High Resolution Paleoecology in a Complex Tropical Ecosystem (Lake Tanganyika, Africa) and the Development of Paleoecological Models for Lake Conservation Biology

小行星9627766 该项目将研究坦噶尼喀湖（一个大型和古老的水生生态系统）底栖生物古群落变化的模式和时间。 在湖的生态相互作用的性质，在湖之前的调查产生了相互矛盾的观点，无论他们是紧密联系和共同进化，或者他们是否是更松散的类群，通过组成物种的个人主义栖息地的要求，甚至更随机的招募从斑块集合种群。这种分歧是生态学家之间关于什么是群落以及群落如何组成的更广泛和长期争论的缩影。 这场争论不仅仅是学术上的，因为湖泊水下保护区的设计隐含着对群落及其组成物种种群的持久性或短暂性的假设。 鉴于其作为生物多样性主要储存库的内在利益（1400种，约600地方性），坦噶尼喀湖提供了一个很好的网站，以解决这个问题，使用古生态技术。 初步研究表明，可以从该湖的近岸沉积物中获得具有丰富多样的动物群的可定年岩心，其地层分辨率为十年（甚至可能是年度）水平。 在湖泊的战略地点采取的核心将采取长期生态研究（十年）和海洋古生态学家通常受到时间平均埋藏过程（千年）的时间跨度之间的界面调查。 这些岩心可以用来回答保护生物学家和理论古生态学家感兴趣的问题。 该项目的主要目标是记录个别底栖物种（甲壳类动物、软体动物和海绵）的局部灭绝和生境斑块退化的模式，并确定每个地点的各种物种历史相互关联的程度。 这将通过取高分辨率古生态记录的湖泊部分的岩心，获得一系列紧密间隔的放射性测年（210 PB和AMS 14 C），以提供准确的岩心年代学，然后以~十年尺度间隔对化石动物群进行采样来实现。 将沿着坦桑尼亚湖沿岸的深度断面（25、50和75米）在分散（河流三角洲）和未受干扰（远离主要河流的台地环境）地点采集一系列岩心，并对底栖生物化石含量和各种古环境指标（沉积学、稳定同位素历史和硅藻古生态学）进行定量分析，以解决以下问题： - 物种群体是同步地还是个体地从地方殖民和消失？ - 物种的出现和消失是否与总体多样性和/或环境变化的变化有关？ - 在没有古环境变化的情况下，特定类群在生物颠覆中是否一贯地相互取代？ - 坦噶尼喀湖的古生物学记录是否更好地支持极端生态位专门化的模式 和物种整合（在相对恒定的环境条件下， 条件或物种组合的连续非平衡重配之一？ - 地方性灭绝和地方性化事件自然发生的速度如何，地方性地方病种群的“永久性”或临时性如何？ - 观察到的社区凝聚力的存在或不存在对在湖泊邻近地区建立水下保护区有何影响？ 群落古生态学家和保护生物学家分享了大量关于群落结构和稳定性的问题，尽管这两个领域之间的明确联系很少被阐明。 这里提出的研究有可能展示这些联系的方式。

9627766 Cohen This project will examine the patterns and timing of benthic paleocommunity change in Lake Tanganyika, a large and ancient aquatic ecosystem. Prior investigations in the lake have yielded conflicting views of the nature of ecological interactions in the lake, whether they are tightly linked and coevolved, or whether they are much looser assortments of taxa, formed either through the individualistic habitat requirements of components species or even more randomly by recruitment from patchy metapopulations. This disagreement is a microcosm of the broader and long-standing argument among ecologists of what a community is and how it is assembled. The dispute is not merely academic, since the design of underwater reserves in a lake implicity requires assumptions about the permanence or ephemerality of communities and their component species' populations. Given its intrinsic interest as a major reservoir of biodiversity (1400 spp., ~600 endemic), Lake Tanganyika provides an excellent site to address this problem using paleoecolgical techniques. Preliminary studies have demonstrated that dateable cores with abundant and diverse faunas can be obtained from the nearshore sediments of this lake, with stratigraphic resolution on the decadal (and perhaps even annual) level. Cores taken at strategic localities in the lake will be taken to create an interface between the time-scales investigated by Long Term Ecological Research Studies (decadal) and the time spans to which marine paleoecologist are normally constrained by time-averaging taphonomic processes (millenia). These cores can be used to answer questions of interest to both conservation biologist and theoretical paleoecologists. The primary goal of this project will be to document patterns of local extinction and recolonization of habitat patches by individual benthic species (crustaceans, molluscs and sponges) and to determine the degree to which the various species histories at each site are interrelated. This will be ach ieved by coring portions of the lake where high resolution paleoecological records can be obtained, obtaining a closely-spaced series of radiometric dates (210 PB and AMS 14C) to provide an accurate chronology of the cores, and then sampling the fossil fauna at ~decadal scale intervals. A series of cores at both distrurbed (river delta) and undisturbed (platform environments away from major rivers) localities will be taken along the Tanzanian coast of the lake along depth transects (25,50 and 75m) and analyzed quantitatively for fossils benthos content and various paleoenvironmental indicators (sedimentology, stable isotope history and diatom paleoecology) to address the following questions: -Do species groups colonize and dissappear from localities in synchrony or individualistically? -Are appearances and disappearances of species correlated with changes in overall diversity and/or environmental shifts? -Do particular clusters of taxa replace each other consistently in biotic overturn, in the absence of paleoenvironmental change? -Does the paleobiologic record in Lake Tanganyika better support a model of extreme niche specialization and species integration (little relative biotic overturn, under relatively constant environmental conditions or one of continuous non-equilibrium reassortment of species assemblages? -At what rate do local extinction and recolonization events naturally occur and how "permanent" or temporary are populations of local endemics? -What are the implications of the observed presence or absence of community cohesion for the establishment of underwater reserves in adjacent parts of the lake? Community paleoecologist and conservation biologists share a host of questions about community structure and stabilty, although explicit linkages between the two fields have rarely been articulated. The research proposed here has the potential to demonstrate ways in which these linkages can be made.