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

海洋环境的日益城市化对海洋人口构成了风险。干扰的种群后果(PCoD)模型是一个概念模型框架，旨在预测人为干扰对包括海洋哺乳动物在内的海洋种群的行为和生理的机械影响。目前，量化干扰的主要指标是行为变化，这意味着在PCoD模型中缺乏经验数据来参数化生理健康后果。海洋哺乳动物具有特殊的解剖和生理适应能力，能够耐受长时间的呼吸暂停(即屏气)，使它们对干扰敏感，因为这可能会挑战生理动态平衡，影响它们潜水、觅食和恢复的能力。先前的研究表明，海洋哺乳动物在经历了运动需要氧气的干扰事件后，可能会同时经历战斗和逃跑反应，但不会发生适应氧气需求的必要心血管反应。这种矛盾的反应可能导致缺氧(低血氧)和高二氧化碳(二氧化碳增加)，统称为窒息。鉴于生理监测的技术和后勤能力有限，海洋哺乳动物因受到干扰而窒息的后果尚不清楚。该项目旨在通过衡量干扰对海洋哺乳动物的生理后果以及它们与行为和觅食能量学的相互作用来告知这一知识差距，以便将生理和健康部分纳入种群模型框架。这些数据将通过自愿潜水、暂时圈养的灰海豹在海洋哺乳动物研究中心的池塘设施中收集，海豹会反复潜水到喂食器，然后回到水面呼吸。海豹的生理状态将通过使用呼吸室来控制暴露在混合呼吸气体中：环境、低氧和高碳酸血症，而不会使海豹暴露在干扰刺激下。改变血气对(1)心血管调节和器官功能以及(2)能量的影响将使用该实验装置进行测量。心血管功能和血气将通过可穿戴的、非侵入性的连续波近红外光谱(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记物，与近红外光谱数据相结合，以调查器官和组织动态平衡的变化。潜水和捕食猎物所需的能量消耗将使用潜水和恢复间隔时间来计算，以及通过平流式呼吸测量计算的总耗氧量和二氧化碳产生。总而言之，这些指标将允许对能源消耗指标进行测试和校准，这些指标可以纳入未来实地部署的近红外标签的机载数据处理中。最后，生理和能量结果将被合并到现有的PCoD模型中，以预测干扰的个人和种群水平的后果。

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.