Composition of the plankton community and its contribution to particle flux in the Sargasso Sea

这项建议的总体目标是，通过应用一系列传统和新的分子技术，调查真光层不同关键浮游植物种群的存在与它们对北大西洋亚热带时间序列站点BATS(百慕大大西洋时间序列研究)粒子通量的贡献之间的联系。生物泵是在光合作用的作用下，将表层海水中溶解的无机碳转化为颗粒状和溶解有机碳，然后输出到深水，是海洋吸收大气碳的重要驱动力。但是，这种“生物泵送”的生产依赖于浮游生物的组成和活动，容易受到表层海洋性质的长期气候变化的影响，例如温度升高和营养物质供应的变化，特别是在亚热带环流。亚热带气旋及其边界的过渡带在全球碳循环中发挥着重要作用，因为它们的规模巨大，单位面积的出口产量普遍较高。最近的研究表明，在这些生物群落中，推动区域到流域尺度碳输出差异的生物机制还远未被了解，从而限制了我们从机械上解释生物泵并预测其在面对环境变化时可能的反应的能力。为了通过准确评估不同浮游生物群体对总体通量的贡献来改善这种情况，研究人员将检验以下两个具体假设：1.需要重新评估长期以来认为大细胞和那些进行矿物测试的细胞是向下粒子通量的主要贡献者的观点。我们假设，微微浮游生物和纳米浮游生物(也是那些没有进行矿物测试的浮游生物)通常是BATS向下的粒子通量的重要贡献者。因此，对颗粒通量做出贡献的分类群的多样性比之前预期的要大。2.分类群对向下颗粒通量的相对贡献是物理强迫的函数。我们假设，与水体条件更稳定的时期相比，间歇性事件(例如冬季风暴和漩涡)导致沉积浮游植物的多样性减少(例如，由硅藻等单一类群占优势)。更广泛的影响包括进一步了解对副热带环流碳输出有重大影响的浮游植物种群的多样性和生物学，从而促进我们对这些生物群生物地球化学中区域到盆地尺度的变异性的理解。该项目为本科生和研究生教育提供了新的机会，并为当地高中生和教师提供了研究机会，这是“生物学家问答”倡议的一部分。该项目还包括与西班牙巴塞罗那的一个分子生态组织合作的国际组成部分。

The overall objective of this proposal is to investigate linkages between the presence of different key groups of phytoplankton in the euphotic zone and their contribution to particle flux at the subtropical North Atlantic time-series station BATS (Bermuda Atlantic Time-series Study) by applying a range of traditional and novel molecular techniques. The 'biological pump', the photosynthetically mediated transformation of dissolved inorganic carbon into particulate and dissolved organic carbon in surface ocean waters and its subsequent export to deep water, is a significant driver of the atmospheric carbon uptake by the oceans. But this "biologically pumped" production, inasmuch as it depends on the composition and activity of planktonic organisms, is susceptible to long-term climatic changes in surface ocean properties such as increased temperature and changes in nutrient supply, especially in subtropical gyres. The sub-tropical gyres and the transition zones at their boundaries play an important role in the global carbon cycle because of their vast size and generally high per area export production. As evidenced in recent studies, the biological mechanisms driving regional to basin scale variability in carbon export in these biomes is far from understood, thus limiting our ability to mechanistically explain the biological pump and to predict its possible responses in the face of environmental change. In an effort to improve this situation with an accurate assessment of the contribution of different plankton groups to overall fluxes, the investigators will test the following two specific hypotheses:1. The long held notion that large cells and those with mineral tests are major contributors to downward particle flux needs to be re-evaluated. We hypothesize that pico and nanoplankton (also those without mineral tests) are generally important contributors to downward particle flux at BATS. Consequently, the diversity of taxonomic groups contributing to particle flux is greater than previously expected. 2. The relative contribution of taxonomic groups to downward particle flux is a function of physical forcing. We hypothesize that episodic events (e.g., winter storms and eddies) lead to a reduction in diversity of sedimenting phytoplankton (e.g., dominance by a single group such as diatoms) compared to periods marked by more stable conditions in the water column. The broader impacts include furthering knowledge of the diversity and biology of phytoplankton groups that have a significant impact on the carbon export in subtropical gyres, thereby advancing our understanding of regional to basin scale variability in the biogeochemistry of these biomes. The project provides new opportunities for undergraduate and graduate education, as well as offer research opportunities to local high school students and teachers as part of the "Ask-a-Biologist" initiative. The project also includes an international component through collaboration with a molecular ecology group in Barcelona, Spain.