Collaborative Research: Impact of Solar Radiation and Nutrients on Biogeochemical Cycling of DMSP and DMS in the Ross Sea, Antarctica

在南部的春季和初夏，南大洋地区浮游植物大量繁殖。其中一种主要的浮游植物是南极褐藻，它是有机硫化合物二甲基磺酰丙酸酯（DMSP）的多产生产者，而褐藻华与世界上一些最高浓度的DMSP及其挥发性降解产物二甲基硫化物（DMS）有关。硫以DMS的形式从海洋转移到大气，可以影响降水的化学性质，影响云的性质，并可能影响气候。DMSP和DMS在数量上也是许多海洋食物网中碳、硫和能量流动的重要组成部分，尽管关于高纬度系统中这些过程的信息很少。该项目将研究太阳辐射和铁循环如何影响浮游植物产生DMSP和DMS，以及微生物食物网随后对这些不稳定形式的有机物的利用。将在实地实验和现场观测中检验四个相互关联的假设：1)太阳辐射，包括由于季节性臭氧消耗而增强的UV-B，在决定罗斯海DMS的生态系统净产量方面起着重要作用；2)由于浮游生物群落暴露于高剂量太阳辐射，浅层混合层的发育促进了表层DMS的积累；3) DMSP的产生和周转是极地食物网碳硫通量的重要组成部分；4)水华的发展和由此产生的养分消耗（如铁）将导致DMSP的高产率和高DMS浓度和大气通量。这项研究的结果将大大提高对极地水域DMSP和DMS浓度的潜在控制机制的理解，从而提高我们预测从这一重要气候区域到大气的DMS通量的能力。Drs。Kieber和Kiene积极地让高中生、本科生和研究生参与他们的研究，并参与了针对代表性不足的群体（NSF-REU和美国化学学会- seed）的正式项目。这个项目将继续这种教育外展。pi还教授本科和研究生课程，并将研究经验纳入他们的课堂将丰富学生的学习经验。

Areas of the Southern Ocean have spectacular blooms of phytoplankton during the austral spring and early summer. One of the dominant phytoplankton species, the haptophyte Phaeocystis antarctica, is a prolific producer of the organic sulfur compound dimethylsulfoniopropionate (DMSP) and Phaeocystis blooms are associated with some of the world's highest concentrations of DMSP and its volatile degradation product, dimethylsulfide (DMS). Sulfur, in the form of DMS, is transferred from the oceans to the atmosphere and can affect the chemistry of precipitation and influence cloud properties and possibly climate. DMSP and DMS are also quantitatively significant components of the carbon, sulfur and energy flows in many marine food webs, although very little information is available on these processes in high latitude systems. This project will study how solar radiation and iron cycling affect DMSP and DMS production by phytoplankton, and the subsequent utilization of these labile forms of organic matter by the microbial food web. Four interrelated hypotheses will be tested in field-based experiments and in situ observations: 1) solar radiation, including enhanced UV-B due to seasonal ozone depletion, plays an important role in determining the net ecosystem production of DMS in the Ross Sea; 2) development of shallow mixed layers promotes the accumulation of DMS in surface waters, because of enhanced exposure of plankton communities to high doses of solar radiation; 3) DMSP production and turnover represent a significant part of the carbon and sulfur flux through polar food webs; 4) bloom development and resulting nutrient depletion (e.g., iron) will result in high production rates of DMSP and high DMS concentrations and atmospheric fluxes. Results from this study will greatly improve understanding of the underlying mechanisms controlling DMSP and DMS concentrations in polar waters, thereby improving our ability to predict DMS fluxes to the atmosphere from this important climatic region. Both Drs. Kieber and Kiene actively engage high school, undergraduate and graduate students in their research and are involved in formal programs that target underrepresented groups (NSF-REU and the American Chemical Society-SEED). This project will continue this type of educational outreach. The PIs also teach undergraduate and graduate courses and incorporation of research experiences into their classes will enrich student learning experiences.