Collaborative Research: Macrophytes Across the Proterozoic - Phanerozoic Boundary: A Baseline Study of Macroalgae During a Critical Interval in Earth System History

合作研究：横跨元古宙-古宙边界的大型藻类：地球系统历史关键时期大型藻类的基线研究Steven LoDuca和Shuhai Xiao东密歇根大学和弗吉尼亚理工大学现今浅海生态系统中的底栖大型藻类在初级生产和栖息地提供，沉积物生成，运输和积累以及有机碳埋藏方面发挥着关键作用。在更广泛的地球系统背景下，它们在全球碳循环和碳同位素变化的动态中发挥着关键作用。化石数据表明，大型藻类起源于早元古代，但很少有人知道他们跨越元古代-古生界，并进入早古生代。然而，在这一关键时期，大型藻类在生物圈和地球系统动力学中发挥的作用可能比今天更大，这是因为三个因素的汇合：（1）广布的陆表海，（2）缺乏其他海洋植物（海草起源于中生代），（3）在埃迪卡拉-寒武纪过渡期和奥陶纪发生了重大动物多样化事件，主要集中在浅海环境中。因此，在这段时间内，我们缺乏关于大型藻类的信息，这相当于一个严重的知识缺口。该项目将利用大型藻类的化石记录，特别是埃迪卡拉纪和早古生代Konservat-Lagerstätten中大量存在的非钙化形式，开始填补这一空白。具体而言，这将通过多学科，四管齐下的方法来实现：（1）综合分析和鉴定有问题的非矿化类群，其总体形态允许藻类和动物的亲缘关系，包括蓝田物种（Ediacaran）、Burgess页岩、澄江页岩和凯里页岩;（2）形态空间表征，包括形态空间占据、冠层高度和叶状体表面积与体积比的形态测量分析;（3）古生态特征，包括与现代大型藻类群落的比较;（4）碳酸盐、总有机碳和单个大型藻类化石的稳定碳同位素调查，重点是已知产生大量非钙化大型藻类和具有显著碳同位素变化的地层间隔。在本次调查中要解决的关键问题包括：大型藻类经历了重大事件的形态多样化伴随着寒武纪大爆发和奥陶纪辐射（GOBE）事件？早古生代大型藻类群落与埃迪卡拉纪和现代海洋的藻类群落相比如何？在早古生代末期，现代海洋中已知的大型藻类功能型类群是否已经全部存在？陆地植物最初在陆地上定居所引起的营养物质的大量涌入是否引发了早古生代海洋中大型藻类的大量繁殖，以及这种繁殖是否有助于有机碳的埋藏，从而推动了早古生代沉积岩记录中确定的主要碳同位素漂移？这项基线研究将为在这一关键时期对地球生命系统进行更大规模的调查奠定必要的基础，包括早期海洋动物和藻类之间的进化反馈以及不断变化的碳循环动态。该项目的更广泛的影响部分是通过工作中内置的许多教育层面实现的，包括对研究生和本科生的培训以及通过现有STEM计划帮助培训K-12教师的公共宣传工作。该项目还涉及与中国和加拿大古生物学家的国际合作。与该项目直接相关的是，将建立一个名为“史前海洋植物群”的网站，并将其与古生物学门户网站链接，以向公众宣传这项工作的重要性。此外，该项目产生的分类数据将上载到古生物学数据库，所有化石标本将存放在公众可查阅的博物馆。最后，就更广泛的社会利益而言，这项研究是我们寻求了解生物多样性起源的重要组成部分。深刻的过去是我们人类集体遗产的一部分，更好地了解我们的起源会丰富我们所有人。

Collaborative Research: Macrophytes Across the Proterozoic - Phanerozoic Boundary: A Baseline Study of Macroalgae During a Critical Interval in Earth System History Steven LoDuca and Shuhai Xiao Eastern Michigan University and Virginia Tech University Benthic macroalgae in present-day shallow marine ecosystems play a critical role in primary production and habitat provision, sediment generation, transportation, and accumulation, and organic carbon burial. In a broader Earth system context, they play a key role in the dynamics of the global carbon cycle and carbon isotope variations. Fossil data indicate that macroalgae originated during the early Proterozoic, but little is known about them across the Proterozoic-Phanerozoic boundary and into the early Paleozoic. Yet, it is likely that macroalgae during this critical interval played an even larger role in Biosphere and Earth system dynamics than today because of the confluence of three factors: (1) widespread epeiric seas, (2) lack of other marine macrophytes (seagrasses are Mesozoic in origin), and (3) the occurrence of major animal diversification events during the Ediacaran-Cambrian transition and in the Ordovician, which were focused within shallow marine settings. Our lack of information about macroalgae during this timeframe, therefore, amounts to a serious knowledge gap. This project will use the fossil record of macroalgae, particularly noncalcified forms represented abundantly in Ediacaran and early Paleozoic Konservat-Lagerstätten, to begin to fill this gap. Specifically, this will be accomplished through a multidisciplinary, four-pronged approach: (1) Integrative Analysis and Identification of problematic nonmineralized taxa with gross morphologies permissive of both algal and animal affinities, including species from the Lantian (Ediacaran), Burgess Shale, Chengjiang, and Kaili biotas; (2) Morphospace Characterization, including morphometric analyses of morphospace occupation, canopy heights, and thallus surface area to volume ratios; (3) Paleoecological Characterization, including comparisons with modern macroalgal communities; and (4) Stable Carbon Isotope Investigation of carbonate, total organic carbon, and individual macroalgal fossils, focusing on stratigraphic intervals known to yield an abundance of noncalcified macroalgae and to host significant carbon isotope variations. Key questions to be addressed during this investigation include: Did macroalgae experience significant episodes of morphological diversification concomitant with the Cambrian Explosion and Ordovician Radiation (GOBE) events? How do early Paleozoic macroalgal communities compare with those of Ediacaran and modern seas? Did the full array of macroalgal functional-form groups known from modern seas exist by the end of the early Paleozoic? Did massive influxes of nutrients caused by the initial colonization of the land by terrestrial plants trigger colossal blooms of macroalgae in early Paleozoic seas, and could such blooms have contributed to organic carbon burial thus driving major carbon isotope excursions identified in the early Paleozoic sedimentary rock record? This baseline study will establish the foundation necessary for larger-scale investigations of the Earth-Life system during this critical interval, including evolutionary feedback between early marine animals and algae and changing carbon cycle dynamics. The broader impacts of this project are realized, in part, through numerous educational dimensions built into the work, including training for graduate and undergraduate students and public outreach efforts to assist training of K-12 teachers through existing STEM programs. This project also involves international collaborations with Chinese and Canadian paleontologists. Directly related to the project, a website, entitled "Prehistoric Marine Flora," will be constructed and linked to the Paleontology Portal to promote the importance of this work to the general public. In addition, the taxonomic data generated by this project will be uploaded to the Paleobiology Database, and all fossil specimens will be reposited in publicly accessible museums. Finally, in terms of broader benefit to society, this research forms an important part of our quest to understand the origins of our biodiversity. The deep past is part of our collective human heritage, and a better understanding of our origins enriches us all.