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

协作回复：底栖生物组合的时间分辨率：使用（非）自然实验评估和模拟埋藏动力学、海底类型和内在因素的作用。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程度进行长期的展望，以评估这些重要的生态系统是如何被人类改变的。这些活动在大多数地区早在世纪早期定量调查和20世纪70年代联邦政府授权的生物监测出现之前就开始了。很年轻的化石记录？也就是说，过去几十年，几个世纪和几万年的骨骼遗骸，嵌入沉积记录的上部几米？提供了一种有希望的手段，既可以重建整个文化/工业发展历史上生态系统的变化，又可以获得对制定恢复目标至关重要的真正自然条件的信息。然而，为了自信地将这些地质学上年轻的古生物学数据与传统的新生物学数据相结合，我们需要了解生物信息是如何随着贝壳遗骸的逐渐自然埋葬而改变的。过去20年的研究发现，在海底最上面的几厘米处，风暴和动物搅动的软体动物死亡组合（蛤蜊和蜗牛壳）可以包括一些相当古老的贝壳（数千年的历史，特别是在开放的大陆架上），但主要是由最近（最近）死亡的个体主导。城市？世纪，尤其是最近几十年。因此，来自这个混合层的死亡组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，就像摄影的时间曝光产生了一个移动物体的模糊轨迹，其最终位置以快照般的清晰度被捕获。在这里，与美国国家科学基金会的资金，我们将首次测试在何种程度上骨骼组合保持这种水平的时间分辨率，因为他们经历了渐进式埋藏到更深，更永久的层全新世沉积记录，在那里的组合不再刷新新的壳输入，并受到不同的化学制度。我们将利用对南加州大陆架海底动物和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察实验，即（1）壳体材料的内在耐久性（重点介绍双壳类的六个主要属，壳矿物学和显微结构各不相同），（2）沉积物积累的速度和类型（陆源泥沙，加上没有沉积物的富壳海床），（3）风暴和穴居动物混合沉积物的速度和深度，用放射性同位素方法对因子2和因子3进行量化。贝壳年龄将基于放射性碳校准的氨基酸消旋测年，我们已经确定这在这个地区很有效。将通过对长（3-4米）沉积岩心中一系列层位的贝壳进行年代测定，获得时间分辨率如何随埋藏而变化的数据。我们将采取这些核心的网站都沿着已知的遗产梯度沉积物的毒性从DDT充电废水流出的帕洛斯弗迪斯大陆架和历史上未受污染的海底，提供一个？不自然？生物扰动效应的实验。使用随机模拟和可能性分析的贝壳年龄的频率分布，以及传统的统计分析的实验结果，该项目将确定的主导机制，确定壳保存，这是相关的生态保真度以及时间分辨率的骨骼组合在深和近时间的化石记录。更广泛的影响，我们将开发和完善协议，合并生物信息从古生物学和新生物学来源，作为保护古生物学的新兴领域的一部分。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，以促进科学整合。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成果。从我们的核心存档骨骼组合将构成一个新的资源，为未来的研究不同类型（例如，形态学，sclerochronology，同位素，分子），特别是当结合广泛的混合层死亡组合，我们已经存档从过去（20世纪70年代）和正在进行（2003年？目前）的调查和生物监测。该项目将为一名博士后学者以及来自一个历史悠久的黑人机构（萨凡纳州）的本科生和研究生助理提供实地和实验室经验。我们还将开发一个实验室练习，供当地高中和2年制或4年制大学使用，内容涉及南加州海洋海湾的历史生态学以及沉积岩芯在环境和生态分析中的作用。该区域公众对沿海环境质量有着强烈的兴趣，政府也对这一问题作出了承诺，因此，该区域现有良好的基础设施可供公众宣传。

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.