Collaborative Re:Temporal resolution in benthic assemblages: assessing and modeling the roles of burial dynamics, seafloor type, and intrinsic factors using (un)natural experiments

协作Re：海底组合中的时间分辨率：使用(联合国)自然实验评估和模拟埋葬动力学、海底类型和内在因素的作用芝加哥大学克拉克·亚历山大斯基德威尔，斯基德韦海洋学研究所生物学家越来越认识到需要对沿海环境中物种的存在和丰富性进行更长期的视角，以评估人类活动如何改变这些重要的生态系统，在大多数地区，这早在20世纪初定量调查和20世纪70年代联邦规定的生物监测出现之前就开始了。非常年轻的化石记录？也就是说，来自过去几十年、数百年和数万年的骨骼遗骸，嵌入在沉积记录的上部几米内？为在整个文化/工业发展历史上重建生态系统的变化，以及获取对制定恢复目标至关重要的真正自然条件的信息，提供了一种有希望的手段。然而，为了自信地将这些地质上年轻的古生物数据与传统的新生物数据结合起来，我们需要了解生物信息是如何随着贝利遗骸的逐渐自然埋葬而改变的。过去20年的研究发现，在风暴和动物搅动的海床最高处几厘米处存在的软体动物死亡组合(文蛤和蜗牛壳)可能包括一些相当古老的贝壳(数千年前，特别是在开放的大陆架上)，但主要是在上一次(最近)？城市？一个世纪，尤其是最近几十年。因此，来自这个混合层的死亡集合显然是时间平均的，但最强的信号来自骨骼积累的最后阶段，就像摄影时间曝光产生的移动物体的模糊轨迹一样，其最终位置被捕捉到快照般的清晰。在这里，在美国国家科学基金会的资助下，我们将首次测试骨骼组合在逐步埋藏到全新世沉积记录的更深、更永久的层中时保持这种时间分辨率水平的程度，在这些层中，组合不再因新的贝壳输入而刷新，并受到不同化学状态的影响。我们将利用对海底动物和南加州大陆架环境条件的广泛先验知识，对被认为控制骨骼积累的关键因素进行一系列观测实验，即：(1)贝壳材料的内在耐久性(侧重于六个关键属的双壳类，贝壳矿物学和微结构不同)，(2)沉积物积累的速度和类型(陆源泥沙，加上富含贝壳的海床，没有沉积物)，以及(3)风暴和穴居动物混合沉积物的速度和深度，因子2和3使用放射性同位素方法进行量化。贝壳年龄将基于放射性碳校准的氨基酸外消旋测年，我们已经确定在这一地区工作得很好。关于时间分辨率如何随埋藏变化的数据将通过对长(3-4米)沉积岩芯中的一系列层位进行贝壳测年而产生。我们将在帕洛斯韦尔德斯大陆架上含DDT的废水和历史上未被污染的海底，沿着已知的沉积物毒性遗留梯度提取这些岩芯，提供一种不自然的？生物扰动效应的实验研究。利用随机模拟和贝龄频率分布的似然分析以及对实验结果的常规统计分析，该项目将确定决定贝壳保存的主要机制，这与深层和近时间化石记录中的骨骼组合的生态保真度和时间分辨率有关。更广泛的影响是，我们将制定和完善合并来自古生物和新生物来源的生物信息的协议，作为新兴的保护古生物学新领域的一部分。研究论文将发表在海洋生物和污染期刊上，而不仅仅是地球科学期刊上，以促进科学一体化。我们已经与几个负责环境管理的地区机构的科学家建立了合作关系，他们将通过现场会谈了解最新的研究结果。来自我们岩心的存档骨骼组合将为未来不同类型的研究(例如，形态、骨骼年代学、同位素、分子)提供新的资源，特别是当与我们已经从过去(20世纪70年代)和正在进行的(2003？目前)对生活架群落的调查和生物监测。该项目将为博士后学者以及来自历史悠久的黑人院校(萨凡纳州立大学)的本科生和研究生助理提供实地和实验室经验。我们还将开发一项实验室练习，供当地高中和两年或四年制大学使用，内容包括南加州海洋湾的历史生态以及沉积岩芯在环境和生态分析中的能力。该区域对沿海环境质量有着强烈的公众兴趣和政府承诺，因此拥有良好的公共宣传基础设施。

Collaborative Re:Temporal resolution in benthic assemblages: assessing and modeling the roles of burial dynamics, seafloor type, and intrinsic factors using (un)natural experimentsSusan Kidwell, University of ChicagoClark Alexander, Skidaway Institute of OceanographyBiologists increasingly appreciate the need for longer term perspectives on the presence and abundance of species in coastal environments in order to evaluate how these important ecosystems have been altered by human activities, which in most areas began well before the advent of quantitative surveys in the early 20th century and federally mandated biomonitoring in the 1970s. Very young fossil records ? that is, skeletal remains from the last few decades, centuries, and tens of millennia, embedded within the upper few meters of the sedimentary record ? offer a promising means both of reconstructing changes in ecosystems over the full history of cultural/industrial development and of acquiring the information on truly natural conditions that is essential to developing restoration targets. However, to confidently merge these geologically young paleontological data with conventional neo-biological data, we need to understand how, if at all, biological information is altered with the progressive, natural burial of shelly remains. Research over the last 20 years finds that molluscan death assemblages (clam and snail shells) present within the uppermost, storm- and animal-stirred few centimeters of the seabed can include some fairly old shells (thousands of years old, especially on open continental shelves), but are strongly dominated by individuals that died during the last (most recent) ?urban? century and especially the last few decades. Death assemblages from this mixed layer are thus clearly time-averaged, but the strongest signal is from the final stages of skeletal accumulation, much like a photographic time-exposure produces a somewhat