Collaborative Research: Grazing and Iron Controls of Diatom Blooms in the Arabian Sea

合作研究：阿拉伯海硅藻华的放牧和铁控制

• 批准号: 0825598
• 负责人: Sharon Smith
• 金额: $ 47.94万
• 依托单位: University of Miami
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-01-01 至 2013-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0825598&HistoricalAwards=false
• 关键词: Collaborative; Research; Grazing; Iron; Controls

The Arabian Sea is important in global C and N budgets because of its high rates of annual primary production, its extensive zone of oxygen depletion and denitrification, and its expected strong response to global warming via ocean-atmosphere feedback to monsoon winds and upwelling intensity, especially the Oman Upwelling, driven by the SW Monsoon. The paradox of the Arabian Sea is that it produces a very weak and delayed phytoplankton response compared to other physically dynamic upwelling systems. Thick blooms of large diatoms are uniquely not evident in the Arabian Sea despite apparently abundant nutrients, seed stocks and favorable hydrographic conditions. The subdued response shifts carbon export offshore of the coastal upwelling area and delays major flux events until the latter stages of the SW Monsoon, with important implications for the western boundary of the oxygen minimum zone. This work will test the hypotheses that grazing interactions, iron limitation, or both, control diatoms and, more generally, phytoplankton biomass, production and the delayed flux characteristics of the Arabian Sea. Grazer control was a major, but as yet untested, conclusion of the US JGOFS program. In 2007, one of the investigators found that a large region of the central and southern Arabian Sea was Fe-limited during the SW Monsoon, consistent with recent modeling studies. Iron limitation may exacerbate grazing regulation, and integration of Fe and grazing experiments is a central part of the work plan. A cruise to the Oman upwelling region during the SW Monsoon in 2010 will include iron and nutrient biogeochemistry, plankton community structure and dynamics, taxon-specific estimates of phytoplankton growth and production, grazing contributions of micro- and mesozooplankton, with a focus on large copepods (Calanoides carinatus, Subeucalanus crassus, Paraeucalanus sewelli), whose life histories, abundance and size are consistent with a top-down regulatory role. The approach will involve assessment of net community rates of changes following a Lagrangian drift array and contemporaneous in situ studies of phytoplankton growth, production, micro- and mesozooplankton grazing. Shipboard experiments will address the response of phytoplankton to added Fe and Si and reproductive responses of dominant large grazers to food supply, their ability to modulate the grazing impacts of micro-herbivores and their direct and indirect effects on lower trophic levels. The sampling program will resolve the abundances, depth distribution and lipid contents of major grazers during a critical time of year (August-September) when there is little previous data and as the animals are preparing to leave surface waters for their seasonal diapause migration to mesopelagic depths. Grazing control in the Arabian Sea, if confirmed, will be a unique example of top-down regulation of a significant open-ocean ecosystem with important consequences for carbon and nitrogen cycling. Furthermore, understanding the potential limiting effects of Fe availability will allow us to better anticipate how the ocean ecology and biogeochemistry will respond to changes in climate and monsoon intensity that affect dust fluxes from the surrounding arid landmasses.The most recent IPCC report cites changes in monsoon intensity as a likely impact of the present trend in planetary warming. This project seeks to understand ecological, biological and geochemical constraints on production, carbon cycling and export in the upwelling system so that the effects of climate changes can be better anticipated and modeled. This project will also contribute to the oceanographic infrastructure of India and Oman, both critical US partners in the Indian Ocean, as well as continue ongoing activities in public outreach, K-12 education, broadening undergraduate educational opportunities, for example through the MATE program, and graduate training of diversity students in marine science.

阿拉伯海在全球C和N预算中很重要，因为其年度生产率很高，其广泛的氧气耗尽和反硝化区域以及通过海洋 - 大气向季风风和上升强度，尤其是由SW Monsoon驱动的阿曼上升强度的海洋 - 大气向全球变暖的预期反应。阿拉伯海的悖论是，与其他动态动态上升流相比，它产生的浮游植物反应非常弱且延迟。尽管营养丰富，种子库存和有利的水文条件，但在阿拉伯海中，大硅藻的厚花并不明显。柔和的响应将沿海上升流域的碳出口转移，并延迟了主要的通量事件，直到SW季风的后期阶段，对氧最小区域的西部边界具有重要意义。这项工作将测试放牧相互作用，铁的限制或控制硅藻的假设，更普遍地是浮游植物生物量，生产和阿拉伯海的延迟通量特征。 Grazer控制是美国JGOFS计划的重大但尚未测试的。 2007年，其中一名研究人员发现，在SW季风期间，阿拉伯海中部和南部的大部分地区是Fe限制的，这与最近的建模研究一致。铁的限制可能会加剧放牧调节，而Fe和放牧实验的整合是工作计划的核心部分。 A cruise to the Oman upwelling region during the SW Monsoon in 2010 will include iron and nutrient biogeochemistry, plankton community structure and dynamics, taxon-specific estimates of phytoplankton growth and production, grazing contributions of micro- and mesozooplankton, with a focus on large copepods (Calanoides carinatus, Subeucalanus crassus, Paraeucalanus Sewelli），其生活历史，丰度和规模与自上而下的监管作用一致。该方法将涉及评估拉格朗日漂移阵列和同时研究浮游植物生长，生产，微观和中龙兰克顿放牧后的净社区变化率。船上实验将解决浮游植物对增加Fe和Si的反应，以及主要的大放牧者对食物供应的生殖反应，它们调节微生动物的放牧影响及其直接和间接影响对低营养水平的影响。抽样计划将在一年中的关键时期（8月至9月）中解决主要放牧者的丰度，深度分布和脂质含量，当时几乎没有以前的数据，并且随着动物准备离开地表水以进行季节性的抑郁症迁移到中层状深度。如果得到证实，阿拉伯海的放牧控制将是对重要开放海洋生态系统自上而下的独特例子，对碳和氮循环产生了重要影响。此外，了解FE可用性的潜在限制效应将使我们能够更好地预期海洋生态学和生物地球化学将如何应对气候和季风强度的变化，从而影响周围的干旱地陆地的灰尘通量。最新的IPCC报告说，季风强度的变化可能会影响当前的趋势，这可能会影响星球温暖的趋势。该项目旨在了解上升流系统中生产，碳循环和出口的生态，生物学和地球化学限制，以便可以更好地预期和建模气候变化的影响。该项目还将为印度和阿曼的海洋基础设施做出贡献，包括印度洋的关键美国合作伙伴，以及继续在公共宣传，K-12教育，扩大本科教育机会的持续活动，例如通过伴侣计划以及对海洋科学多样性学生的研究生培训。