Tracking Arctic marine productivity across the Holocene - Anthropocene transition using novel compound-specific stable isotope techniques

我的研究项目的总体目标是开发、测试和应用新的稳定同位素技术，以跟踪北极和亚北极海洋初级生产力的长期变化。到2040年，北极夏季海冰预计将完全消失，这可能是近1300万年来的第一次。目前还不清楚，在未来无冰的北极，初级生产力是会增加还是会减少。这对于预测渔业产量和通过将二氧化碳生物封存到深海来减缓温室气体排放具有紧迫的全球重要性。冰盖的减少应导致光合作用潜力的增加；然而，营养限制和高产冰藻栖息地的丧失可能会抵消更长无冰生长季节所带来的生产力增长。我们对控制海洋生产力的物理-生物过程和反馈的理解受到以下因素的限制：除了夏季的一个狭窄窗口外，很难进入偏远的北极环境；卫星遥感器无法看到水柱深处25米以下的地方；以及严重缺乏长期（几十年）的科学观测。我的研究项目从两个关键方面直接解决了这些对科学进步的持续挑战。首先，我们利用深海珊瑚骨骼中包含的年度分辨率古记录，这些骨骼以最近出口的初级生产力的下沉通量为食。通过将这些珊瑚记录与更传统的沉积物岩心记录相结合，将产生北极水域前所未有的长度和分辨率的古记录。其次，我们利用珊瑚和沉积物中保存的氨基酸碳氮稳定同位素分析的突破性解释潜力。这种新颖的方法超越了传统的体积同位素方法，提供了一种独立跟踪海洋食物网基础的四个关键过程的方法：营养来源、自养生物群落组成、生物营养位置和微生物降解。以年分辨率和百年时间跨度重建这些变量，将使我们能够检验关于海冰条件变化对养分有效性和初级生产力影响的假设。这项研究建立在创新和有影响力的古生态重建的坚实记录之上，这对于理解、减缓和适应气候变化至关重要。

The overall goal of my research program is to develop, test and apply novel stable isotopic techniques for tracking long-term changes in primary productivity in the Arctic and sub-Arctic Oceans. By the year 2040, Arctic summer sea ice is projected to disappear completely for the first time in perhaps the last 13 million years. It remains unclear if primary productivity will increase or decrease in a future ice-free Arctic. This has urgent global importance for predicting fisheries yields and for mitigation of greenhouse gas emissions via biological sequestration of CO2 to the deep ocean. Loss of ice cover should lead to increases in photosynthetic potential; however, nutrient limitation and loss of habitat for highly productive ice algae could negate any gains in productivity made from longer ice-free growing seasons. Our understanding of physical-biological processes and feedbacks controlling marine productivity are limited by difficulty accessing the remote Arctic environment in all but a narrow window of summer, satellite remote sensors that cannot see deeper than 25 m into the water column, and an acute lack of long-term (multi-decadal) scientific observations. My research program directly addresses these ongoing challenges to scientific progress in two key ways. First, we make use of annual resolution paleo-records contained in the skeletons of deep-sea corals that feed on the sinking flux of recently exported primary productivity. By combining these coral records with those from more traditional sediment cores, paleo-records of unprecedented length and resolution for Arctic waters will be generated. Second, we leverage the breakthrough interpretive potential of carbon and nitrogen stable isotopic analysis of amino acids preserved in corals and sediments. This novel methodology goes beyond traditional bulk isotope methods to provide a means for independently tracking four key processes at the base of marine foodwebs: nutrient source, autotroph community composition, organism trophic position, and microbial degradation. Reconstruction of these variables at annual resolution and over multi-centennial timespans will allow us to test hypotheses on the effect of changing sea ice conditions on nutrient availability and primary productivity. This research builds on a solid track record of innovative and impactful paleo-ecological reconstructions, which are essential for understanding, mitigating and adapting to climate change.