Determining the dynamics of the colonization of the pelagic realm and evolution of the early Palaeozoic biological pump

自第一批动物进化以来，生物泵一直是支持海洋生物多样性的关键。该泵将海洋表面附近初级生产者固定的营养物质输送到各种海底动物群落，并促进深海的氧化。动物与生物泵的共同进化建立了更有效的营养循环，是早古生代动物多样化的关键因素。5.2亿年前，mya）。在整个动物历史中，生物泵一直控制着海洋生物圈的组成和生态结构，其崩溃与大规模灭绝事件有关。生活在水柱（远洋）中的动物对现代生物泵中营养物质的垂直运输至关重要，其中节肢动物在过去5亿年中占主导地位。节肢动物（包括现代千足虫、虾和昆虫）主宰着海洋生物量，消耗浮游植物并相互消耗。它们将尸体和粪便颗粒变成下沉的聚集体，并在水柱中垂直移动，为深水生态系统提供燃料。在古生代早期，节肢动物第一次在远洋领域定居，可能对加强生物泵和推动早期动物的多样化至关重要。化石记录提供的证据表明，节肢动物在寒武纪（5.2亿年）建立动物为主的生物泵至关重要，并在奥陶纪（4.9亿年）加强。然而，我们对节肢动物在远洋领域定居的克里思和动态的了解是不完整的。这是因为确定是否灭绝的动物是远洋或底栖依赖于结合多种来源的数据有关的动物的形态，以及地质背景下，不是所有这些都是可用于所有species.I将应用贝叶斯网络的方法来定量评估生态灭绝节肢动物和确定其变化的贡献，通过早期古生代的远洋境界。这种方法结合了化石数据（例如，地质背景，形态学）和生态学（例如，浮游/底栖，摄食模式），客观地为灭绝的动物指定了一种生活模式。该网络将使用来自现代节肢动物（例如，lophogastrids，phyllocarids，介形类）的数据进行“训练”，并应用于形态相似的古生代形式（例如，双瓣节肢动物、bradoriids、phosphatocopines、介形类）。由于这种方法可以处理丢失的数据，从而利用不太知名的和保存较差的类群，我将构建一个高时间分辨率的记录的生活方式的大型和小型灭绝节肢动物，从而确定的克里思和动力学的远洋领域的殖民化，这个生态上重要的门。因此，我将提供第一个定量评估的多样性，在远洋领域在广泛的时间尺度，包括寒武纪爆发和奥陶纪生物多样性大事件，以及恢复期后的主要质量灭绝（奥陶纪末和二叠纪-三叠纪）。因此，我将研究节肢动物对远洋领域的贡献的变化和第一个生物泵的进化，确定在大规模灭绝后恢复的速度，以及它对生活在海底附近的动物多样性的影响。这不仅对理解动物的共同进化和第一个以动物为主的生物泵有意义，而且还可以用来预测人类对海洋的影响以及海洋酸化和过度捕捞对生物多样性的连锁反应。

The biological pump has been critical for supporting biodiverse life in the oceans since the first animals evolved. This pump transports nutrients fixed by primary producers near the ocean surface to diverse bottom dwelling animal communities, and facilitates the oxygenation of the deep sea. The coevolution of animals with the biological pump established more efficient nutrient cycling, and was a key factor for the diversification of animals during the early Palaeozoic (c. 520 million years ago, mya). Throughout animal history, the biological pump has controlled the composition and ecological structure of the marine biosphere, and its breakdown is associated with mass extinction events.Animals that live in the water column (pelagic) are crucial for the vertical transport of nutrients in the modern biological pump, with arthropods a dominant component for the last 500 million years. Arthropods (a group that includes modern millipedes, shrimp and insects) dominate marine biomass, consuming phytoplankton and each other. They contribute carcasses and faecal pellets to sinking aggregates and move vertically in the water column, fuelling deep water ecosystems. The first colonization of the pelagic realm by arthropods in the early Palaeozoic was likely critical to strengthening the biological pump and driving the diversification of early animals. The fossil record provides evidence that arthropods were critical to establishing an animal-dominated biological pump in the Cambrian (520 mya), and its strengthening in the Ordovician (490 mya). However, our understanding of the tempo and dynamics of the colonization of the pelagic realm by arthropods is incomplete. This is because determining whether extinct animals were pelagic or benthic relies on combining multiple sources of data relating to the morphology of the animal, as well as geological context, not all of which are available for all species.I will apply a Bayesian network approach to quantitatively assess the ecology of extinct arthropods and determine their changing contribution to the pelagic realm through the early Palaeozoic. This approach combines fossil data (e.g., geological context, morphology) and ecology (e.g., pelagic/benthic, feeding mode), objectively assigning a life mode for extinct animals. The network will be 'trained' using data from modern arthropods (e.g. lophogastrids, phyllocarids, ostracods), and applied to morphologically-similar Palaeozoic forms (e.g., bivalved arthropods, bradoriids, phosphatocopines, ostracods). As this approach can handle missing data, and thus utilize less well known and more poorly preserved taxa, I will construct a high temporal resolution record of the life mode of large and small extinct arthropods, thus determining the tempo and dynamics of the colonization of the pelagic realm by this ecologically important phylum. Thereby I will provide the first quantitative assessment of the diversity of arthropods in the pelagic realm over broad timescales, covering the Cambrian explosion and Great Ordovician Biodiversification Event, as well as the recovery periods after major mass extinctions (end Ordovician and Permian-Triassic).Thus, I will investigate the changing contribution of arthropods to the pelagic realm and evolution of the first biological pump, determine how quickly it recovered after mass extinctions, and its impact on the diversity of animals living close to the seafloor. This has implications not just for understanding the coevolution of animals and the first animal-dominated biological pump, but can also be used to make predictions about the impact of humans on the oceans and the knock-on effects of ocean acidification and overfishing on biodiversity.