blurry track of a moving object whose final position is captured with snapshot-like clarity. Here, with NSF funding, we will test for the first time the extent to which skeletal assemblages retain this level of temporal resolution as they undergo progressive burial into deeper, more permanent layers of the Holocene sedimentary record, where the assemblage is no longer refreshed by new shell input and is subject to different chemical regimes. We will leverage extensive prior knowledge of seafloor animals and environmental conditions on the southern California continental shelf to conduct a series of observational experiments on the key factors thought to control skeletal accumulation, namely (1) the intrinsic durability of shell material (focus on six key genera of bivalves, differing in shell mineralogy and microstructure), (2) rates and types of sediment accumulation (land-derived mud and sand, plus shell-rich seabeds deprived of sediment), and (3) rates and depths of sediment mixing by storms and burrowing animals, with factors 2 and 3 quantified using radioisotopic methods. Shell ages will be based on radiocarbon-calibrated amino-acid racemization dating, which we have already determined works well in this region. Data on how temporal resolution changes with burial will be generated by dating sets of shells from a series of horizons in long (3-4 m) sedimentary cores. We will take these cores at sites both along the known legacy gradient of sediment toxicity from DDT-charged wastewater effluents on the Palos Verdes shelf and from historically uncontaminated seafloors, providing an ?unnatural? experiment on the effects of bioturbation. Using stochastic simulations and likelihood analysis of shell-age frequency distributions as well as conventional statistical analysis of experimental results, this project will identify the dominant mechanisms that determine shell preservation, which is relevant to the ecological fidelity as well as the temporal resolution of skeletal assemblages in both the deep- and near-time fossil records. Of even broader implications, we will develop and refine protocols for merging biological information from paleontological and neo-biological sources, as part of the burgeoning new field of conservation paleobiology. Research papers will be published in marine biological and pollution journals rather than only earth science journals to promote scientific integration. We already have a cooperative relationship with scientists from several regional agencies charged with environmental management, who will be kept up to date with research results by talks on site. Archived skeletal assemblages from our cores will constitute a new resource for future studies of diverse types (e.g., morphology, sclerochronology, isotopes, molecules), particularly when combined with extensive mixed-layer death assemblages that we have already archived from past (1970s) and ongoing (2003 ? present) surveys and biomonitoring of living shelf communities. The project will provide field and lab experience for a post-doctoral scholar and for undergraduate and graduate student assistants drawn from an historically black institution (Savannah State). We will also develop a lab exercise for use in local high schools and 2-year or 4-year colleges on the historical ecology of the southern California marine bight and the power of sedimentary cores for environmental and ecological analysis. This region has strong public interest and governmental commitment to coastal environmental quality, and thus has a good existing infrastructure for public outreach.