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

本提案的总体目标是通过应用一系列传统和新颖的分子技术，调查真光层中不同关键浮游植物群体的存在与它们对亚热带北大西洋时间序列站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”，即在表层海洋沃茨中以光合作用为媒介将溶解的无机碳转化为颗粒和溶解的有机碳，并随后将其输出到深水，是海洋吸收大气碳的重要驱动力。但是，这种“生物泵”生产，由于它取决于浮游生物的组成和活动，容易受到海洋表层特性长期气候变化的影响，例如温度升高和营养供应变化，特别是在亚热带环流中。亚热带环流及其边界的过渡区在全球碳循环中发挥着重要作用，因为它们面积巨大，单位面积出口产量通常很高。最近的研究表明，生物机制驱动区域到流域尺度的变化，在这些生物群落中的碳输出是远远没有理解，从而限制了我们的能力，机械地解释生物泵，并预测其可能的反应，面对环境变化。为了通过准确评估不同浮游生物群体对总通量的贡献来改善这种情况，研究人员将测试以下两个具体假设：1。长期以来认为大细胞和矿物质测试是向下粒子通量的主要贡献者的观点需要重新评估。我们假设，皮科和nanoplankton（也没有矿物测试）通常是重要的贡献者向下粒子通量在BATS。因此，有助于粒子通量的分类群体的多样性比以前预期的要大。2.分类群对向下粒子通量的相对贡献是物理强迫的函数。我们假设偶发事件（例如，冬季风暴和漩涡）导致沉积浮游植物多样性的减少（例如，与以水柱中更稳定的条件为标志的时期相比，由单一群体（如硅藻）占主导地位。更广泛的影响包括进一步了解浮游植物群体的多样性和生物学，对亚热带环流的碳输出有重大影响，从而促进我们对这些生物群落的生态地球化学区域到流域尺度变化的理解。该项目为本科生和研究生教育提供了新的机会，并为当地高中学生和教师提供研究机会，作为“问生物学家”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学小组合作开展的国际活动。

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.