Exploring functional interfaces: extreme biogenic fluctuations may amplify or buffer environmental stress on organisms associated with marine macrophytes

该项目的总体目标是通过在与生物相关的尺度上评估环境的强烈生物波动对压力调节的能力，来完善我们对沿海生态系统对预测的全球变化情景的反应的理解。沿海社区往往受到季节性或昼夜事件（例如水混合、潮汐、初级生产）造成的强烈环境波动的影响。这种波动强度随空间尺度的减小而增大，在覆盖大型植物表面的亚mm扩散边界层（DBL）中波动强度极高。这些波动，例如温度、pH值、CO2和O2的波动，往往比全球变化过程中预测的变化幅度大得多。它们可以暂时躲避环境压力，也可以使生物体适应环境变化。沿海底栖生物应对这种环境波动的机制实际上尚未得到研究。居住在DBL的表层生物，包括钙化苔藓虫、管虫和珊瑚藻，根据大型植物的代谢活动（光合作用和呼吸速率）和环境条件，经历了强烈但暂时不稳定的O2、CO2和H+ (pH)浓度梯度和极端（初步研究）。这些生物波动有可能掩盖、放大或缓冲包括全球变化压力在内的环境压力。考虑到大型植物（如海草、海带、海带）作为多样性和生产性沿海生态系统的生物工程师的重要性，以及它们所支持的多样性和生态重要性的表观生物，研究它们在全球变化下的相互作用具有重要意义。因此，该项目的具体目标是：(i)描述不同全球变化情景（变暖、海洋酸化、缺氧）下大型植物DBL的动态特征，（ii）调查其对钙化表观生物的影响及其适应或适应强烈波动状态的能力。（iii）确定表层植物对不同微生境的潜在预适应能力（大型植物vs.惰性表面DBL）； （iv）评估大型植物为海洋酸化和缺氧提供暂时庇护的潜力。结果预计将揭示生物体应对波动的机制及其对全球变化的耐受性，而后者可能与基于传统的稳态开放海洋全球变化实验的结果有很大不同。

The overarching aim of the project is to refine our understanding of coastal ecosystem responses to predicted Global Change scenarios by evaluating the capacity of stress-modulation by strong biogenic fluctuations of the environment at an organism-relevant scale. Coastal communities are often exposed to strong environmental fluctuations due to seasonal or diurnal events (e.g. water mixing, tides, primary production). The intensity of such fluctuations tends to increase with decreasing spatial scale and is extremely high in the sub-mm diffusive boundary layer (DBL) covering macrophyte surfaces. These fluctuations, in, for example, temperature, pH, CO2 and O2, are often of much greater magnitude than predicted changes in the course of Global Change. They may either offer temporal refuges from environmental stress or they may harden organisms to environmental changes. The mechanism of coastal benthic organisms to cope with such environmental fluctuations is virtually unstudied. Epibionts inhabiting the DBL including calcifying bryozoans, tube worms and coralline algae experience strong but temporally instable gradients in and extremes of O2, CO2 and H+ (pH) concentrations depending on the macrophytes metabolic activity (photosynthesis and respiration rates) and ambient conditions (pilot study). These biogenic fluctuations have the potential to mask, amplify or buffer environmental stress including Global Change pressures. Considering the importance of macrophytes (e.g. seagrass, kelp, bladder wreck) as bioengineers of diverse and productive coastal ecosystems and the diverse and ecologically important epibionts they support, it is of primordial importance to investigate their interaction under Global Change. Therefore, the specific aims of this project are (i) to characterize the dynamics of the DBL of macrophytes under different Global Change scenarios (warming, ocean acidification, hypoxia), (ii) to investigate its effect on calcifying epibionts and their ability to acclimatize or adapt to a strongly fluctuating regime, (iii) to identify potential pre-adaptation of epibionts to different micro-habitats (macrophyte vs. inert surface DBL) and (iv) to assess the potential of macrophytes to provide temporal refuge from ocean acidification and hypoxia. Results are expected to shed light on mechanisms of organisms to cope with fluctuations and their tolerance towards Global Change, while latter may differ significantly from results based on traditional steady-state open-ocean Global Change experiments.