Biotic and abiotic drivers of pathogen transmission in marine system under the influence of climate change

海洋系统中出现的病原体通过破坏渔业及其支持的生态群落而影响到我们所有人。事实上，两个地区的标志，蓝蟹和牡蛎，由于疾病已经出现了严重的下降。这项研究的目的是了解气候变化和其他人类影响如何改变海洋系统中的疾病传播。美国蓝蟹（Callinectes sapidus）与滤食、同类相食、捕捞压力和气候变化的关系将被研究。滤食在海洋系统中广泛存在，可能起到减少病原体传播的作用。同类相食可以减少易受感染的幼蟹，从而降低传播。因为捕鱼的压力会使成年蟹消失，对抗同类相食，商业捕鱼可能会增加易受感染的幼蟹，并增加螃蟹种群的传播。这些生物因素在许多海洋系统中是共同的；然而，就它们对疾病传播的影响而言，它们很少受到关注。气候变化通过对宿主和病原体动态的直接和间接影响放大了这些动态。该项目以其研究活动为基础，让教师和学生参与海洋生物学、疾病生态学和气候变化等重要概念的学习。科学教师将参与实习、研讨会和实地课程，以利用项目的研究成果在课堂上传播。教育部分将通过多个学科的先进技术培训，培养William & Mary和VIMS的教师、研究生、本科生暑期实习生和本科生的能力。一个在线模型将模拟疾病对海洋系统的影响，使科学家、教育工作者和学生更容易获得研究结果。每个机构的外展项目将进一步让成千上万的人了解该项目的研究。总的来说，这些活动将提高这项研究对更广泛的科学界、教育界和公众的可见度。海洋和陆地生态系统之间的疾病过程可能非常不同。在海洋系统中，生物因素，如通过滤食对浮游植物自上而下的控制、捕食者种群的依赖于密度的同类相食、工业化捕鱼等，在大尺度上起着改变宿主种群动态的作用；然而，它们对疾病生态的影响却很少受到关注。一项对蓝蟹-佩雷兹血球系统的调查，让我们深入了解了这些因素之间的相互作用。佩雷齐血液病是蓝蟹的一种病原体，在美国东部沿海海湾高度流行。这种病原体偏爱幼蟹。同类相食会消灭大量幼鱼，潜在地抑制爆发。相反，捕捞压力使大量成鱼消失，潜在地增加了易受影响的幼鱼数量。此外，牡蛎的滤食可能会减少H. perezi的传播，并且当牡蛎礁等高丰度时，可能会对蓝蟹的疾病传播产生负面影响。凌驾于这些因素之上的是气候变化造成的生态系统层面的破坏，其中包括通过增加扩散和扩散进一步加强病原体传播。这些因素可以建模，以深入了解它们对宿主-病原体动力学的影响。本研究有五个目标：(1)将疾病和季节性纳入蓝蟹种群模型；（II）研究生态系统中滤食性动物与病原体传播之间的相互作用；（III）探索自然死亡率（捕食、同类相食）和捕捞压力如何影响病原体的传播和发病率；（四）研究气候变化对疾病传播和扩散的影响；(V)分析非线性机制，以便更广泛地应用于野生动物疾病动力学。虽然本研究关注的是蓝蟹-佩雷兹血液病系统的传播动力学，但也适用于其他受到类似应激源影响的海洋系统。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The emergence of pathogens in marine systems affects us all by damaging fisheries and their supporting ecological communities. Indeed, two regional icons, blue crabs and oysters, have seen major declines due to disease. The goal of this study is to understand how climate change and other human impacts alter disease transmission in marine systems. The transmission of a pathogen, Hematodinium perezi, to the American blue crab, Callinectes sapidus will be examined in relation to filter feeding, cannibalism, fishing pressure, and climate change. Filter feeding is widespread in marine systems and may act to reduce transmission of pathogens. Cannibalism may reduce susceptible juvenile crabs and, thus, lower transmission. Because fishing pressure removes adults, countering cannibalism, commercial fishing may enhance susceptible juveniles and increase transmission in crab populations. These biotic factors are common to many marine systems; yet, they have received little attention in terms of their effects on disease transmission. Climate change magnifies these dynamics through direct and indirect effects on both the host and pathogen dynamics. This project builds on its research activities by engaging teachers and students in important concepts in marine biology, disease ecology, and climate change. Science teachers will engage in internships, workshops, and field courses to leverage the project’s research findings for delivery in the classroom. The educational component will build the capabilities of teachers, graduate students, undergraduate summer interns, and undergraduates at William & Mary and VIMS through training in advanced techniques in several disciplines. An online model will simulate the effects of disease on marine systems, making the research findings even more accessible to scientists, educators, and students. Outreach programs at each institution will further inform thousands of people about the project’s research. Collectively, these activities will enhance the visibility of this research to the broader scientific community, educational community, and general public.Disease processes can be very different between marine and terrestrial ecosystems. In marine systems, biotic factors such as top-down control of phytoplankton through filter feeding, density-dependent cannibalism in predator populations, and industrialized fishing operate on grand scales that alter the dynamics of host populations; however, their influence on disease ecology has received little attention. An investigation into the blue crab – Hematodinium perezi system allows insights into the interactions among these factors. Hematodinium perezi is a pathogen of blue crabs that is hyper-endemic in the coastal bays of the eastern USA. The pathogen has a predilection for juvenile crabs. Cannibalism removes large numbers of juveniles, potentially suppressing outbreaks. In contrast, fishing pressure removes large numbers of adults, potentially enhancing the susceptible juvenile population. In addition, filter feeding by oysters may reduce transmission of H. perezi, and when combined with high abundance such as in oyster reefs, may negatively influence disease transmission to blue crabs. Overlying these factors is the ecosystem-level disruption caused by climate change, which includes additional enhancements to pathogen transmission through increased proliferation and dispersal. These factors can be modeled to provide insight into their influence over host – pathogen dynamics. This study has five objectives: (I) integrate disease and seasonality into a population model of the blue crab; (II) examine the interactions between filter feeders in the ecosystem and pathogen transmission; (III) explore how natural mortality (predation, cannibalism) and fishing pressure affect transmission and incidence of the pathogen; (IV) examine the influence of climate change on disease transmission and dispersal; and (V) analyze nonlinear mechanisms for broader application to wildlife disease dynamics. Although this study focuses on the transmission dynamics in the blue crab – Hematodinium perezi system, it is applicable to other marine systems impacted by similar stressors.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.