CAREER: Quantifying Western Atlantic Climate and Seasonality across the Plio-Pleistocene Regional Molluscan Extinction

在过去的400万年里，70%-80%的软体动物物种(文蛤、扇贝等)生活在大西洋和墨西哥湾沿岸水域的它们已经消失了。新物种的诞生是为了取代那些灭绝的物种，软体动物的种群在今天仍然相当多样化。物种大量更替的原因还没有确定。主要的假设是，不断下降的水温赶走了喜欢温暖水域的物种，取而代之的是那些可以生活在较凉爽水域的物种。研究人员将对过去300-500万年来东海岸上下的地点进行可靠的、定量的温度估计，并将这些估计与海洋软体动物的灭绝模式进行比较，以检验这一假设。除了解决物种灭绝的根本原因外，这些数据还将揭示有关所研究软体动物物种耐热性的信息，并确定这些耐热性是固定的还是灵活的(这意味着一个物种可以适应与其目前栖息的水温不同的水温)。这将对生活在美国水域的软体动物的生存产生影响，在未来几十年和几个世纪里，随着海洋温度的上升，这些软体动物(包括那些被养殖用于水产养殖的贝类和扇贝)将受到影响。研究人员将通过与密歇根大学自然历史博物馆合作的一些外展项目和展品与公众分享他们的发现。他们将创建一门真实的研究体验课程，以降低进入门槛的方式向更多本科生介绍研究，特别是对代表不足的群体。研究人员将使用集束同位素古温度计(D47)对软体动物化石进行同位素测量，包括对现代海洋腹足类和双壳类进行校准。这一新方法的使用是至关重要的，因为基于d47的初步温度估计与基于氧同位素的历史估计有很大不同，后者由于对过去海水氧同位素组成(D18Osw)的限制较差而存在缺陷。这里产生的数据将通过确定热容忍度随时间和空间的变化(或缺乏)来直接解决软体动物分类群的生态位稳定性问题。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Over the past ~4 million years, 70-80% of mollusk species (clams, scallops, etc.) living in the waters of the Atlantic & Gulf Coasts have disappeared. New species originated to replace those that went extinct, and the mollusk population remains quite diverse today. The cause of this great turnover in species has not been established. The primary hypothesis is that declining water temperatures pushed out warm-water-loving species and replaced them with those that could inhabit cooler waters. The researcher will produce robust, quantitative temperature estimates from sites up and down the East Coast over the past 3-5 million years and compare those to extinction patterns of marine mollusks to test this hypothesis. In addition to addressing the root cause of the extinction, these data will reveal information about the thermal tolerances of studied mollusk species and determine whether those are fixed or flexible (meaning a species could adapt to live in different water temperatures than it currently inhabits). This will have implications for the survival of mollusks living in American waters (including those farmed for aquaculture like clams and scallops) in the coming decades and centuries as ocean temperatures warm. The researcher will share their findings with the public through a number of outreach projects and exhibits in partnership with the UMich Museum of Natural History. They will create an authentic research experience course to introduce more undergraduates to research in a way that lowers barriers-to-entry, especially for underrepresented groups. The researcher will conduct a program of isotopic measurements on fossil mollusks using the clumped isotope paleothermometer (D47), including calibrations of modern marine gastropods and bivalves. Use of this new method is vital, as preliminary D47-based temperature estimates differ greatly from historical oxygen-isotope-based estimates which are flawed due to their poor constraints on past oxygen isotopic composition of seawater (d18Osw). Data generated here will directly address questions of niche stability in mollusk taxa through determination of changes (or lack thereof) in thermal tolerances over time and space.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.