学教师协商开发网络材料，在几个层面上作出教育贡献。

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.