Predicting physiological impacts of disturbance on marine mammals: Implications for population-level effects

海洋环境日益城市化对海洋种群构成了威胁。种群干扰后果（PCoD）模型是一个概念性建模框架，旨在预测人为干扰对海洋种群（包括海洋哺乳动物）行为和生理的机制影响。目前，量化干扰的主要指标是行为变化，这意味着缺乏经验数据来参数化PCoD模型中的生理健康后果。海洋哺乳动物具有特殊的解剖和生理适应性，可以忍受长时间的呼吸暂停（即屏气），这使它们对干扰非常敏感，因为这可能会挑战生理稳态，影响它们潜水、觅食和恢复的能力。先前的研究表明，海洋哺乳动物可能会在运动中需要氧气的干扰事件后同时经历战斗和逃跑反应，但必要的心血管反应不会发生以适应氧气需求。这种矛盾的反应可能导致缺氧（低血氧）和高碳酸血症（二氧化碳增加）；统称为窒息。由于生理监测的技术和后勤能力有限，对海洋哺乳动物干扰的窒息后果尚不清楚。该项目旨在通过测量干扰对海洋哺乳动物的生理后果及其与行为和觅食能量学的相互作用来了解这一知识差距，以便将生理和健康因素纳入种群建模框架。这些数据将在海洋哺乳动物研究中心（Sea Mammal Research Unit）的水池设施中使用自愿潜水、暂时圈养的灰海豹来收集，在那里，海豹会反复潜入喂食器，然后回到水面呼吸。通过使用呼吸室来控制呼吸气体混合物的暴露：环境，缺氧和高碳酸血症，可以在不使密封件暴露于干扰刺激的情况下操纵密封件的生理状态。改变血气对(1)心血管调节和器官功能以及(2)能量学的影响将使用这个实验装置来测量。心血管功能和血气将通过可穿戴、非侵入式连续波近红外光谱（NIRS）标签进行测量。此外，潜水前后的静脉血采样将提供轻度创伤性脑损伤、氧化应激和炎症的血液生物标志物，并结合近红外光谱数据来研究器官和组织稳态的变化。潜水和消耗猎物所需的能量消耗将通过潜水和恢复间隔时间来计算，以及通过开放流呼吸法计算出的总耗氧量和二氧化碳产量。总之，这些指标将允许测试和校准能量消耗指标，这些指标可以整合到NIRS标签的机载数据处理中，以供未来的现场部署。最后，生理和能量结果将被纳入现有的PCoD模型，以预测个体和群体水平的干扰后果。

The increasing urbanisation of marine environments poses a risk for marine populations. The Population Consequences of Disturbance (PCoD) model is a conceptual modelling framework that aims to predict the mechanistic effects of anthropogenic disturbance on the behaviour and physiology of marine populations, including marine mammals. Currently, the primary metrics for quantifying disturbance are behavioural changes, meaning there is a lack of empirical data to parameterise physiological health consequences in the PCoD model. Marine mammals have specialised anatomical and physiological adaptations to endure long periods of apnoea (i.e. breath-holding) making them sensitive to disturbance, as it could challenge physiological homeostasis and affect their ability to dive, forage, and recover. Previous research suggests that marine mammals may experience a simultaneous fight and flight response following a disturbance event in which oxygen is required for exercise, but the necessary cardiovascular responses to accommodate the oxygen demand do not occur. This paradoxical response may result in hypoxia (low blood oxygen) and hypercapnia (increased carbon dioxide); collectively called asphyxia. Given the limited technological and logistical capabilities for physiological monitoring, the consequences of asphyxia in response to disturbance of marine mammals are unknown. This project aims to inform this knowledge gap by measuring physiological consequences of disturbance to marine mammals and their interaction with behaviour and foraging energetics in order to integrate physiological and health components to population modelling frameworks. The data will be collected using voluntarily diving, temporarily captive, grey seals at the Sea Mammal Research Unit's pool facility, in which seals make repeated dives to a feeder and back to the surface to breathe. The physiological state of the seals will be manipulated without exposing seals to disturbance stimuli by using a breathing chamber to control exposure to respiratory gas mixes: ambient, hypoxic, and hypercapnic. The effect of changing blood gases on (1) cardiovascular regulation and organ function and (2) energetics will be measured using this experimental setup. Cardiovascular function and blood gases will be measured by wearable, non-invasive continuous-wave near infrared spectroscopy (NIRS) tags. Additionally, venous blood sampling before and after diving trails will provide blood biomarkers of mild traumatic brain injury, oxidative stress, and inflammation to be combined with NIRS data to investigate changes to organ and tissue homeostasis. Energy expenditure required to dive and consume prey will be calculated using dive and recovery interval durations, as well as total oxygen consumption and carbon dioxide production calculated from open-flow respirometry. Together, these metrics will allow for testing and calibration of metrics for energy expenditure that can be incorporated into onboard data processing of NIRS tags for future field deployments. Finally, the physiological and energetic outcomes will be incorporated to existing PCoD models to predict individual and population level consequences of disturbance.